Ni Strongly Coupled with Mo2C Encapsulated in Nitrogen‐Doped Carbon Nanofibers as Robust Bifunctional Catalyst for Overall Water Splitting

It is urgently required to develop highly efficient and stable bifunctional non‐noble metal electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for water splitting. In this study, a facile electrospinning followed by a post‐carbonization treatment to synthesize nitrogen‐doped carbon nanofibers (NCNFs) integrated with Ni and Mo₂C nanoparticles (Ni/Mo₂C‐NCNFs) as water splitting electrocatalysts is developed. Owing to the strong hydrogen binding energy on Mo₂C and high electrical conductivity of Ni, synergetic effect between Ni and Mo₂C nanoparticles significantly promote both HER and OER activities. The optimized hybrid (Ni/Mo₂C(1:2)‐NCNFs) delivers low overpotentials of 143 mV for HER and 288 mV for OER at a current density of 10 mA cm^?2. An alkaline electrolyzer with Ni/Mo₂C(1:2)‐NCNFs as catalysts for both anode and cathode exhibits a current density of 10 mA cm^?2 at a voltage of 1.64 V, which is only 0.07 V larger than the benchmark of Pt/C‐RuO₂ electrodes. In addition, an outstanding long‐term durability during 100 h testing without obvious degradation is achieved, which is superior to most of the noble‐metal‐free electrocatalysts reported to date. This work provides a simple and effective approach for the preparation of low‐cost and high‐performance bifunctional electrocatalysts for efficient overall water splitting.     

Atomically Dispersed Mo Supported on Metallic Co9S8 Nanoflakes as an Advanced Noble‐Metal‐Free Bifunctional Water Splitting Catalyst Working in Universal pH Conditions

Water splitting requires development of cost‐effective multifunctional materials that can catalyze both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) efficiently. Currently, the OER relies on the noble‐metal catalysts; since with other catalysts, its operation environment is greatly limited in alkaline conditions. Herein, an advanced water oxidation catalyst based on metallic Co₉S₈ decorated with single‐atomic Mo (0.99 wt%) is synthesized (Mo‐Co₉S₈@C). It exhibits pronounced water oxidization activity in acid, alkali, and neutral media by showing positive onset potentials of 200, 90, and 290 mV, respectively, which manifests the best Co₉S₈‐based single‐atom Mo catalyst till now. Moreover, it also demonstrates excellent HER performance over a wide pH range. Consequently, the catalyst even outperforms noble metal Pt/IrO₂‐based catalysts for overall water splitting (only requiring 1.68 V in acid, and 1.56 V in alkaline). Impressively, it works under a current density of 10 mA cm^?2 with no obvious decay during a 24 h (0.5 m H₂SO₄) and 72 h (1.0 m KOH) durability experiment. Density functional theory (DFT) simulations reveal that the synergistic effects of atomically dispersed Mo with Co‐containing substrates can efficiently alter the binding energies of adsorbed intermediate species and decrease the overpotentials of the water splitting.     

Eutectic‐Derived Mesoporous Ni‐Fe‐O Nanowire Network Catalyzing Oxygen Evolution and Overall Water Splitting

The development of efficient and abundant water oxidation catalysts is essential for the large‐scale storage of renewable energy in the form of hydrogen fuel via electrolytic water splitting, but still remains challenging. Based upon eutectic reaction and dealloying inheritance effect, herein, novel Ni‐Fe‐O‐based composite with a unique mesoporous nanowire network structure is designed and synthesized. The composite exhibits exceptionally low overpotential (10 mA cm^?2 at an overpotential of 244 mV), low Tafel slope (39 mV dec^?1), and superior long‐term stability (remains 10 mA cm^?2 for over 60 h without degradation) toward oxygen evolution reaction (OER) in 1 m KOH. Moreover, an alkaline water electrolyzer is constructed with the Ni‐Fe‐O composite as catalyst for both anode and cathode. This electrolyzer displays superior electrolysis performance (affording 10 mA cm^?2 at 1.64 V) and long‐term durability. The remarkable features of the catalyst lie in its unique mesoporous nanowire network architecture and the synergistic effect of the metal core and the active metal oxide, giving rise to the strikingly enhanced active surface area, accelerated electron/ion transport, and further promoted reaction kinetics of OER.     

Polydopamine‐Inspired,Dual Heteroatom‐Doped Carbon Nanotubes for Highly Efficient Overall Water Splitting

Overall water splitting involved hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are critical for renewable energy conversion and storage. Heteroatom‐doped carbon materials have been extensively employed as efficient electrocatalysts for independent HER or OER processes, while those as the bifunctional catalysts for simultaneously generating H₂ and O₂ by splitting water have been seldom reported. Inspired by the unparalleled virtues of polydopamine, the authors devise the facile synthesis of nitrogen and sulfur dual‐doped carbon nanotubes with in situ, homogenous and high concentration sulfur doping. The newly developed dual‐doped electrocatalysts display superb bifunctional catalytic activities for both HER and OER in alkaline solutions, outperforming all other reported carbon counterparts. Experimental characterizations confirm that the excellent performance is attributed to the multiple doping together with efficient mass and charge transfer, while theoretical computations reveal the promotion effect of secondary sulfur dopant to enhance the spin density of dual‐doped samples and consequently to form highly electroactive sites for both HER and OER.     

Enhanced Stability and Thickness‐Independent Oxygen Evolution Electrocatalysis of Heterostructured Anodes with Buried Epitaxial Bilayers

Achieving high oxygen evolution reaction (OER) activity while maintaining performance stability is a key challenge for designing perovskite structure oxide OER catalysts, which are often unstable in alkaline environments transforming into an amorphous phase. While the chemical and structural transformation occurring during electrolysis at the electrolyte–catalyst interface is now regarded as a crucial factor influencing OER activity, here, using La_0.7Sr_0.3CoO_3?δ (LSCO) as an active OER catalyst, the critical influence of buried layers on the oxidation current stability in nanoscopically thin, chemically and structurally evolving, catalyst layers is revealed. The use of epitaxial thin films is demonstrated to engineer both depletion layer widths and chemical stability of the catalyst support structure resulting in heterostructured anodes that maintain facile transport kinetics across the electrolyte–anode interface for atomically thin (2–3 unit cells) LSCO catalyst layers and greatly enhanced oxidation current stability as the perovskite structure OER catalysts chemically and structurally transform. This work opens up an approach to design robust and active heterostructured anodes with dynamically evolving ultrathin OER electrocatalyst layers for future green fuel technologies such as conformal coatings of high‐density 3D anode topologies for water splitting.     

A Perovskite Nanorod as Bifunctional Electrocatalyst for Overall Water Splitting

The development of highly efficient and low‐cost electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is paramount for water splitting associated with the storage of clean and renewable energy. Here, this study reports its findings in the development of a nanostructured perovskite oxide as OER/HER bifunctional electrocatalyst for overall water splitting. Prepared by a facile electrospinning method, SrNb_0.1Co_0.7Fe_0.2O_3–δ perovskite nanorods (SNCF‐NRs) display excellent OER and HER activity and stability in an alkaline solution, benefiting from the catalytic nature of perovskites and unique structural features. More importantly, the SNCF‐NR delivers a current density of 10 mA cm^?2 at a cell voltage of merely ≈1.68 V while maintaining remarkable durability when used as both anodic and cathodic catalysts in an alkaline water electrolyzer. The performance of this bifunctional perovskite material is among the best ever reported for overall water splitting, offering a cost‐effective alternative to noble metal based electrocatalysts.     

Earth‐Abundant Iron Diboride (FeB2) Nanoparticles as Highly Active Bifunctional Electrocatalysts for Overall Water Splitting

Developing efficient, durable, and earth‐abundant electrocatalysts for both hydrogen and oxygen evolution reactions is important for realizing large‐scale water splitting. The authors report that FeB₂ nanoparticles, prepared by a facile chemical reduction of Fe²⁺ using LiBH₄ in an organic solvent, are a superb bifunctional electrocatalyst for overall water splitting. The FeB₂ electrode delivers a current density of 10 mA cm^?2 at overpotentials of 61 mV for hydrogen evolution reaction (HER) and 296 mV for oxygen evolution reaction (OER) in alkaline electrolyte with Tafel slopes of 87.5 and 52.4 mV dec^?1, respectively. The electrode can sustain the HER at an overpotential of 100 mV for 24 h and OER for 1000 cyclic voltammetry cycles with negligible degradation. Density function theory calculations demonstrate that the boron‐rich surface possesses appropriate binding energy for chemisorption and desorption of hydrogen‐containing intermediates, thus favoring the HER process. The excellent OER activity of FeB₂ is ascribed to the formation of a FeOOH/FeB₂ heterojunction during water oxidation. An alkaline electrolyzer is constructed using two identical FeB₂‐NF electrodes as both anode and cathode, which can achieve a current density of 10 mA cm^?2 at 1.57 V for overall water splitting with a faradaic efficiency of nearly 100%, rivalling the integrated state‐of‐the‐art Pt/C and RuO₂/C.     

High‐Performance Trifunctional Electrocatalysts Based on FeCo/Co2P Hybrid Nanoparticles for Zinc–Air Battery and Self‐Powered Overall Water Splitting

Currently, it is still a significant challenge to simultaneously boost various reactions by one electrocatalyst with high activity, excellent durability, as well as low cost. Herein, hybrid trifunctional electrocatalysts are explored via a facile one‐pot strategy toward an efficient oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The catalysts are rationally designed to be composed by FeCo nanoparticles encapsuled in graphitic carbon films, Co₂P nanoparticles, and N,P‐codoped carbon nanofiber networks. The FeCo nanoparticles and the synergistic effect from Co₂P and FeCo nanoparticles make the dominant contributions to the ORR, OER, and HER activities, respectively. Their bifunctional activity parameter (?E) for ORR and OER is low to 0.77 V, which is much smaller than those of most nonprecious metal catalysts ever reported, and comparable with state‐of‐the‐art Pt/C and RuO₂ (0.78 V). Accordingly, the as‐assembled Zn–air battery exhibits a high power density of 154 mW cm^?2 with a low charge–discharge voltage gap of 0.83 V (at 10 mA cm^?2) and excellent stability. The as‐constructed overall water‐splitting cell achieves a current density of 10 mA cm^?2 (at 1.68 V), which is comparable to the best reported trifunctional catalysts.     

Ultrafine Pt Nanoparticle‐Decorated Pyrite‐Type CoS2 Nanosheet Arrays Coated on Carbon Cloth as a Bifunctional Electrode for Overall Water Splitting

To improve the utilization efficiency of precious metals, metal‐supported materials provide a direction for fabricating highly active and stable heterogeneous catalysts. Herein, carbon cloth (CC)‐supported Earth‐abundant CoS₂ nanosheet arrays (CoS₂/CC) are presented as ideal substrates for ultrafine Pt deposition (Pt‐CoS₂/CC) to achieve remarkable performance toward the hydrogen and oxygen evolution reactions (HER/OER) in alkaline solutions. Notably, the Pt‐CoS₂/CC hybrid delivers an overpotential of 24 mV at 10 mA cm^?2 and a mass activity of 3.89 A Pt_mg^?1, which is 4.7 times higher than that of commercial Pt/C, at an overpotential of 130 mV for catalyzing the HER. An alkali‐electrolyzer using Pt‐CoS₂/CC as a bifunctional electrode enables a water‐splitting current density of 10 mA cm^?2 at a low voltage of 1.55 V and can sustain for more than 20 h, which is superior to that of the state‐of‐the‐art Pt/C+RuO₂ catalyst. Further experimental and theoretical simulation studies demonstrate that strong electronic interaction between Pt and CoS₂ synergistically optimize hydrogen adsorption/desorption behaviors and facilitate the in situ generation of OER active species, enhancing the overall water‐splitting performance. This work highlights the regulation of interfacial and electronic synergy in pursuit of highly efficient and durable supported catalysts for hydrogen and oxygen electrocatalytic applications.     

Interface Engineering of Hierarchical Branched Mo‐Doped Ni3S2/NixPy Hollow Heterostructure Nanorods for Efficient Overall Water Splitting

Rational design and construction of bifunctional electrocatalysts with excellent activity and durability is imperative for water splitting. Herein, a novel top‐down strategy to realize a hierarchical branched Mo‐doped sulfide/phosphide heterostructure (Mo‐Ni₃S₂/Ni_xP_y hollow nanorods), by partially phosphating Mo‐Ni₃S₂/NF flower clusters, is proposed. Benefitting from the optimized electronic structure configuration, hierarchical branched hollow nanorod structure, and abundant heterogeneous interfaces, the as‐obtained multisite Mo‐Ni₃S₂/Ni_xP_y/NF electrode has remarkable stability and bifunctional electrocatalytic activity in the hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) in 1 m KOH solutions. It possesses an extremely low overpotential of 238 mV at the current density of 50 mA cm^?2 for OER. Importantly, when assembled as anode and cathode simultaneously, it merely requires an ultralow cell voltage of 1.46 V to achieve the current density of 10 mA cm^?2, with excellent durability for over 72 h, outperforming most of the reported Ni‐based bifunctional materials. Density functional theory results further confirm that the doped heterostructure can synergistically optimize Gibbs free energies of H and O‐containing intermediates (OH*, O*, and OOH*) during HER and OER processes, thus accelerating the catalytic kinetics of electrochemical water splitting. This work demonstrates the importance of the rational combination of metal doping and interface engineering for advanced catalytic materials.     

Single Atoms and Clusters Based Nanomaterials for Hydrogen Evolution,Oxygen Evolution Reactions,and Full Water Splitting

The sustainable and scalable production of hydrogen through hydrogen evolution reaction (HER) and oxygen through oxygen evolution reaction (OER) in water splitting demands efficient and robust electrocatalysts. Currently, state‐of‐the‐art electrocatalysts of Pt and IrO₂/RuO₂ exhibit the benchmark catalytic activity toward HER and OER, respectively. However, expanding their practical application is hindered by their exorbitant price and scarcity. Therefore, the development of alternative effective electrocatalysts for water splitting is crucial. In the last few decades, substantial effort has been devoted to the development of alternative HER/OER and water splitting catalysts based on various transition metals (including Fe, Co, Ni, Mo, and atomic Pt) which show promising catalytic activities and durability. In this review, after a brief introduction and basic mechanism of HER/OER, the authors systematically discuss the recent progress in design, synthesis, and application of single atom and cluster‐based HER/OER and water splitting catalysts. Moreover, the crucial factors that can tune the activity of catalysts toward HER/OER and water splitting such as morphology, crystal defects, hybridization of metals with nonmetals, heteroatom doping, alloying, and formation of metals inside graphitic layered materials are discussed. Finally, the existing challenges and future perspectives for improving the performance of electrocatalysts for water splitting are addressed.     

Ultralow Ru Loading Transition Metal Phosphides as High‐Efficient Bifunctional Electrocatalyst for a Solar‐to‐Hydrogen Generation System

Water splitting is a promising technology for sustainable conversion of hydrogen energy. The rational design of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) bifunctional electrocatalysts with superior activity and stability in the same electrolyte is the key to promoting their large‐scale applications. Herein, an ultralow Ru (1.08 wt%) transition metal phosphide on nickel foam (Ru–MnFeP/NF) derived from Prussian blue analogue, that effectively drivies both the OER and the HER in 1 m KOH, is reported. To reach 20 mA cm^?2 for OER and 10 mA cm^?2 for HER, the Ru–MnFeP/NF electrode only requires overpotentials of 191 and 35 mV, respectively. Such high electrocatalytic activity exceeds most transition metal phosphides for the OER and the HER, and even reaches Pt‐like HER electrocatalytic levels. Accordingly, it significantly accelerates full water splitting at 10 mA cm^?2 with 1.470 V, which outperforms that of the integrated RuO₂ and Pt/C couple electrode (1.560 V). In addition, the extremely long operational stability (50 h) and the successful demonstration of a solar‐to‐hydrogen generation system through full water splitting provide more flexibility for large‐scale applications of Ru–MnFeP/NF catalysts.     

Novel Route to Fe‐Based Cathode as an Efficient Bifunctional Catalysts for Rechargeable Zn–Air Battery

Efficient bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts are of great importance for rechargeable metal–air batteries. Herein, FeN_x/C catalysts are synthesized by pyrolysis of thiourea and agarose containing α‐Fe₂O₃ nanoplate as Fe precursor, where α‐Fe₂O₃ nanoplate can prevent the aggregation of carbon sheets to effectively improve the specific surface area during the carbonization process. The FeN_x/C‐700‐20 catalyst displays excellent catalytic performance for both ORR and OER activity in alkaline conditions with more positive onset potential (1.1 V vs the reversible hydrogen electrode) and half‐wave potential, higher stability, and stronger methanol tolerance in alkaline solution, which are all superior to that of the commercial Pt/C catalyst. In this study, the detailed analyses demonstrate that the coexistence of Fe‐based species and high content of Fe‐N_x both play an important role for the catalytic activity. Furthermore, FeN_x/C‐700‐20 as cathode catalyst in Zn–air battery possesses higher charge–discharge stability and power density compared with that of commercial Pt/C catalyst, displaying great potential in practical implementation of for the rechargeable energy devices.     

Highly Active and Stable Graphene Tubes Decorated with FeCoNi Alloy Nanoparticles via a Template‐Free Graphitization for Bifunctional Oxygen Reduction and Evolution

Development of highly active and stable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts from earth‐abundant elements remains a grand challenge for highly demanded reversible fuel cells and metal–air batteries. Carbon catalysts have many advantages over others due to their low cost, excellent electrical conductivity, high surface area, and easy functionalization. However, they typically cannot withstand the highly oxidative OER environment. Here, a new class of bifunctional electrocatalyst is reported, consisting of ultralarge sized nitrogen doped graphene tubes (N‐GTs) (>500 nm) decorated with FeCoNi alloy particles. These tubes are prepared from an inexpensive precursor, dicyandiamide, via a template‐free graphitization process. The ORR/OER activity and the stability of these graphene tube catalysts depend strongly on the transition metal precursors. The best performing FeCoNi‐derived N‐GT catalyst exhibits excellent ORR and OER activity along with adequate electrochemical durability over a wide potential window (0–1.9 V) in alkaline media. The measured OER current is solely due to desirable O₂ evolution, rather than carbon oxidation. Extensive electrochemical and physical characterization indicated that high graphitization degree, thicker tube walls, proper nitrogen doping, and presence of FeCoNi alloy particles are vital for high bifunctional activity and electrochemical durability of tubular carbon catalysts.     

Copper–Nickel Nitride Nanosheets as Efficient Bifunctional Catalysts for Hydrazine‐Assisted Electrolytic Hydrogen Production

Electrocatalytic water splitting is one of the sustainable and promising strategies to generate hydrogen fuel but still remains a great challenge because of the sluggish anodic oxygen evolution reaction (OER). A very effective approach to dramatically decrease the input cell voltage of water electrolysis is to replace the anodic OER with hydrazine oxidation reaction (HzOR) due to its lower thermodynamic oxidation potential. Therefore, developing the low‐cost and efficient HzOR catalysts, coupled with the cathodic hydrogen evolution reaction (HER), is tremendously important for energy‐saving electrolytic hydrogen production. Herein, a new‐type of copper–nickel nitride (Cu₁Ni₂‐N) with rich Cu₄N/Ni₃N interface is rationally constructed on carbon fiber cloth. The 3D electrode exhibits extraordinary HER performance with an overpotential of 71.4 mV at 10 mA cm^?2 in 1.0 m KOH, simultaneously delivering an ultralow potential of 0.5 mV at 10 mA cm^?2 for HzOR in a 1.0 m KOH/0.5 m hydrazine electrolyte. Moreover, the electrolytic cell utilizing the synthesized Cu₁Ni₂‐N electrode as both the cathode and anode display a cell voltage of 0.24 V at 10 mA cm^?2 with an excellent stability over 75 h. The present work develops the promising copper–nickel‐based nitride as a bifunctional electrocatalyst through hydrazine‐assistance for energy‐saving electrolytic hydrogen production.     

Atomically Dispersed Fe‐Nx/C Electrocatalyst Boosts Oxygen Catalysis via a New Metal‐Organic Polymer Supramolecule Strategy

The development of high‐performance oxygen reduction reaction (ORR) catalysts derived from non‐Pt group metals (non‐PGMs) is urgent for the wide applications of proton exchange membrane fuel cells (PEMFCs). In this work, a facile and cost‐efficient supramolecular route is developed for making non‐PGM ORR catalyst with atomically dispersed Fe‐N_x/C sites through pyrolyzing the metal‐organic polymer coordinative hydrogel formed between Fe³⁺ and α‐L‐guluronate blocks of sodium alginate (SA). High‐angle annular dark field scanning transmission electron microscopy (HAADF‐STEM) and X‐ray absorption spectroscopy (XAS) verify that Fe atoms achieve atomic‐level dispersion on the obtained SA‐Fe‐N nanosheets and a possible fourfold coordination with N atoms. The best‐performing SA‐Fe‐N catalyst exhibits excellent ORR activity with half‐wave potential (E_1/2) of 0.812 and 0.910 V versus the reversible hydrogen electrode (RHE) in 0.5 m H₂SO₄ and 0.1 m KOH, respectively, along with respectable durability. Such performance surpasses that of most reported non‐PGM ORR catalysts. Density functional theory calculations suggest that the relieved passivation effect of OH* on Fe‐N₄/C structure leads to its superior ORR activity to Pt/C in alkaline solution. The work demonstrates a novel strategy for developing high‐performance non‐PGM ORR electrocatalysts with atomically dispersed and stable M‐N_x coordination sites in both acidic and alkaline media.     

Selectively Etching Vanadium Oxide to Modulate Surface Vacancies of Unary Metal–Based Electrocatalysts for High‐Performance Water Oxidation

Electrocatalytic water splitting for hydrogen generation is hindered by the sluggish kinetics of water oxidation, and highly efficient electrocatalysts for the oxygen evolution reaction (OER) are urgently required. Numerous bi‐ and multimetal‐based, low‐cost, high‐performance OER electrocatalysts have been developed. However, unary metal–based high‐performance electrocatalysts are seldom reported. In the present study, Co₂(OH)₃Cl/vanadium oxide (VO_y) composites are synthesized, from which VO_y is completely etched out by a simple cyclic voltammetry treatment, which simultaneously transforms Co₂(OH)₃Cl in situ to ultrafine CoOOH. The selective removal of VO_y modulates the nature of the surface in the obtained CoOOH by creating surface oxygen vacancies (V_o), along with disordered grain boundaries. The best‐performing CoOOH with optimum V_o is found to be associated with a low overpotential of 282 mV at 10 mA cm^?2 catalytic current density on a simple glassy carbon electrode for OER. This facile protocol of selectively etching VO_y to modulate the nature of the surface is successfully applied to synthesize another Fe‐based electrocatalyst with high OER performance, thus establishing its utility for unary metal–based electrocatalyst synthesis.     

All‐In‐One Perovskite Catalyst: Smart Controls of Architecture and Composition toward Enhanced Oxygen/Hydrogen Evolution Reactions

A conventional water electrolyzer consists of two electrodes, each of which is embedded with a costly and rare electrocatalyst, typically IrO₂/C for oxygen evolution reaction (OER) and Pt/C for hydrogen evolution reaction (HER), respectively. HER and OER electrocatalysts usually require very different pH values to keep them stable and active. Thus, the development of earth‐abundant nonprecious metal catalysts for both HER and OER is of great importance to practical applications. This work reports the results of integrated water electrolysis using the hybrids of electrospun La_0.5(Ba_0.4Sr_0.4Ca_0.2)_0.5Co_0.8Fe_0.2O_3–δ (L‐0.5) perovskite nanorods attached to reduced graphene oxide (rGO) nanosheets as bifunctional electrodes. Via rationalizing the composition and morphology of L‐0.5/rGO nanohybrids, excellent catalytic performance and stability toward OER and HER are achieved in alkaline media. The operating voltage of integrated L‐0.5/rGO electrolyzer is tested to be 1.76 V at 50 mA cm^–2, which is close to that of the commercially available IrO₂/C‐Pt/C couple (1.76 V @ 50 mA cm^–2). Such a bifunctional electrocatalyst could be extended toward practical electrolysis use with low expanse and high efficiency. More generally, the protocol described here broadens our horizons in terms of the designs and the diverse functionalities of catalysts for use in various applications.     

Electroless Plating of Highly Efficient Bifunctional Boride‐Based Electrodes toward Practical Overall Water Splitting

Exploring highly‐efficient and low‐cost electrodes for both hydrogen and oxygen evolution reaction (HER and OER) is of primary importance to economical water splitting. Herein, a series of novel and robust bifunctional boride‐based electrodes are successfully fabricated using a versatile Et₂NHBH₃‐involved electroless plating (EP) approach via deposition of nonprecious boride‐based catalysts on various substrates. Owing to the unique binder‐free porous nodule structure induced by the hydrogen release EP reaction, most of the nonprecious boride‐based electrodes are highly efficient for overall water splitting. As a distinctive example, the Co‐B/Ni electrode can afford 10 mA cm^?2 at overpotentials of only 70 mV for HER and 140 mV for OER, and can also survive at large current density of 1000 mA cm^?2 for over 20 h without performance degradation in 1.0 m KOH. Several boride‐based two‐electrode electrolyzers can achieve 10 mA cm^?2 at low voltages of around 1.4 V. Moreover, the facile EP approach is economically viable for flexible and large size electrode production.     

Multifunctional Single‐Crystallized Carbonate Hydroxides as Highly Efficient Electrocatalyst for Full Water splitting

The controllable synthesis of single‐crystallized iron‐cobalt carbonate hydroxide nanosheets array on 3D conductive Ni foam (FCCH/NF) as a monolithic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) bifunctional electrocatalyst for full water splitting is described. The results demonstrate that the incorporation of Fe can effectively tune the morphology, composition, electronic structure, and electrochemical active surface area of the electrocatalysts, thus greatly enhancing the intrinsic electrocatalytic activity. The optimal electrocatalyst (F_0.25C₁CH/NF) can deliver 10 and 1000 mA cm^?2 at very small overpotentials of 77 and 256 mV for HER and 228 and 308 mV for OER in 1.0 m KOH without significant interference from gas evolution. The F_0.25C₁CH‐based two‐electrode alkaline water electrolyzer only requires cell voltages of 1.45 and 1.52 V to achieve current densities of 10 and 500 mA cm^?2. The results demonstrate that such fascinating electrocatalytic activity can be ascribed to the increase in the catalytic active surface area, facilitated electron and mass transport properties, and the synergistic interactions because of the incorporation of Fe.