Abundant Active Edge Research Articles

Phase engineering and N doping modulated MoSe2 nanosheets for large-current–density hydrogen evolution in simulated seawater

Molybdenum selenide (MoSe2) is considered to be a promising catalyst for seawater hydrogen evolution, but its catalytic activity falls far short of requirements due to its inert surface. Here, self-supported N-doped 1T@2H-MoSe2/N doped carbon paper (N-MoSe2/NCP) was fabricated by a novel low-temperature nitrogen plasma strategy. In alkaline simulated seawater, the optimized N-MoSe2/NCP-30 only requires an overpotential of 274 mV to reach −200 mA cm−2 with Tafel slope of 54.7 mV dec-1, and exhibits stability over 24 h. This work proposes that the introduction of 1 T phase and N dopant into 2H-MoSe2 using low-temperature plasma strategy can significantly facilitate the exposure of abundant active edge sites and boost the conductivity of MoSe2.

Synthesis of Cu2-xSe-MoSe2 Edge-Epitaxial Heterostructure for Efficient Electrocatalytic Hydrogen Evolution.

The exposure of active edge sites of transition metal dichalcogenide (TMD) in TMD-based heterostructures is essential to enhance the catalytic activity toward electrochemical catalytic hydrogen evolution (HER). The construction of TMD-based edge-epitaxial heterostructures can maximally expose the active edge sites. However, owing to the 2D crystal structures, it remains a great challenge to vertically align layered TMDs on non-layered metal chalcogenides. Herein, the synthesis of Cu2-xSe-MoSe2 edge-epitaxial heterostructure is reported by a facile one-pot wet-chemical method. A high density of MoSe2 nanosheets grown vertically to the <111>Cu2-xSe on the surface of Cu2-xSe nanocrystals is observed. Such edge-epitaxial configuration allows the exposure of abundant active edge sites of MoSe2 and enhances the changer transfer between MoSe2 and Cu2-xSe. As a result, the obtained Cu2-xSe-MoSe2 epitaxial heterostructures show excellent HER performance as compared to that of Cu2-xSe@1T/2H-MoSe2 core@shell heterostructure with similar size. This work not only offers a novel approach for designing efficient electrochemical catalysis but also enriches the diversity of TMD-based heterostructures, holding promise for various applications in the future.

Synergism of Edge Effect and Interlayer Engineering of VS2 on CNFs for Rapid and Precise NO2 Detection.

Although two-dimensional (2D) transition-metal dichalcogenides (TMDs) exhibit attractive prospects for gas-sensing applications, the rapid and precise sensing of TMDs at low loss remains challenging. Herein, a NO2 sensor based on an expanded VS2 (VS2-E)/carbon nanofibers (CNFs) composite (abbreviated as VS2-E-C) with ultrafast response/recovery at a low-loss state is reported. In particular, the impact of the CNF content on the NO2-sensing performance of VS2-E-C was thoroughly explored. Expanded VS2 nanosheets were grafted onto the surface of hollow CNFs, and the combination boosted the charge transport, exposing abundant active edges of VS2, which enhanced the adsorption of NO2 efficiently. The activity of the VS2 edge is further confirmed by stronger NO2 adsorption with a more negative adsorption energy (-3.42 eV) and greater than the basal VS2 surface (-1.26 eV). Moreover, the exposure of rich edges induced the emergence of the expanded interlayers, which promoted the adsorption/desorption of NO2 and the interaction of gas molecules within VS2-E-C. The synergism of edge effect and interlayer engineering confers the VS2-E-C3 sensor with ultrafast response/recovery speed (9/10 s) at 60 °C, high sensitivity (∼2.50 to 15 ppm NO2), good selectivity/stability, and a low detection limit of 23 ppb. The excellent "4S" functions indicate the promising prospect of the VS2-E-C3 sensor for fast and precise NO2 detection at low-loss condition.

Manipulating polysulfide catalytic conversion through edge site construction, hybrid phase engineering, and Se anion substitution for kinetics-enhanced lithium-sulfur battery

Applying catalytic materials in Li-S batteries can effectively enhance the lithium polysulfides (LiPSs) conversion kinetics and suppress the severe LiPSs shuttle effect. However, optimizing the catalytic activity of catalysts through synchronous geometrical/electronic structure design remains challenging. Here, we demonstrate that the highly stable MoSSe@graphene (MoSSe@rGO) electrocatalyst, with vertically aligned geometry configuration, 1T/2H hybrid phase engineering, and Se anion substitution, can effectively trap and catalyze the LiPSs conversion. The vertically grown MoSSe nanosheets on rGO expose abundant active edge sites and ensure that every MoSSe nanosheet participates in chemical adsorption and catalytic reaction. The 1T/2H hybrid phase possesses high electronic conductivity, enabling direct and fast adsorption/catalyzing of LiPSs. Moreover, the Se anion substitution in 1T/2H-MoS2 enhances the Li+ diffusion kinetics and accelerates the LiPSs redox reaction. Due to the synergy of geometrical (edge sites) and electronic (1T/2H phase and Se substitution) engineering, the 1T/2H-MoSSe@rGO affords strong chemical adsorption and enhanced bidirectional catalytic activity toward LiPSs, endowing the Li-S batteries with ultra-small voltage hysteresis (125 mV at 0.2 C), ultrahigh rate capability (747.2 mAh g−1 at 3 C), and long cycle life over 500 cycles. Further, theoretical simulation and ex-situ measurements verify the catalysis mechanism of 1T/2H-MoSSe@rGO and demonstrate its ultra-stable operation upon cycling. This work provides a geometrical/electronic multi-construction strategy to design superior Li-S catalysts.

Enhanced non-layer-dependent piezo-response in sailboat-like vertical molybdenum disulfide nanosheets for piezo-catalytic hydrogen evolution and dye degradation: Effect of microstructure and phase composition

The piezo-response of two-dimensional molybdenum disulfide(MoS2) only exists at the edge of odd-number layers. It’s crucial to design reasonable micro/nano-structures and construct tight interfaces to weaken layer-dependence, enhance energy harvesting, charge transfer and active sites exposure to improve piezoelectricity. The novel sailboat-like-vertical-MoS2-nanosheets(SVMS), in which abundant vertical MoS2 nanosheets(∼20 nm, 1–5 layers) are uniformly distributed on horizontal substrate of MoS2, with abundant vertical interfaces and controllable phase composition are prepared by facile method. The larger geometric-asymmetry enhances mechanical energy capture. Experiment and theory revealed the enhanced in-/out-of-plane polarization, higher piezo-response in multi-directions and abundant active edge sites of SVMS, thereby eliminating the layer-dependence and generating higher piezo-potential. Cooperating with the Mo-S bonds at vertical interfaces, free electrons-holes are efficiently separated and migrated. The piezo-degradation of Rhodamine B(RhB) and hydrogen evolution rate under ultrasonic/stirring are 0.16 min−1 and 1598 μmolg−1h−1 for SVMS(2H) with the highest piezo-response (under ultrasonic wave, stirring and water flow), which are over 1.6 and 3.1 times than few-layer MoS2 nanosheets. 94% RhB(500 mL) is degraded under water-flow(60 min). The mechanism was proposed. Overall, the design of SVMS with enhanced piezoelectricity was studied and modulated by regulating microstructure and phase composition, which has excellent application potential in fields of environment, energy and novel materials.

An ultrasensitive FET biosensor based on vertically aligned MoS2 nanolayers with abundant surface active sites

Molybdenum disulfide (MoS2) nanolayers are one of the most promising two-dimensional (2D) nanomaterials for constructing next-generation field-effect transistor (FET) biosensors. In this article, we report an ultrasensitive FET biosensor that integrates a novel format of 2D MoS2, vertically-aligned MoS2 nanolayers (VAMNs), as the channel material for label-free detection of the prostate-specific antigen (PSA). The developed VAMNs-based FET biosensor shows two distinctive advantages. First, the VAMNs can be facilely grown using the conventional chemical vapor deposition (CVD) method, permitting easy fabrication and potential mass device production. Second, the unique advantage of the VAMNs for biosensor development lies in its abundant surface-exposed active edge sites that possess a high binding affinity with thiol-based linkers, which overcomes the challenge of molecule functionalization on the conventional planar MoS2 nanolayers. The high binding affinity between 11-mercaptoundecanoic acid and the VAMNs was demonstrated through experimental surface characterization and theoretical calculations via density functional theory. The FET biosensor allows rapid (within 20 min) and ultrasensitive PSA detection in human serum with simple operations (limit of detection: 800 fg mL−1). This FET biosensor offers excellent features such as ultrahigh sensitivity, ease of fabrication, and short assay time, and thereby possesses significant potential for early-stage diagnosis of life-threatening diseases.

Multifunctional Template Prepares N-, O-, and S-Codoped Mesoporous 3D Hollow Nanocage Biochar with a Multilayer Wall Structure for Aqueous High-Performance Supercapacitors

To recycle wastes and develop renewable energy, much effort has been focused on converting biowastes into porous carbon for supercapacitors. Porous nanocage-like carbons have excellent capacitive properties, but generally their preparation methods are costly or complex. Herein, a “one-step” strategy of synchronous activation and support through the thermal decomposition of a multifunctional template (magnesium acetate, Mg(Ac)2) is designed to prepare N-, O-, and S-codoped mesoporous hollow biochar nanocages (BNC-700). The BNC-700 prepared displays an interconnected porous structure and a two-dimensional (2D) multilayer wall/three-dimensional (3D) hollow nanocage structure with abundant active heteroatoms and edge defects. Due to their specific structures, high surface areas (1369 m2 g–1), and large pore volumes (1.81 cm3 g–1), the assembled supercapacitor delivers a considerable energy density of 37.4 Wh kg–1 at 212 W kg–1 and cycling stability of 99.5% after 15,000 cycles. The unique structure and N, O, and S codoping characteristics ensure a potential application for BNC-700 in supercapacitors. In summary, a strategy is designed for the green, simple, and cost-effective preparation of high-performance biochar for advanced energy storage devices.

O-doping induced abundant active-sites in MoS2 nanosheets for propelling polysulfide conversion of Li-S batteries

The oxygen doped MoS2 nanosheets were in-situ grown into the three-dimensional (3D) porous graphene frameworks (O-MoS2/G) through a facile hydrothermal method, and then used to coat the commercial PP separators for Li-S batteries. The relatively low hydrothermal temperature should be a key factor for achieving the O-doped MoS2. The O dopants could expand and disturb interlayer structures of MoS2 to produce abundant active edge sites for adsorption and catalytic conversion of polysulfides. Moreover, the basal planes of MoS2 should be also activated by the O doping and exhibit enhanced chemical adsorption strength towards polysulfides for propelling electrochemical conversion. Owing to the synergistic effects of the 3D porous graphene frameworks and the inlaid O-MoS2 nanosheets, the Li-S cells with high S areal loading cathodes and O-MoS2/G@PP separators exhibit excellent electrochemical performances with a high specific capacity of 1141 mAh g−1 at the 1st cycle at 0.1 C, reversible capacities of 772 mAh g−1 at the 50th cycle at 0.2 C and 583 mAh g−1 at the 100th cycle at 0.5 C. These encouraging results provide that the heteroatom doping should be a promising approach to improve the adsorption and catalytic activity of MoS2 for propelling the polysulfide conversion in Li-S batteries.

Engineering low platinum loaded defects enriched PtxCo wrapped by carbon layers for efficient methanol electrooxidation with CO-free dominant

Constructing robust nanomaterials with surface defects is a promise way for high-efficiency methanol electrocatalysis together with minimizing poisoning of adsorbed CO. To this end, low platinum (Pt) loaded (6% wt) defects enriched PtCo alloy wrapped by carbon layers (V-PtxCo@NC/C) enabled via facile pyrolysis. In the pyrolysis process, the metal salts are subjected to alloying and dealloying process under high temperature annealing combined with etching treatment to construct defects and boundaries enriched PtCo alloy. These defects and boundaries enriched structure can provide abundant active edge atoms with low coordination numbers as well as are beneficial for more exposed active sites of Pt, rendering the large electrochemical surface areas and changing the reaction properties for intermediates of methanol oxidation. In-situ Fourier transform infrared spectroscopy shows that the catalyst follows direct HCOO− pathway with CO-free dominant. Thus, presenting excellent mass activity (1328 mA mg−1Pt) in acid medium. Moreover, benefiting from the protection of carbon layers, possible dissolution of metallic can be diminished. Therefore, the catalyst delivers superhigh stability and can maintain 80% of mass activity after 1000 cycles. This work poses a new avenue for the design of cost-effective catalyst.

Design of XS2 (X=W or Mo)-Decorated VS2 Hybrid Nano-Architectures with Abundant Active Edge Sites for High-Rate Asymmetric Supercapacitors and Hydrogen Evolution Reactions.

Two-dimensional layered transition metal dichalcogenides have emerged as promising materials for supercapacitors and hydrogen evolution reaction (HER) applications. Herein, the molybdenum sulfide (MoS2 )@vanadium sulfide (VS2 ) and tungsten sulfide (WS2 )@VS2 hybrid nano-architectures prepared via a facile one-step hydrothermal approach is reported.Hierarchical hybrids lead to rich exposed active edge sites, tuned porous nanopetals-decorated morphologies, and high intrinsic activity owing to the strong interfacial interaction between the two materials. Fabricated supercapacitors using MoS2 @VS2 and WS2 @VS2 electrodes exhibit high specific capacitances of 513and 615F g- 1 , respectively, at an applied current of 2.5A g- 1 by the three-electrode configuration. The asymmetric device fabricated using WS2 @VS2 electrode exhibits a high specific capacitance of 222F g- 1 at an applied current of 2.5A g- 1 with the specific energy of 52Wh kg- 1 at a specific power of 1kW kg- 1 . For HER, the WS2 @VS2 catalyst shows noble characteristics with an overpotential of 56mV to yield 10mA cm- 2 , a Tafel slope of 39mV dec-1 , and an exchange current density of 1.73mA cm- 2 . In addition, density functional theory calculations are used to evaluate the durable heterostructure formation and adsorption of hydrogen atom on the various accessible sites of MoS2 @VS2 and WS2 @VS2 heterostructures.

Ligand-confined bismuth based nanodots for robust carbon dioxide reduction to liquid fuel at 1 A/cm2

The bismuth oxide (BiOx) derived electrocatalysts hold the promise for effective carbon dioxide (CO2) reduction to formate as liquid fuel. However, the disappearance of the active edge sites during the electroreduction, due to the spontaneous aggregation of nanoclusters into large sheets, lowers the performance at high current densities. Here we develop a ligand-confined strategy to stabilize Bi-BiOx nanodots with a diameter of ca. 5 nm, enabling efficient CO2 reduction to formate with high activity (working current density up to 1 A/cm2) and high selectivity (Faradaic efficiency of >95 %). We find that the poly(methacrylic acid) ligand would in-situ transform into carbon shell as a confinement area that limits the growth of Bi-BiOx nanodots, thus keeping the abundant active edge sites for CO2 reduction at wide working potentials. We also note that the carboxyl group in ligand remained on nanodots may provide oxygen donors for Bi-BiOx to maintain the selective formate generation at high current densities.

Efficient Lithium/Sodium-Ion Storage by Core-Shell Carbon Nanospheres@TiO2 Decorate by Epitaxial WSe2 Nanosheets Derived from Bimetallic Polydopamine Composites.

Metal-polydopamine coordination chemistry attracts great attention owing to the synergistic effect of adjustable components and advantageous structures. However, few efforts have been devoted to exploring bimetal-polydopamine composites, especially for multistructural composites with high-capacity components and high stability. In this regard, the TiO2 @C-WSe2 core-shell nanospheres are designed and fabricated based on Ti-W-polydopamine composites after selenization, in which the TiO2 nanoparticles are encapsulated or embedded in the carbon nanospheres and the external WSe2 nanosheets are grown epitaxially on the carbon surfaces, featuring multiple channels for ion diffusion and abundant active edges for electrochemical reactions. The introduction of WSe2 not only greatly improves the capacity but also results in exponential growth of the active edge. As a result, the as-prepared TiO2 @C-WSe2 displayed long-term cycling performance in lithium-ion batteries. Furthermore, the anode is assembled into sodium-ion batteries, manifesting a stable capacity of 352mA h g-1 at 1.0 A g-1 even after 2000 cycles, one of the best performances for polydopamine-based composites. Enhanced performance can be attributed to the synergies of high-capacity components and different dimensional materials. This work highlights that the rational design of functional structures provides a novel inspiration for electrodes with effective nanoarchitectures.

Ceria and gold co-decorated porous MoS2@graphene nanocomposite electrochemical electrode integrated with smartphone-controlled microstation for simultaneous dual metal ions detection

Continuous increase in release of toxic metals into ecosystem posed a threat to public ecology, leading to demand for the portable monitoring system to control contamination source and monitor disease progression. Herein, ceria and gold co-decorated porous MoS2@graphene nanocomposite was synthesized to construct electrochemical chip and integrate with smartphone-controlled hand-held microstation for simultaneous detecting Zn(II) and Cu(II). Concretely, MoS2 nanosheets coated polyimide were firstly laser-induced into 3D frame-structured MoS2/graphene with abundant oxygen-containing groups and active breaking edges, thereby accelerating the electron transfer and improving the absorptivity and reductive affinity for divalent ions. Double electro-deposition of ceria and gold provide vast oxygen vacancies for sensing, and Ce(III)/Ce(IV) cycle inhibit the recombination of electrons and holes, prolonging the life of carriers to enhance its electro-conductibility. The hydroxylation of ceria under acidic conditions is favorable for ions adsorption. Benefitting from synergetic effect among materials, the smartphone-controlled sensing system exhibits high sensitivity and low detection limit for Cu(II) of 2.8 ppt and Zn(II) of 103.6 ppt. Low energy barrier of target plating/stripping kinetics were also substantiated via calculating activation energy upon composite using Arrhenius formula. Furthermore, its outstanding flexibility, reusability, and anti-interference performance was verified, indicating the potential implementation possibilities in complex environment.

In-situ growth of hierarchical trifunctional Co4S3/Ni3S2@MoS2 core-shell nanosheet array on nickel foam for overall water splitting and supercapacitor

It is an enormous challenge to construct the cheap and effective multifunctional electrocatalysts for energy storage and conversion applications. Herein, a ZIF-67 derived Co4S3/Ni3S2@MoS2 core-shell nanosheet arrays were successfully developed on nickel foam via a simple two-step hydrothermal vulcanization method for electrocatalytic water splitting and supercapacitors. For overall water splitting, CNM 0.5 required the overpotentials of 96 and 269 mV at 10 mA cm−2 and 100 mA cm−2 for HER and OER in 1 M KOH. The dual-electrode electrolytic cell assembled from CNM 0.5 required only 1.447 V at 10 mA cm−2, and had nearly 100% Faraday efficiency and long-term stability (40 h). When used as the electrode for supercapacitors, CNM 0.5 had a large specific capacitance of 1238 F g−1 at 1 A g−1 current density and exceptional durability (85% retention after 2000 cycles). The ASC device assembled with CNM 0.5 provided the high-energy density of 41.2 W h kg−1 and long cycle-life (87% after 2000 cycles). The unique core-shell morphology with abundant active reactive edge sites would be beneficial for charge reduction and the volume shrinking/swelling during the rapid charge/discharge process. The well-ordered and vertically aligned nanosheet arrays possessed good conductivity and small interface resistance, which would facilitate the electron transfer and electrolyte penetration, ion insertion and de-intercalation.

Creating Edge Sites within the 2D Metal‐Organic Framework Boosts Redox Kinetics in Lithium–Sulfur Batteries

AbstractLithium–sulfur batteries have received extensive interest owing to their exceptionally high energy density. Nonetheless, their practical implementation is still impeded by the shuttle effect of polysulfides and sluggish conversion kinetics. Considering that, a porous 2D defective zeolitic imidazolate framework‐7 (ZIF‐7) with abundant active edges is rationally designed as multifunctional sulfur carriers for Li–S batteries. The 2D ZIF‐7 enables uniform distribution of sulfur and rapid Li‐ion diffusion, while rich edges facilitate sufficient exposure to active sites capturing and catalyzing polysulfides. In addition, the nitrogen defects on edge sites can further accelerate the transformation of polysulfides and decrease the energy barrier of Li2S decomposition. Consequently, the Li–S batteries demonstrate surprisingly practical prospects with a stable capacity of 676.9 mAh g−1 over 500 cycles at 1 C (capacity retention rate = 72.3%). When assembled into a pouch cell at 2.3 mg cm−2, it still exhibits a high capacity of 901.1 mAh g−1 after 100 cycles at 0.1 C. This work offers a rational structural design strategy to tackle the challenges of the sulfur cathode.

0D/2D heterojunction of graphene quantum dots/MXene nanosheets for boosted hydrogen evolution reaction

Electrocatalytic hydrogen production is considered to be one of the cleanest hydrogen production pathways, while the development of advanced electrocatalysts with high activity and low cost is currently the biggest challenge in this field. Here, we report a robust and cost-effective approach to the construction of the 0D/2D heterojunctions made from small-sized graphene quantum dots strongly coupled with ultrathin Ti3C2Tx MXene nanosheets (GQDs/Ti3C2Tx) via a controllable assembly process. The newly-designed heterostructure provides unique structural advantages including large specific surface area, uniform dispersion of quantum dots with abundant active edge sites, desirable electronic structures, and good electronic conductivity, which endow the resulting GQDs/Ti3C2Tx catalyst with excellent hydrogen evolution properties with a low onset potential, a small Tafel slope, and long service life, which are significantly better than the bare quantum dots and Ti3C2Tx catalysts.

Two-Dimensional Metal–Organic Frameworks with Unique Oriented Layers for Oxygen Reduction Reaction: Tailoring the Activity through Exposed Crystal Facets

Two-Dimensional Metal–Organic Frameworks with Unique Oriented Layers for Oxygen Reduction Reaction: Tailoring the Activity through Exposed Crystal Facets

A bubble-assisted strategy to prepare porous ultrathin carbon nitride for highly-active photocatalytic hydrogen production

Porous and ultrathin polymetric carbon nitride has recently emerged as a promising photocatalyst. However, the complex synthesis strategy of porous ultrathin carbon nitride (PTCN) impedes its further application in photocatalytic water splitting. It is a challenge to find a facile and powerful synthesis strategy of porous ultrathin polymetric carbon nitride. In this work, we demonstrate a bubble-assisted strategy for porous ultrathin polymetric carbon nitride. The thermal polymerization process under the blowing effect of NH4Cl endows PTCN with the porous and ultrathin structure. The larger accessible specific surface area (SSA) provides abundant active edges and sites, decreasing the diffusion distance of reactants and carriers. Compared to the bulk carbon nitride (bulk CN), PTCN possesses higher SSA, a broader bandgap, and improved photogenerated carriers transfer efficiency. In addition, the calculation of Gibbs free energy manifests the improved hydrogen absorption ability. As a result, a remarkable hydrogen evolution rate at 22.0 mmol h−1 g−1 is achieved, which is 6 times higher than that of bulk carbon nitride.

Engineering Ultrafine NiFe-LDH into Self-Supporting Nanosheets: Separation-and-Reunion Strategy to Expose Additional Edge Sites for Oxygen Evolution.

Here, a strategy is reported to prepare Ni-Fe layered double hydroxide (NiFe-LDH) with abundant exposed edge planes for enhanced oxygen evolution reaction (OER). The edge-to-edge assembly of ultrafine NiFe-LDH directed by graphite-like carbon is performed through a one-step hydrothermal process to form self-supporting nanosheet arrays (named NiFe-LDH/C), in which ascorbic acid is employed as the carbon precursor to control both the platelet size and the assembly mode of NiFe-LDH. Benefiting from the unique structural engineering, NiFe-LDH/C can not only achieve a fast surface reconstruction into the highly active γ-phase structure, but also exposes abundant active edge sites, thus leading to a superior OER performance with the overpotential as low as 234mV at a current density of 50mA cm-2 . Furthermore, density functional theory (DFT) calculations reveal that the unsaturated Fe-sites and the bridge-sites connecting Ni and Fe atoms, which only exist on the edge planes of NiFe-LDH, are the main active centers responsible for promoting the intrinsic OER activity. This work provides a specific and valuable reference for the rational design of high-quality electrocatalysts through structural engineering for renewable energy applications.

Intercalation-induced partial exfoliation of NiFe LDHs with abundant active edge sites for highly enhanced oxygen evolution reaction

Edge sites and interlayer space of NiFe layered double hydroxides (LDHs) play an important role in water oxidation. However, the combined effect of interlayer expansion and partial exfoliation on the catalytic activity is yet to be investigated. Herein, scalable synthesis of partially exfoliated citrate-intercalated NiFe LDHs with tunable interlayer space have been achieved. The effect of citrate concentration on the phase, morphology, surface elemental composition, electronic states of surface metals, and electrochemical properties are comprehensively studied. The unique structure results in improved intrinsic catalytic activity and abundant active edge sites for oxygen evolution reaction. The optimal NiFe LDHs show an overpotential of 225 mV at 10 mA cm−2, which is much smaller than that (∼305 mV) of the single-layer NiFe LDH nanosheets reported in the literature. The high catalytic activity can be mainly attributed to the combined effect between the enlarged interlayer space and the partial exfoliation/nanosheet thickness. That is, the interlayer space is related to the reaction kinetics/mechanism, while the degree of exfoliation affects the magnitude of the current density at a certain potential.