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Zihan Zhang, Xingxin Jiang, [Nattapol Ma](https://orcid.org/0000-0002-6162-1834), [Jizhen Zhang](https://orcid.org/0000-0002-9584-9554), Emmanuel Picheau, [Nobuyuki Sakai](https://orcid.org/0000-0002-9395-6751), [Takayoshi Sasaki](https://orcid.org/0000-0002-2872-0427), [Renzhi Ma](https://orcid.org/0000-0001-7126-2006)

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[Composition- and structure-tunable CoNiFe hydroxide nanostructures toward enhanced oxygen evolution reaction](https://mdr.nims.go.jp/datasets/3f528201-67a8-4e89-9c11-39ff3a7872aa)

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Composition- and structure-tunable CoNiFe hydroxide nanostructures toward enhanced oxygen evolution reactionNanoscalePAPERCite this: Nanoscale, 2026, 18, 13397Received 20th January 2026,Accepted 10th May 2026DOI: 10.1039/d6nr00271drsc.li/nanoscaleComposition- and structure-tunable CoNiFehydroxide nanostructures toward enhancedoxygen evolution reactionZihan Zhang,a,b Xingxin Jiang,a,b Nattapol Ma, c Jizhen Zhang, aEmmanuel Picheau,a Nobuyuki Sakai, a Takayoshi Sasaki a and Renzhi Ma *a,bThe electrocatalytic performance of transition-metal layered double hydroxides (LDHs) can be substan-tially enhanced through compositional and structural engineering. Herein, ternary (CoNiFe) hydroxidenanocones featuring mixed tetrahedral (Td) and octahedral (Oh) coordination are rationally designed toboost oxygen evolution reaction (OER) activity. Binary CoNi hydroxide nanocones with mixed coordi-nation are first synthesized, among which a Co : Ni ratio of 3 : 1 exhibits optimal performance with anoverpotential of 339 mV at 10 mA cm−2. Subsequent Fe incorporation followed by a topochemical oxi-dative intercalation process convert the CoNiFe(II) hydroxides into CoNiFe(III) LDHs while retaining mixedTd/Oh coordination. Benefiting from the synergistic effects of multimetal composition and coordinationmodulation, the resulting Co3Ni1Fe1 LDH nanocones achieve a markedly reduced overpotential of280 mV. Furthermore, exfoliation into monolayer nanosheets leads to a further enhancement in catalyticactivity by increasing exposure of accessible active sites, ultimately lowering the overpotential to 267 mV.This study highlights an effective strategy that integrates compositional optimization, coordination engin-eering, and structural modulation for the development of high-performance LDH electrocatalysts.1. IntroductionHydrogen is widely regarded as a promising energy carrierowing to its high gravimetric energy density, carbon-free utiliz-ation, and broad applicability across energy and industrialsectors.1–3 Among various hydrogen production routes, electro-chemical water splitting is considered a clean and efficientapproach.4–6 Nevertheless, the overall efficiency of water elec-trolysis is severely constrained by the oxygen evolution reaction(OER) at the anode, which involves a complex four-electrontransfer process and high-energy reaction intermediates,resulting in large overpotentials and significant energylosses.7–9 Although noble-metal-based catalysts such as RuO2and IrO2 exhibit excellent OER activity and are commonlyregarded as benchmark materials, their high cost, scarcity,and limited durability hinder widespread practical application,underscoring the need for cost-effective alternatives with com-parable performance.10–12 Consequently, the exploration ofefficient and Earth-abundant OER electrocatalysts is crucial forimproving electrolysis efficiency and enabling large-scalehydrogen production.Catalysts based on Earth-abundant transition metals,especially Fe, Co, Ni, and Mn, have gained increasing attentionas promising substitutes for noble metals.13–17 Among them,layered double hydroxides (LDHs) are especially appealing dueto their highly tunable compositions, flexible layered architec-tures, and intrinsically abundant active sites.18–20 In particular,Co-based LDHs have demonstrated superior catalytic activity,which is often attributed to their favorable electronic structureand versatile redox chemistry, making them highly effective forthe OER.21–23 Considerable efforts have been devoted toenhancing the catalytic activity of LDHs, among which struc-tural and morphological engineering have emerged as a par-ticularly effective strategy.24,25 The construction of well-definednanostructures with controlled geometries, such as nanocones(NCs), enables effective regulation of the surface curvature andspatial distribution of active sites. These nanocone mor-phologies not only increase the exposed surface area but alsofacilitate mass transport and electron transfer, while mitigat-ing stacking and aggregation issues commonly associated withlayered materials.26–29 Notably, the NCs belong to the so-calledα phase featuring a unique coexistence of mixed tetrahedral(Td) and octahedral (Oh) coordination and can be topochemi-cally transformed into LDHs.30–32 Compared with conventionalaResearch Center for Materials Nanoarchitectonics (MANA), National Institute forMaterials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.E-mail: MA.Renzhi@nims.go.jpbGraduate School of Advanced Science and Engineering, Waseda University, 3-4-1Okubo, Shinjuku-ku, Tokyo 169-8555, JapancInternational Center for Young Scientists (ICYS), National Institute for MaterialsScience (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, JapanThis journal is © The Royal Society of Chemistry 2026 Nanoscale, 2026, 18, 13397–13408 | 13397Published on 12 May 2026Licensed under CC-BY-NC 4.0http://rsc.li/nanoscalehttp://orcid.org/0000-0002-6162-1834http://orcid.org/0000-0002-9584-9554http://orcid.org/0000-0002-9395-6751http://orcid.org/0000-0002-2872-0427http://orcid.org/0000-0001-7126-2006http://crossmark.crossref.org/dialog/?doi=10.1039/d6nr00271d&domain=pdf&date_stamp=2026-06-30https://creativecommons.org/licenses/by-nc/4.0/LDHs containing exclusively octahedrally coordinated metalcenters, this mixed coordination configuration enriches thediversity of active sites and contributes to improved catalytic per-formance.32 In recent years, expanding binary LDHs to ternaryor multimetal systems has proven to be an effective strategy forfurther boosting OER performance.33–35 The introduction ofadditional metal species can modulate the local electronic struc-ture through cooperative cation–cation interactions, enablingprecise regulation of coordination environments and valencestates.36–39 Notably, Fe incorporation into Co- and Ni-basedhydroxides/LDHs has been widely reported to induce electronicredistribution among metal centers, thereby optimizing theadsorption and conversion of oxygenated intermediates andultimately enhancing OER kinetics.40–43In this work, ternary CoNiFe layered hydroxide NCs withmixed Td and Oh coordination were designed to systematicallyinvestigate the synergistic effects of composition, coordinationconfiguration, and morphology on OER performance. BinaryCoNi hydroxide NCs with mixed coordination were first syn-thesized, followed by the incorporation of Fe to developternary CoNiFe systems. Subsequently, a topochemical oxi-dative intercalation process using iodine converted theα-phase hydroxides into LDHs (LDHTd/Oh). By systematicallycomparing binary and ternary compositions, the role of hetero-atom incorporation and coordination modulation in governingelectrocatalytic behavior was elucidated. Furthermore, thenanocone-derived LDHTd/Ohwas exfoliated into monolayernanosheets (NSs) to explore the impact of dimensionalreduction on OER activity. This study provides a rationalframework for tailoring layered hydroxide electrocatalyststhrough integrated compositional coordination, and structuralengineering.2. Experimental section2.1. Synthesis of binary CoNi hydroxide NCsCoNi hydroxide NCs were obtained through homogeneous pre-cipitation based on our earlier method with slight modifi-cations.27 Designated amounts of CoCl2·6H2O, 70 mmol urea,and 25 mmol sodium dodecyl sulfate (SDS) were dissolved in1000 mL of deaerated water in a three-neck round-bottom flask.A NiCl2 solution was also prepared and stored in a pressure-equalizing dropping funnel, which was attached to one of thenecks. The total amount of metal precursors (CoCl2·6H2O andNiCl2·6H2O) was controlled at 10 mmol with varied Co/Ni ratios(4 : 1, 3 : 1, 2 : 1, and 1 : 1). The flask was then heated in an oilbath to 110 °C and kept under a nitrogen atmosphere for reflux.After refluxing for 5 h, the NiCl2 solution in the funnel wasdropped into the flask. The synthesis proceeded for a total of8 h. Upon completion, the solid products were isolated andwashed repeatedly using water and ethanol.2.2. Synthesis of ternary CoNiFe(II) hydroxide NCsThe preparation route for the ternary hydroxide is similar tothe procedure developed for the binary system, with the totalamount of metal precursors (CoCl2·6H2O, NiCl2·6H2O, andFeCl2·4H2O) controlled at 10 mmol. CoCl2·6H2O, urea(70 mmol), and SDS (25 mmol) were dissolved in 1000 mL ofdeaerated water in a four-neck round-bottom flask. In parallel,aqueous solutions of NiCl2·6H2O and FeCl2·4H2O were indivi-dually dissolved in 50 mL of water and transferred into separ-ate pressure-equalizing dropping funnels. CoNiFe(II) hydroxideNCs were synthesized with a series of Co : Ni : Fe molar ratios,including 8 : 1 : 1, 7 : 2 : 1, 7 : 2 : 2, 3 : 1 : 1, 7 : 1 : 2, and 6 : 1 : 3.After approximately 1.5 h of refluxing, the FeCl2 solution wasintroduced into the flask, followed by the addition of the NiCl2solution when the reaction time reached 5 h.2.3. Synthesis and exfoliation of ternary CoNiFe(III) LDHTd/OhNCsThe as-prepared NCs were subsequently transformed intoLDHTd/Ohthrough a topochemical oxidative intercalationprocess following established protocols.32,44 In a typical pro-cedure, 0.5 g of the CoNiFe(II) hydroxide NCs was introducedinto 100 mL of I2/CHCl3 solution and kept under continuousstirring for about 24 h. After the reaction, the oxidizedLDHTd/Ohproducts were collected by filtration and thoroughlyrinsed with CHCl3 and ethanol until the filtrate became clear.To exfoliate, 0.04 g of the resulting CoNiFe(III) LDHTd/Ohpowderwas dispersed in 100 mL of degassed formamide and sub-jected to sonication for 2 h. The mixture was centrifuged at3500 rpm for 30 min to remove any unexfoliated residues,yielding a translucent colloidal suspension.2.4. Electrochemical measurementsOER measurements were carried out using a standard three-electrode setup on a CH Instruments 760E electrochemicalworkstation (CHI 760E). For working electrode preparation,5 mg of catalyst was dispersed in 1 mL of a water/ethanolmixture (1 : 1, v/v) containing 10 μL of 10 wt% Nafion solution.The suspension was sonicated for 30 min to form a homo-geneous ink, after which 4 μL was deposited onto a polishedglassy carbon electrode (3 mm diameter) and dried at 60 °C.The resulting catalyst loading was approximately 0.23 mgcm−2. 1 M KOH was used as the electrolyte, with a Hg/HgOelectrode serving as the reference and a Pt wire as the counterelectrode. All potentials were calibrated to the reversible hydro-gen electrode (RHE) according to the equation:ERHE ðVÞ ¼ EHg=HgO ðVÞ þ 0:059 pHþ 0:098Cyclic voltammetry (CV) was initially performed at a scanrate of 30 mV s−1 from 0 to 0.8 V vs. Hg/HgO until stablecurves were obtained. Subsequently, linear sweep voltammetry(LSV) was carried out from 0 to 0.8 V vs. Hg/HgO at a scan rateof 5 mV s−1 with 95% manual iR-compensation. All electro-chemical measurements were repeated three times, and con-sistent results were obtained, confirming the reliability of thedata. Tafel slopes were derived from the Tafel equation.Electrochemical impedance spectroscopy (EIS) was conductedat 0.62 V vs. Hg/HgO within a frequency range of 0.1 to 105 Hzat an amplitude of 5 mV. CV tests were performed betweenPaper Nanoscale13398 | Nanoscale, 2026, 18, 13397–13408 This journal is © The Royal Society of Chemistry 20260.35 and 0.45 V vs. Hg/HgO at various scan rates (20, 40, 60,80, and 100 mV s−1). The slope of the plot of the currentdensity difference (Δj = ja − jc) at the midpoint of the potentialwindow against the scan rates was calculated to be twice thedouble-layer capacitance (Cdl), which was used to estimate theelectrochemical surface area (ECSA). For the purpose of exclud-ing the improvement by the ECSA, the OER performance wasnormalized by the ECSA. The ECSA-normalized current densityfor the as-prepared catalysts was calculated to be:ECSA-normalized current density ¼ current density � Cs=Cdlwhere Cs is the specific capacitance. In this work, 0.04 mFcm−2 was adopted as the value of Cs based on previouslyreported catalysts in alkaline solutions.45,462.5. Materials characterizationPowder X-ray diffraction (XRD) patterns were collected using aRigaku Ultima IV diffractometer equipped with Cu Kα radi-ation (λ = 0.15405 nm) operating at 40 kV and 40 mA. In-planeXRD measurements of NSs deposited on Si substrates wereperformed using synchrotron X-ray radiation (λ = 0.11988(2)nm) at the BL-6C beamline of the Photon Factory, High EnergyAccelerator Research Organization (KEK). Morphological andelemental analyses were performed by scanning electronmicroscopy (SEM, JEOL JSM-6010LA) coupled with energy-dis-persive X-ray spectroscopy (EDS). Selected area electron diffrac-tion (SAED) patterns as well as transmission electronmicroscopy (TEM) and high-resolution TEM (HRTEM) imageswere acquired using a JEOL JEM-2100 microscope operated ata 200 kV acceleration voltage. Atomic force microscopy (AFM)study of NSs on Si substrates was conducted in tapping modeusing a Hitachi AFM5000II system. Thermogravimetric (TG)analysis was carried out using a Rigaku TG-DTA8122 instru-ment. Brunauer–Emmett–Teller (BET) specific surface areaswere determined by N2 adsorption–desorption measurementsusing a Quantachrome Autosorb-1 analyzer. X-ray total scatter-ing and pair distribution function (PDF) analyses were per-formed on the BL04B2 beamline at the Super Photon Ring-8GeV (SPring-8) facility in Hyogo, Japan. The incident beamenergy was 112.9232 keV (λ = 0.109795 Å).3. Results and discussion3.1. Binary CoNi hydroxide NCsBinary CoNi hydroxide NCs were obtained by introducing Nispecies into preformed Co hydroxide NCs, as schematicallyillustrated in Fig. 1a. As shown in Fig. S1a, pristine Co hydrox-ide NCs display uniform cone-shaped morphologies with dis-tinct hollow interiors. Similar nanocone architectures wereobserved for Co4Ni1, Co3Ni1, and Co2Ni1 hydroxides (Fig. S1b–d), indicating that incorporating a moderate amount of Nidoes not disrupt the conical framework. Nevertheless, furtherincreasing the Ni proportion leads to a gradual deteriorationof the nanocone structure. For the Co1Ni1 sample (Fig. S1e),nanoplatelets emerge and partially decorate the surfaces of theNCs. In contrast, pure Ni hydroxide, as presented in Fig. S1f,predominantly exhibits a nanoplatelet-like morphology. Theseobservations indicate that maintaining a Co-rich compositionis essential for the formation and preservation of well-definednanocone architectures. The EDS analysis summarized inTable S1 confirms that the actual Co : Ni atomic ratios in theCoNi hydroxides closely match the targeted compositions. Asthe designed Co : Ni ratio decreases from 4 : 1 to 1 : 1, the Cocontent correspondingly decreases while the Ni fractionincreases. This composition evolution clearly indicates thatthe metal ions were successfully incorporated into the hydrox-ide framework, consistent with the designed stoichiometry.Fig. S2 presents the XRD patterns of CoNi hydroxide NCsprepared with different Co/Ni ratios. All compositions displaypronounced basal reflections corresponding to an interlayerspacing of 2.5 nm, which is characteristic of DS−-intercalatedα-phase hydroxides and substantially larger than that of con-ventional brucite-type hydroxides (0.46 nm). These results indi-Fig. 1 Synthesis of hydroxide NCs with different compositions. (a) Schematic illustration. SEM images of (b) Co hydroxide, (c) Co3Ni1 hydroxide, and(d) Co3Ni1Fe1(II) hydroxide.Nanoscale PaperThis journal is © The Royal Society of Chemistry 2026 Nanoscale, 2026, 18, 13397–13408 | 13399cate that the layered framework is well preserved upon Niincorporation. With increasing Ni content, both the 100 and110 reflections gradually shift toward higher diffraction angles,reflecting a contraction of the in-plane lattice parameter a.This trend is consistent with partial substitution by Ni2+,whose ionic radius (69 pm in Oh and 55 pm in Td) is smallerthan that of Co2+ (74 pm in Oh and 58 pm in Td). In contrast,pure Ni hydroxide exhibits two distinct sets of diffractionpeaks: one associated with a DS−-intercalated α phase and theother corresponding to a brucite-type structure without inter-calation of any interlayer anions. The coexistence of thebrucite phase likely originates from the limited ability of Ni2+to adopt Td coordination with DS−, which is crucial for the for-mation of the α-phase nanocone structure.3.2. Ternary CoNiFe(II) hydroxide NCsSEM images in Fig. 1b–d reveal that the three hydroxide pro-ducts retain well-defined nanocone architectures, demonstrat-ing that compositional tuning does not fundamentally alterthe overall morphology. Notably, the CoNiFe hydroxidesexhibit a slight degradation in the conical structure comparedwith their Co and CoNi counterparts, implying that multimetalincorporation influences the crystal growth behavior and nano-cone formation process. XRD patterns of the NCs withdifferent compositions, represented by Co3Ni1Fe1 hydroxide,Co3Ni1 hydroxide, and Co hydroxide, are shown in Fig. 2a. Allthe hydroxide NCs display a series of sharp 00l reflections,confirming the preservation of a well-defined layered structure.The low-angle basal reflections remain essentially unchangedacross different compositions, indicating that the introductionof Ni and Fe does not significantly affect the basal latticeframework. On the other hand, the enlarged views in Fig. 2band c reveal a slight shift of the 100 and 110 peaks towardhigher angles for CoNi hydroxide relative to Co hydroxide, indi-cating a contraction of in-plane lattice parameters induced byNi incorporation. In contrast, the in-plane peaks of CoNiFehydroxide shift to lower angles compared with those of CoNihydroxide, reflecting the lattice expansion resulting from thelarger ionic radius of Fe2+ (78 pm in Oh and 63 pm in Td) thanthose of Co2+ and Ni2+. The variations in lattice spacing there-fore confirm the successful incorporation of Ni and Fe into thehost layers, accompanied by corresponding modifications ofthe local coordination environment within the hydroxideframework.To probe the local atomic structure, PDF analysis was per-formed on hydroxides with different compositions. As shownin Fig. 2d, PDF profiles gradually decay with increasing r,which corresponds to longer-range atomic pair correlations inreal space, reflecting the finite structural coherence length ofthe nanostructured hydroxides. Moreover, the intensities inthe high-r region progressively weaken from Co hydroxide toCoNi hydroxide and further to CoNiFe hydroxide, indicating agradual reduction in long-range structural order upon multi-component incorporation.47 This attenuation of PDF oscil-lations suggests an increased degree of structural disorder anda shortened coherence length induced by the successive intro-duction of Ni and Fe.48,49 Such structural distortions areaccompanied by modifications in the local coordinationenvironment, which can alter the electronic structure of activesites and thereby influence the adsorption behavior of OERintermediates.25,35 The low-r region in Fig. 2e highlights dis-tinct coordination features, where the peak at approximatelyFig. 2 (a–c) XRD patterns of Co3Ni1Fe1 hydroxide, Co3Ni1 hydroxide, and Co hydroxide. PDF patterns of (d) high-r and (e) low-r regions.Paper Nanoscale13400 | Nanoscale, 2026, 18, 13397–13408 This journal is © The Royal Society of Chemistry 20262.0 Å is assigned to M–O bonds, while the peak near 3.0 Åarises from M–M atomic correlations. Compared with Cohydroxide, both the M–O and M–M peaks of CoNi hydroxideshift to slightly shorter distances, indicating lattice contractioninduced by Ni incorporation. In contrast, upon further intro-duction of Fe, the corresponding M–O and M–M peaks ofCoNiFe hydroxide shift toward longer distances relative tothose of CoNi hydroxide, reflecting lattice expansion. Thesesystematic shifts in both M–O and M–M distances unequivo-cally confirm the successful incorporation of Ni and Fe intothe host layers and the associated modification of the localcoordination environment, which are consistent with the XRDobservations.3.3. Ternary CoNiFe(III) LDH NCsA topochemical oxidation procedure shown in Fig. 3 wasemployed to transform the hydroxide NCs into an LDH phase.During this treatment, I2 served as an oxidizing agent toconvert Fe2+ into Fe3+, while I− anions were simultaneouslyintercalated into the interlayer galleries to maintain chargebalance. This process resulted in the formation of a CoNiFe(III)LDH with mixed Td and Oh coordination (referred to asCoNiFe LDHTd/Oh). Fig. S3 displays the structural evolution ofNCs prepared with a representative Co : Ni : Fe ratio of 3 : 1 : 1.XRD patterns along the c-axis exhibit negligible changes,which can be attributed to the smaller ionic radius of I− rela-tive to that of DS−, leading to minimal variation in the inter-layer spacing. In contrast, the in-plane 100 and 110 reflectionsof CoNiFe LDHTd/Ohshift to higher angles compared to thoseof CoNiFe hydroxide, originating from lattice contractioninduced by the oxidation of Fe2+ to Fe3+, as Fe3+ possesses asignificantly smaller ionic radius (65 pm in Oh and 49 pm inTd) than Fe2+ (78 pm in Oh and 63 pm in Td).In addition, a series of CoNiFe LDHTd/Ohsamples withdifferent Co, Ni, and Fe ratios were synthesized and character-ized by SEM. As presented in Fig. S4, the samples withCo : Ni : Fe ratios of 8 : 1 : 1, 7 : 2 : 1, 7 : 2 : 2, and 7 : 1 : 2 allretain well-defined and uniform nanocone structures. In con-trast, increasing the Fe proportion to a ratio of 6 : 1 : 3 led tothe collapse of the nanocone architecture, indicating thatexcessive Fe incorporation compromises structural stability.The corresponding elemental compositions determined byEDS are summarized in Table S2. Notably, the measured Fecontents are consistently lower than the nominal values,implying that Fe cannot be incorporated into the host layers infull stoichiometric proportions. This observation suggests thatonly a limited amount of Fe can be accommodated within theCoNi hydroxide lattice, likely due to disparities in ionic size orcoordination tendencies. The XRD patterns in Fig. S5 furtherconfirm that most of the CoNiFe LDHTd/Ohsamples retain thecharacteristic layered structure with an expanded interlayerspacing of approximately 2.5 nm, except for the Fe-rich samplewith a Co : Ni : Fe ratio of 6 : 1 : 3. For the Fe-rich composition,the disappearance of the 001 and 002 peaks indicates thereduction in long-range order along the c-axis, which mayresult from poor crystallinity or incomplete interlayer anionintercalation.Fig. 4a shows a SEM image of CoNiFe LDHTd/Oh, where thenanocone morphology is well preserved after oxidation, indi-cating the topotactic transformation process. The TEM image inFig. 4b further reveals that CoNiFe LDHTd/OhNCs possess a hollowinterior, with an average length of approximately 6 µm and a basediameter of around 1 µm. The HRTEM image in Fig. 4c displaysclearly resolved lattice fringes with an interlayer spacing of2.5 nm, which is consistent with the value obtained from theXRD analysis. The SAED pattern in Fig. 4d can be indexed to thein-plane ([001] zone-axis) diffraction of the hexagonal structurewith a lattice constant of a = 0.31 nm. In addition, based on theTG profile in Fig. S6 together with the corresponding EDS ana-lysis, the chemical composition of CoNiFe LDHTd/OhNCs with adesigned Co : Ni : Fe ratio of 3 : 1 : 1 is estimated to beCo0.68Ni0.23Fe0.09(OH)1.81DS0.19I0.09·0.95H2O.XPS was employed to investigate the electronic structurechanges induced by Fe incorporation into CoNi hydroxide. TheFig. 3 Schematic illustration of topochemical oxidation and exfoliation processes.Nanoscale PaperThis journal is © The Royal Society of Chemistry 2026 Nanoscale, 2026, 18, 13397–13408 | 13401XPS survey spectra in Fig. 4e confirm the presence of Co, Ni,Fe, and O in CoNiFe LDHTd/Oh. The high-resolution Co 2p andNi 2p spectra provide detailed insights into the oxidationstates and local electronic environments of metal centers. Asshown in Fig. 4f, the Co 2p peaks can be deconvoluted intocontributions from Co2+ and Co3+, accompanied by character-istic satellite features at higher binding energies. Similarly, theNi 2p spectra in Fig. 4g contain well-defined Ni2+ and Ni3+signals along with shake-up satellites. The Fe 2p spectrum,presented in Fig. 4h, displays a broad envelope comprising theFe 2p3/2 and Fe 2p1/2 components, overlapped with the CoLMM Auger signal and characteristic shake-up satellites.Despite this convolution, the distinct Fe3+ features remainclearly identifiable, confirming that Fe exists predominantly inthe trivalent state after oxidation. These confirm the coexis-tence of mixed-valence Co and Ni species in CoNi hydroxideand CoNiFe LDHTd/Oh. Notably, upon Fe incorporation, both Coand Ni peaks shift toward lower binding energies. Althoughthe shift direction is similar, the underlying electronicresponses are distinct. This behavior can be attributed tocharge redistribution within the LDHTd/Ohlayers induced byFe3+ incorporation, which is governed by the distinct coordi-nation environments of Co and Ni. Octahedrally coordinatedNi sites, with stronger metal–oxygen covalent bonding, tendtoward electron depletion, while Co sites with mixed tetra-hedral/octahedral coordination support electron accumu-lation. To maintain overall charge neutrality, a site-selectiveinternal electron rearrangement occurs through the M–O–Mnetwork, resulting in partial oxidation of Ni and reduction ofCo. This manifests as a coordination-dependent, cooperativeelectronic modulation within the multimetal framework. Theclear identification of Co2+/Co3+ and Ni2+/Ni3+ signaturesfurther confirms the successful integration of Fe into the hostlattice and its pronounced influence on the local electronicenvironment. On the other hand, diffuse UV-vis absorptionspectra were used to explore the coordination symmetry ofCoNiFe LDHTd/Oh. As shown in Fig. 4i, a broad absorption bandat around 500 nm is associated with Co species in Oh coordi-nation environments, whereas two pronounced bands near∼585 nm and ∼635 nm originate from the characteristic d–delectronic transitions of Co in Td sites.26,50 Compared withCoNi hydroxide, the Oh-related absorption band of CoNiFeLDHTd/Ohbecomes weaker, accompanied by a slight blue shiftof Td peaks, suggesting the coexistence of Oh and Td coordi-nation for Fe species.323.4. Exfoliation of LDH NCsCoNiFe LDHTd/OhNCs with interlayer DS− anions can bereadily delaminated into ultrathin NSs in formamide underultrasonication. As shown in Fig. 5, AFM images of Co8Ni1Fe1,Fig. 4 (a) SEM image, (b) TEM image, (c) HRTEM image, and (d) SAED pattern. XPS spectra of (e) survey scan, (f ) Co 2p, (g) Ni 2p, and (h) Fe 2p. (i)UV-vis spectra of CoNiFe LDHTd/Ohand CoNi hydroxide.Paper Nanoscale13402 | Nanoscale, 2026, 18, 13397–13408 This journal is © The Royal Society of Chemistry 2026Co7Ni2Fe1, Co7Ni2Fe2, Co3Ni1Fe1, and Co7Ni1Fe2 samplesdisplay well-dispersed, sheet-like objects with thicknessesaround 1 nm and lateral dimensions from tens to severalhundred nanometers. These features are consistent with pre-vious reports on monolayer LDH NSs.26 The measured thick-ness slightly exceeds the crystallographic thickness(∼0.48 nm), likely due to the peculiar Td/Oh coordination oradsorption of formamide and water molecules on thenanosheet surfaces.51,52 In contrast, due to an insufficient DS−intercalation, the Co6Ni1Fe3 sample could not be well exfo-liated, and no NSs are observed in Fig. 5f.Synchrotron in-plane diffractions of Co hydroxide, CoNihydroxide, and CoNiFe LDHTd/OhNSs are compared in Fig. 6a.The patterns can be indexed to the 10, 11, and 20 reflections,which are characteristic of the 2D hexagonal symmetry ofhydroxide NSs. These well-defined in-plane reflections confirmthe high crystallinity and well-preserved 2D lattice across allcompositions. Compared with Co hydroxide, CoNi hydroxideshows a shift toward in-plane lattice contraction. In addition,the reflections of CoNiFe LDHTd/Ohdisplay a further slight con-traction relative to those of its CoNi counterpart, which can beattributed to the successful oxidation of Fe2+ to Fe3+. Such sys-tematic peak shifts are fully consistent with the powder XRDresults, further substantiating the effective incorporation ofFe3+ and its influence on the local coordination environmentwithin the LDHTd/Ohstructure. In addition to the peak shifts,the gradual attenuation of the diffraction intensity is observedfrom Co hydroxide to CoNi hydroxide and CoNiFe LDH, imply-Fig. 6 (a) Synchrotron in-plane XRD patterns of Co hydroxide, CoNi hydroxide, and CoNiFe LDHTd/OhNSs. (b) PDF patterns of CoNiFe LDHTd/OhNCsand NSs.Fig. 5 AFM images of CoNiFe LDHTd/OhNSs with different metal ratios: (a) Co8Ni1Fe1, (b) Co7Ni2Fe1, (c) Co7Ni2Fe2, (d) Co3Ni1Fe1, (e) Co7Ni1Fe2, and(f ) Co6Ni1Fe3. The values represent the cross-sectional profile of the nanosheet.Nanoscale PaperThis journal is © The Royal Society of Chemistry 2026 Nanoscale, 2026, 18, 13397–13408 | 13403ing a reduction in in-plane crystallographic coherence. Thisbehavior is likely associated with lattice distortion andincreased structural disorder induced by heteroatom doping.To further elucidate the structural differences between CoNiFeLDHTd/OhNCs and their exfoliated nanosheet counterparts,PDF analysis was performed. As shown in Fig. 6b and Fig. S7,both samples display almost identical peak positions through-out the entire r range, indicating that the primary local coordi-nation environment around the metal sites is largely preservedafter exfoliation. In contrast, the exfoliated NSs exhibit signifi-cantly attenuated peak intensities, reflecting enhanced localdisorders typically associated with reduced dimensionality.49The attenuated peak intensities further suggest a reducedaverage coordination number, which can be attributed to boththe loss of interlayer stacking and the decreased lateral sizeupon exfoliation. Specifically, the disruption of interlayer cor-relations reduces atomic pair contributions along the out-of-plane direction, while the reduced nanosheet size increasesthe fraction of under-coordinated surface and edge sites,leading to the weakened PDF signals.3.5. Electrochemical performanceThe OER performance of CoNi hydroxide NCs with differentCo/Ni ratios was first examined. As shown in the LSV curves inFig. S8a, the introduction of an appropriate amount of Nimarkedly enhances the catalytic activity compared with thatwith pristine monometal (Co and Ni) hydroxides. The overpo-tentials at 10 mA cm−2 summarized in Fig. S8b furtherconfirm this trend. Among the catalysts, Co3Ni1 hydroxideachieves the lowest overpotential of 339 mV, outperforming Co(OH)2 (377 mV) and Ni(OH)2 (413 mV). These results indicatethat an optimized Co–Ni composition is essential for achievinghigh activity, while excessive Ni incorporation leads to reducedperformance. EIS measurements in Fig. S8c provide additionalinsight into the charge-transfer behavior. Co3Ni1 hydroxideshows the smallest Nyquist semicircle, corresponding to thelowest charge-transfer resistance (Rct). This observationdemonstrates that moderate Ni incorporation not onlyimproves the intrinsic catalytic characteristics but also facili-tates more effective interfacial charge transport. In contrast,Ni-rich samples and pure Ni(OH)2 present much larger semi-circles, indicating sluggish reaction kinetics and less favorableelectron-transfer behavior.The OER activities of CoNiFe LDHTd/OhNCs with variouselemental compositions were further systematically evaluated.As shown in the LSV curves in Fig. S9a, the Co3Ni1Fe1 LDHTd/Ohsample delivers markedly higher current densities at loweroverpotentials, indicating its superior catalytic performance.In contrast, compositions enriched in Co or Fe (e.g., Co8Ni1Fe1and Co6Ni1Fe3) exhibit noticeably inferior activity. As summar-ized in Fig. S9b, Co3Ni1Fe1 LDHTd/OhNCs achieve the lowestoverpotential of 280 mV at 10 mA cm−2, outperforming notonly the other ternary formulations but also their binarycounterparts, demonstrating the beneficial role of appropriateFe incorporation in boosting OER activity. The catalytic kine-tics were further assessed from the Tafel slopes in Fig. S9c.Co3Ni1Fe1 LDHTd/OhNCs exhibit the smallest slope (53.3 mVdec−1), which indicates more favorable reaction kinetics. Thisreduction in the Tafel slope correlates well with the lower over-potential, confirming that moderate Fe doping effectivelyaccelerates the OER process. Moreover, the Nyquist plots inFig. S9d show that Co3Ni1Fe1 LDHTd/OhNCs yield the smallestsemicircle radius, corresponding to the lowest Rct among thetested samples. This observation further underscores thekinetic advantages arising from the optimized Co–Ni–Fecomposition.The LSV curves in Fig. 7a clearly demonstrate that theternary CoNiFe LDHTd/OhNCs deliver the highest catalyticactivity, achieving markedly higher current densities at lowerapplied potentials. Both the binary CoNi hydroxide NCs andthe pristine Co hydroxide NCs exhibit inferior activity, whileRuO2 shows only moderate performance under identical con-ditions. These trends are quantified by the overpotentialsrequired to reach 10 mA cm−2 and plotted in Fig. 7b. CoNiFeLDHTd/OhNCs exhibit an overpotential of 280 mV, substantiallylower than those of CoNi hydroxide NCs (339 mV) and Cohydroxide NCs (377 mV). This comparison indicates that Niincorporation significantly enhances the intrinsic OER activityrelative to its Co counterpart, while Fe doping leads to anadditional and pronounced improvement in performance. TheTafel plots in Fig. 7c further confirm these findings. CoNiFeLDHTd/OhNCs show the smallest Tafel slope (53.3 mV dec−1),indicating the accelerated reaction kinetics of the ternary com-position. In contrast, CoNi hydroxide NCs and Co hydroxideNCs display notably larger Tafel slopes, reflecting slowerkinetic processes. The improved kinetics of CoNiFe LDHTd/OhNCs can be attributed to synergistic multimetal interactionsand the edge-rich surface of the nanocone morphology, whichmay facilitate the formation and deprotonation of OER inter-mediates. Consistent with the kinetic analysis, the Nyquistplots in Fig. 7d reveal that CoNiFe LDHTd/OhNCs possess thesmallest semicircle radius, corresponding to the lowest Rct.This further supports that introducing Fe enhances electrontransport and interface reaction rates. In comparison, Co andCoNi hydroxide NCs show larger Rct values. To gain insight intothe ECSA, the Cdl was estimated from CV measurements con-ducted at various scan rates within the non-faradaic region(Fig. S10). As depicted in Fig. 7e, CoNiFe LDHTd/OhNCs show thelargest Cdl (79.4 mF cm−2), markedly exceeding those of CoNihydroxide (43.0 mF cm−2) and Co hydroxide (18.4 mF cm−2).The results demonstrate that composition optimization playsdecisive roles in increasing the density of accessible active sites.To evaluate the long-term durability, the CoNiFe LDHTd/OhNCcatalyst was examined by chronopotentiometry testing at a con-stant current density of 10 mA cm−2 and the results are shownin Fig. 7f. The negligible potential fluctuation over 40 h demon-strates excellent operational stability under continuous OER con-ditions. In addition, the OER performance of CoNiFe LDHTd/Ohwas compared with recently reported non-precious metal elec-trocatalysts, as summarized in Table S3. The results demon-strate that CoNiFe LDHTd/Oh exhibits OER activity supassing thatof many recently reported catalysts.Paper Nanoscale13404 | Nanoscale, 2026, 18, 13397–13408 This journal is © The Royal Society of Chemistry 2026In contrast, Co3Ni1Fe1 LDH nanoplatelets with conventionalOh coordination were also prepared via the same topochemicaloxidation of CoNiFe brucite-type hydroxides using iodine. Asshown in Fig. S11, due to the relatively lower Fe3+ content, theresulting LDH nanoplatelets exhibit mixed-layer features withpartial DS− intercalation and the occurrence of the secondstaging phase.31,53,54 As revealed by the N2 adsorption–desorp-tion isotherms in Fig. S12, the LDHTd/OhNCs possess a notablylarger specific surface area (19.1 m2 g−1) than the nanoplate-lets (9.9 m2 g−1), indicating a higher electrochemically accessi-ble surface and a greater density of exposed active sites.Consistent with this structural advantage, the NCs exhibit alower overpotential, faster reaction kinetics, and improvedcharge-transfer behavior compared with the nanoplatelets, asevidenced by the LSV, Tafel, and impedance analyses inFig. S13. In addition, the larger ECSA of the NCs suggestsmore accessible active sites. The superior performance ofLDHTd/OhNCs can be attributed to the synergistic effects of thehollow nanocone morphology and the coexistence of Td/Ohcoordination environments, which together facilitate masstransport, enhance electronic conductivity, and optimize theintrinsic activity of the catalytic sites relative to conventionalOh coordinated nanoplatelets.The OER electrocatalytic activity of the exfoliated CoNiFeLDHTd/OhNSs was also evaluated and compared with that oftheir nanocone counterparts under alkaline conditions. Tofacilitate the practical handling and utilization of the CoNiFeLDHTd/OhNSs, they were flocculated using carbonate (CO32−)anions. The SEM image in Fig. 8a reveals that the flocculatedproduct exhibits a loose, fluffy-like morphology composed ofinterconnected NSs. Such a porous architecture is expected toenhance the accessible specific surface area, thereby facilitat-ing subsequent processing and application. As shown in theXRD pattern of the flocculated product in Fig. 8b, a series ofintense 00l reflections previously observed for the NCs disap-pear, indicating the disruption of long-range stacking orderalong the c-axis after exfoliation. Meanwhile, the d-spacing ofthe restacked NSs is determined to be 0.79 nm, which is con-sistent with CO32− intercalation within the interlayer galleries.Notably, the N2 adsorption–desorption isotherms in Fig. 8cdemonstrate that CoNiFe LDHTd/OhNSs display a significantlyhigher adsorption capacity, corresponding to a much largerspecific surface area of 71.8 m2 g−1 compared with 19.1 m2 g−1for the NCs. This increase originates from the reduced lateraland stacking dimensions after exfoliation, leading to lessordered aggregation and more exposed surfaces. As a result,the flocculated nanosheet architecture forms a more openporous network, facilitating mass transport and thereby pro-viding a structural basis for enhanced electrocatalytic perform-ance. However, it should be noted that the restacked NSsexhibit relatively small interlayer spacing (∼0.79 nm), whichmay make the interlayer less accessible to the electrolyte. Incontrast, the NCs possess a larger interlayer spacing(∼2.5 nm), which facilitates ion transport and improves theutilization of internal surfaces. As evidenced by the LSV curvesin Fig. 8d, LDHTd/OhNSs exhibit a significantly reduced overpo-tential of 267 mV at a current density of 10 mA cm−2, which ismarkedly lower than that of the NCs, indicating substantiallyenhanced OER performance. According to the results inFig. 8e, CoNiFe LDHTd/OhNSs deliver a larger Cdl value(96.8 mF cm−2) than CoNiFe LDHTd/OhNCs (79.4 mF cm−2),implying a higher ECSA. The smaller increase in Cdl relative toFig. 7 Comparison of OER performance. (a) LSV curves, (b) overpotentials at 10 mA cm−2, (c) Tafel slopes, (d) Nyquist plots, (e) current densitydifferences versus scan rates measured in the non-faradaic ranges of CoNiFe LDHTd/OhNCs, CoNi hydroxide NCs, Co hydroxide NCs, and commercialRuO2. (f ) Chronopotentiometry test of CoNiFe LDHTd/OhNCs.Nanoscale PaperThis journal is © The Royal Society of Chemistry 2026 Nanoscale, 2026, 18, 13397–13408 | 13405the BET surface area reflects a trade-off between enhancedsurface area and reduced electrochemical accessibility associ-ated with the decreased interlayer spacing. Despite this limit-ation, the ultrathin NS structure still exposes more active sitesto the electrolyte, resulting in an overall increase in ECSA andthe observed performance enhancement. To decouple the con-tributions from active site density and intrinsic activity, thecurrent densities were normalized by ECSA, as shown inFig. S14. After normalization, CoNiFe LDHTd/OhNSs exhibitslightly higher current density than NCs, suggesting that theperformance enhancement is dominated by increased activesite density, accompanied by a modest improvement in intrin-sic activity due to structural and electronic modulation uponexfoliation. EIS was employed to investigate the charge-transferproperties of the catalysts. As illustrated in the Nyquist plots inFig. 8f, the NSs display a smaller semicircle diameter than theNCs, corresponding to a reduced Rct. The accelerated inter-facial electron transport facilitates the adsorption and conver-sion of OER intermediates, thereby further promoting the reac-tion kinetics. Overall, the superior OER performance of theLDHTd/OhNSs can be ascribed to the synergistic effects ofenlarged ECSA and enhanced charge-transfer kinetics inducedby the exfoliated nanosheet architecture.4. ConclusionsBinary CoNi and ternary CoNiFe hydroxide NCs with mixedTd/Oh coordination were successfully constructed via controlledNi and Fe incorporation into Co-based hydroxide NCs, demon-strating an effective strategy for enhancing electrocatalyticactivity through multimetal synergy. Systematic compositionaltuning of CoNi hydroxide NCs revealed that moderate Ni incor-poration optimizes OER performance, with the Co3Ni1 sampledelivering a small overpotential of 339 mV at 10 mA cm−2.Subsequent Fe incorporation followed by a topochemical oxi-dative intercalation process yielded ternary CoNiFe LDHTd/Oh.Among the ternary systems, the NCs with a Co3Ni1Fe1 compo-sition exhibited the most favorable electrocatalytic perform-ance, achieving the lowest overpotential of 280 mV at 10 mAcm−2, highlighting the critical role of Fe doping. Furthermore,the ternary LDHTd/OhNCs were readily exfoliated into mono-layer NSs with atomic-scale thickness. Owing to the enlargedspecific surface area and increased exposure of active sites, theNSs displayed further enhanced OER performance relative tothe NCs, with the overpotential further reduced to 267 mV.Overall, this work underscores the synergistic effects of compo-sitional modulation, coordination engineering, and morpho-logical design in advancing high-performance layered hydrox-ide electrocatalysts.Author contributionsZ. Zhang: conceptualization, investigation, methodology, datacuration, formal analysis, and writing – original draft. X. Jiang:data analysis, validation, and writing – review & editing. N. Ma:investigation, formal analysis, and writing – review & editing.J. Zhang: formal analysis and writing – review & editing.E. Picheau: investigation and writing – review & editing. N.Sakai: investigation and writing – review & editing. T. Sasaki:supervision and writing – review & editing. R. Ma: conceptual-ization, funding acquisition, supervision, and writing – review& editing.Fig. 8 (a) SEM image and (b) XRD pattern of flocculated NSs. (c) N2 adsorption–desorption isotherms. (d) LSV curves, (e) current density differencesversus scan rates measured in the non-faradaic range, and (f ) Nyquist plots.Paper Nanoscale13406 | Nanoscale, 2026, 18, 13397–13408 This journal is © The Royal Society of Chemistry 2026Conflicts of interestThere are no conflicts to declare.Data availabilityThe data supporting this article have been included as part ofthe supplementary information (SI). Supplementary infor-mation: SEM, XRD, TG, PDF, and electrochemical measure-ments, and BET data. See DOI: https://doi.org/10.1039/d6nr00271d.AcknowledgementsThis work was supported in part by the World PremierInternational Research Center Initiative (WPI), Ministry ofEducation, Culture, Sports, Science and Technology (MEXT),Japan. R. M. acknowledges support from JSPS KAKENNHI(22H01916, 22K18956, 25K22208 and 26H02227). J. Z. acknowl-edges JSPS International Research Fellows (24KF0273). The in-plane XRD measurements were performed under the approvalof the Photon Factory Program Advisory Committee (ProposalNo. 2024G501). The XPS facility at NIMS Materials AnalysisStation is gratefully acknowledged. We acknowledge BL04B2beamlines at SPring-8 for the synchrotron X-ray total scatteringexperiments with the approval of JASRI (Proposal No.2025A1067 and 2025B1248). A part of this work was supportedby the Electron Microscopy Unit, National Institute forMaterials Science (NIMS).References1 Z. W. Seh, J. Kibsgaard, C. F. Dickens, I. Chorkendorff,J. K. Nørskov and T. F. Jaramillo, Science, 2017, 355,eaad4998.2 J. Lai, B. Huang, Y. Chao, X. Chen and S. Guo, Adv. Mater.,2019, 31, 1805541.3 Y. Jiao, Y. Zheng, M. Jaroniec and S. Z. Qiao, Chem. Soc.Rev., 2015, 44, 2060–2086.4 J. Song, C. Wei, Z.-F. Huang, C. Liu, L. Zeng, X. Wang andZ. J. Xu, Chem. Soc. Rev., 2020, 49, 2196–2214.5 B. You, M. T. Tang, C. Tsai, F. Abild-Pedersen, X. Zhengand H. Li, Adv. Mater., 2019, 31, 1807001.6 J. Zhang, Z. Zhang, R. Ma and T. Sasaki, ACS Energy Lett.,2026, 11, 101–110.7 H. Sun, X. Xu, Z. Hu, L. H. Tjeng, J. Zhao, Q. Zhang,H.-J. Lin, C.-T. Chen, T.-S. Chan, W. Zhou and Z. Shao,J. Mater. Chem. A, 2019, 7, 9924–9932.8 M. Tahir, L. Pan, F. Idrees, X. Zhang, L. Wang, J.-J. Zou andZ. L. Wang, Nano Energy, 2017, 37, 136–157.9 J. Yang, J. K. Cooper, F. M. Toma, K. A. Walczak, M. Favaro,J. W. Beeman, L. H. Hess, C. Wang, C. Zhu, S. Gul, J. Yano,C. Kisielowski, A. Schwartzberg and I. D. Sharp, Nat.Mater., 2017, 16, 335–341.10 K. A. Stoerzinger, L. Qiao, M. D. Biegalski and Y. Shao-Horn, J. Phys. Chem. Lett., 2014, 5, 1636–1641.11 T. Audichon, T. W. Napporn, C. Canaff, C. Morais,C. Comminges and K. B. Kokoh, J. Phys. Chem. C, 2016,120, 2562–2573.12 H. Over, ACS Catal., 2021, 11, 8848–8871.13 M. Gong and H. Dai, Nano Res., 2015, 8, 23–39.14 M. S. Burke, L. J. Enman, A. S. Batchellor, S. Zou andS. W. Boettcher, Chem. Mater., 2015, 27, 7549–7558.15 K. Zhang and R. Zou, Small, 2021, 17, 2100129.16 H. Sun, Z. Yan, F. Liu, W. Xu, F. Cheng and J. Chen, Adv.Mater., 2020, 32, 1806326.17 Z. Li, D. Liao, G. Tian, X. Fan, X. Chai, W. Chang, Y. Gao,B. Yuan, Z. Li, F. Wei and C. Zhang, J. Am. Chem. Soc.,2025, 147, 32548–32559.18 M. Xu and M. Wei, Adv. Funct. Mater., 2018, 28, 1802943.19 Y. Wang, M. Zhang, Y. Liu, Z. Zheng, B. Liu, M. Chen,G. Guan and K. Yan, Adv. Sci., 2023, 10, 2207519.20 G. Chen, H. Wan, W. Ma, N. Zhang, Y. Cao, X. Liu, J. Wangand R. Ma, Adv. Energy Mater., 2020, 10, 1902535.21 L. Tian, K. Wang, H. Wo, Z. Li, M. Song, J. Li, T. Li andX. Du, J. Taiwan Inst. Chem. Eng., 2019, 96, 273–280.22 Z. Li, D. Liu, X. Lu, M. Du, Z. Chen, J. Teng, R. Sha andL. Tian, Dalton Trans., 2022, 51, 1527–1532.23 S. Tang, Y. Zhou, X. Lu, Z. Chen, Z. Huang, Z. Li andL. Tian, J. Alloys Compd., 2022, 924, 166415.24 X. Feng, Q. Jiao, W. Chen, Y. Dang, Z. Dai, S. L. Suib,J. Zhang, Y. Zhao, H. Li and C. Feng, Appl. Catal., B, 2021,286, 119869.25 Z. Zhang, R. Zhang, N. Ma, E. Picheau, L. K. Shrestha,W. Zhou, X. Liu, Y. Sugahara, T. Sasaki and R. Ma, Small,2025, 21, 2502344.26 X. Liu, R. Ma, Y. Bando and T. Sasaki, Angew. Chem., Int.Ed., 2010, 49, 8253–8256.27 X. Liu, R. Ma, Y. Bando and T. Sasaki, Adv. Mater., 2012, 24,2148–2153.28 X. Liu, R. Ma, Y. Bando and T. Sasaki, Adv. Funct. Mater.,2014, 24, 4292–4302.29 L. Jia, H. Wan, X. Liu, G. Chen, N. Zhang, J. Li, W. Zhou,Y. Cao, R. Ma and G. Qiu, ChemSusChem, 2019, 12, 5274–5281.30 R. Ma, Z. Liu, K. Takada, N. Iyi, Y. Bando and T. Sasaki,J. Am. Chem. Soc., 2007, 129, 5257–5263.31 R. Ma, J. Liang, K. Takada and T. Sasaki, J. Am. Chem. Soc.,2011, 133, 613–620.32 Y. He, X. Liu, G. Chen, J. Pan, A. Yan, A. Li, X. Lu, D. Tang,N. Zhang, T. Qiu, R. Ma and T. Sasaki, Chem. Mater., 2020,32, 4232–4240.33 A. Karmakar, K. Karthick, S. S. Sankar, S. Kumaravel,R. Madhu and S. Kundu, J. Mater. Chem. A, 2021, 9, 1314–1352.34 J. Wang and H. C. Zeng, ACS Appl. Energy Mater., 2018, 1,4998–5007.35 Z. Zhang, Z. Zheng, N. Ma, E. Picheau, N. Sakai,Y. Sugahara, T. Sasaki and R. Ma, Chem. Eng. J., 2025, 509,161248.Nanoscale PaperThis journal is © The Royal Society of Chemistry 2026 Nanoscale, 2026, 18, 13397–13408 | 13407https://doi.org/10.1039/d6nr00271dhttps://doi.org/10.1039/d6nr00271dhttps://doi.org/10.1039/d6nr00271d36 Y. Lin, H. Wang, C.-K. Peng, L. Bu, C.-L. Chiang, K. Tian,Y. Zhao, J. Zhao, Y.-G. Lin, J.-M. Lee and L. Gao, Small,2020, 16, 2002426.37 J. Saha and F. A. Molla, Nanoscale, 2025, 17, 26050–26056.38 M.-Y. Xie, J.-R. Huang, H. Wan, J. Nie, M.-H. Xian, Z.-Y. Ou-Yang, G.-F. Huang and W.-Q. Huang, Appl. Phys. Lett., 2025,126, 153901.39 J. Nie, J. Shi, L. Li, M.-Y. Xie, Z.-Y. Ouyang, M.-H. Xian,G.-F. Huang, H. Wan, W. Hu and W.-Q. Huang, Adv. Funct.Mater., 2025, 35, 2414493.40 J.-R. Huang, M.-Y. Xie, M.-H. Xian, Y. Luo, J.-H. Nie,Z.-Y. Ou-Yang, Q.-X. Wang, G.-F. Huang and W.-Q. Huang,Appl. Phys. Lett., 2025, 127, 103905.41 S. Anantharaj, S. Kundu and S. Noda, Nano Energy, 2021,80, 105514.42 J. Wei, J. Zhu, R. Jin, Y. Liu, G. Liu, M.-H. Fan, M. Liu,D. Jiang and J. Zeng, J. Am. Chem. Soc., 2025, 147, 13502–13511.43 L. Trotochaud, S. L. Young, J. K. Ranney andS. W. Boettcher, J. Am. Chem. Soc., 2014, 136, 6744–6753.44 R. Ma, J. Liang, X. Liu and T. Sasaki, J. Am. Chem. Soc.,2012, 134, 19915–19921.45 S. Niu, W.-J. Jiang, T. Tang, L.-P. Yuan, H. Luo and J.-S. Hu,Adv. Funct. Mater., 2019, 29, 1902180.46 C. C. L. McCrory, S. Jung, J. C. Peters and T. F. Jaramillo,J. Am. Chem. Soc., 2013, 135, 16977–16987.47 M. W. Terban and S. J. L. Billinge, Chem. Rev., 2022, 122,1208–1272.48 S. J. L. Billinge and M. G. Kanatzidis, Chem. Commun.,2004, 749–760.49 D. A. Keen and A. L. Goodwin, Nature, 2015, 521, 303–309.50 R. Ma, Z. Liu, K. Takada, K. Fukuda, Y. Ebina, Y. Bandoand T. Sasaki, Inorg. Chem., 2006, 45, 3964–3969.51 W. Ma, R. Ma, C. Wang, J. Liang, X. Liu, K. Zhou andT. Sasaki, ACS Nano, 2015, 9, 1977–1984.52 R. Ma and T. Sasaki, Adv. Mater., 2010, 22, 5082–5104.53 N. Iyi, K. Kurashima and T. Fujita, Chem. Mater., 2002, 14,583–589.54 N. Iyi, K. Fujii, K. Okamoto and T. Sasaki, Appl. Clay Sci.,2007, 35, 218–227.Paper Nanoscale13408 | Nanoscale, 2026, 18, 13397–13408 This journal is © The Royal Society of Chemistry 2026 Button 1: