Constructing Symmetry-Mismatched RuxFe3-xO4 Heterointerface-Supported Ru Clusters for Efficient Hydrogen Evolution and Oxidation Reactions.

Ru-related catalysts have shown excellent performance for the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR); however, a deep understanding of Ru-active sites on a nanoscale heterogeneous support for hydrogen catalysis is still lacking. Herein, a click chemistry strategy is proposed to design Ru cluster-decorated nanometer RuxFe3-xO4 heterointerfaces (Ru/RuxFe3-xO4) as highly effective bifunctional hydrogen catalysts. It is found that introducing Ru into nanometric Fe3O4 species breaks the symmetry configuration and optimizes the active site in Ru/RuxFe3-xO4 for HER and HOR. As expected, the catalyst displays prominent alkaline HER and HOR performance with mass activity much higher than that of commercial Pt/C as well as robust stability during catalysis because of the strong interaction between the Ru cluster and the RuxFe3-xO4 support, and the optimized adsorption intermediate (Had and OHad). This work sheds light on a promsing approach to improving the electrocatalysis performance of catalysts by the breaking of atomic dimension symmetry.

Boron-Induced Interstitial Effects Drive Water Oxidation on Ordered Ir-B Compounds.

Interstitial filling of light atoms strongly affects the electronic structure and adsorption properties of the parent catalyst due to ligand and ensemble effects. Different from the conventional doping and surface modification, constructing ordered intermetallic structures is more promising to overcome the dissolution and reconstruction of active sites through strong interactions generated by atomic periodic arrangement, achieving joint improvement in catalytic activity and stability. However, for tightly arranged metal lattices, such as iridium (Ir), obtaining ordered filling atoms and further unveiling their interstitial effects are still limited by highly activated processes. Herein, we report a high-temperature molten salt assisted strategy to form the intermetallic Ir-B compounds (IrB1.1) with ordered filling by light boron (B) atoms. The B residing in the interstitial lattice of Ir constitutes favorable adsorption surfaces through a donor-acceptor architecture, which has an optimal free energy uphill in rate-determining step (RDS) of oxygen evolution reaction (OER), resulting in enhanced activity. Meanwhile, the strong coupling of Ir-B structural units suppresses the demetallation and reconstruction behavior of Ir, ensuring catalytic stability. Such B-induced interstitial effects endow IrB1.1 with higher OER performance than commercial IrO2, which is further validated in proton exchange membrane water electrolyzers (PEMWEs).

Symmetry-Broken Ru Nanoparticles with Parasitic Ru-Co Dual-Single Atoms Overcome the Volmer Step of Alkaline Hydrogen Oxidation.

Efficient dual-single-atom catalysts are crucial for enhancing atomic efficiency and promoting the commercialization of fuel cells, but addressing the sluggish kinetics of hydrogen oxidation reaction (HOR) in alkaline media and the facile dual-single-atom site generation remains formidable challenges. Here, we break the local symmetry of ultra-small ruthenium (Ru) nanoparticles by embedding cobalt (Co) single atoms, which results in the release of Ru single atoms from Ru nanoparticles on reduced graphene oxide (Co1 Ru1,n /rGO). In situ operando spectroscopy and theoretical calculations reveal that the oxygen-affine Co atom disrupts the symmetry of ultra-small Ru nanoparticles, resulting in parasitic Ru and Co dual-single-atom within Ru nanoparticles. The interaction between Ru single atoms and nanoparticles forms effective active centers. The parasitism of Co atoms modulates the adsorption of OH intermediates on Ru active sites, accelerating HOR kinetics through faster formation of *H2 O. As anticipated, Co1 Ru1,n /rGO exhibits ultrahigh mass activity (7.68 A mgRu -1 ) at 50 mV and exchange current density (0.68 mA cm-2 ), which are 6 and 7 times higher than those of Ru/rGO, respectively. Notably, it also displays exceptional durability surpassing that of commercial Pt catalysts. This investigation provides valuable insights into hybrid multi-single-atom and metal nanoparticle catalysis.

Fe-Regulated Amorphous-Crystal Ni(Fe)P2 Nanosheets Coupled with Ru Powerfully Drive Seawater Splitting at Large Current Density.

Water electrolysis is an ideal method for industrial green hydrogen production. However, due to increasing scarcity of freshwater, it is inevitable to develop advanced catalysts for electrolyzing seawater especially at large current density. This work reports a unique Ru nanocrystal coupled amorphous-crystal Ni(Fe)P2 nanosheet bifunctional catalyst (Ru-Ni(Fe)P2 /NF), caused by partial substitution of Fe to Ni atoms in Ni(Fe)P2 , and explores its electrocatalytic mechanism by density functional theory (DFT) calculations. Owing to high electrical conductivity of crystalline phases, unsaturated coordination of amorphous phases, and couple of Ru species, Ru-Ni(Fe)P2 /NF only requires overpotentials of 375/295 and 520/361 mV to drive a large current density of 1 A cm-2 for oxygen/hydrogen evolution reaction (OER/HER) in alkaline water/seawater, respectively, significantly outperforming commercial Pt/C/NF and RuO2 /NF catalysts. In addition, it maintains stable performance at large current density of 1 A cm-2 and 600 mA cm-2 for 50 h in alkaline water and seawater, respectively. This work provides a new way for design of catalysts toward industrial-level seawater splitting.

Effect of B-Doping and Manifestation on TiO2-Supported IrO2 for Oxygen Evolution Reaction in Water Electrolysis.

To commercialize hydrogen production by proton exchange membrane (PEM) electrolysis, the amount of rare and precious metal (iridium) required for anodic oxygen evolution reaction (OER) must be greatly reduced. In order to solve the problem, carrier loading is used to reduce the amount of iridium. Unlike the carrier modified by conventional metal element doping, this work doped the carrier with the nonmetallic element and then prepared IrO2/TiBxO2 composite catalyst using the Adams melting method. B-doped TiO2 supports with different doping amounts show the main phase rutile structure. Among them, the conductivity of B-doped carrier shows an increasing trend with the increase of doping amount, because boron can form holes and negative centers after doping, and more carriers improve the conductivity of the support. In addition, since element B is manifested from inside to outside on the support, B can affect the catalytic process. After the manifestation of element B, the carrier loaded with IrO2 exhibited superior electrocatalytic properties. The voltammetric charge per unit mass of 40IrO2/TiB0.3O2#2 (where #2 represents B after manifestation) reaches 1970 mC (cm2 mg)-1, the corresponding overpotential is 273 mV at a current density of 10 mA/cm-2, and the Tafel slope is 61.9 mV/dec Also, the charge transfer resistance is only 15 Ω. Finally, in the stability test, the composite catalyst is also better than pure IrO2 in the 20 000 s operation. Therefore, element B has an unexpectedly positive effect on the catalytic progress on the surface of the support after its manifestation.

Ge-Regulated Ordered Phase in Pseudosphere-Structured LiNi0.5Mn1.5O4 Spinel Effectively Inhibits Mn Dissolution.

Due to the higher energy density, high thermal stability, and low cost, LiNi0.5Mn1.5O4 (LNMO) spinel, with a large voltage operating window, has been one of the most promising cathode materials for lithium-ion batteries (LIBs). However, the interfacial reaction between the cathode and electrolyte and the two-phase reaction within the bulk of LNMO would destroy the original structure and lead to capacity deterioration, posing a significant challenge. Therefore, the way to suppress the transition-metal (TM) dissolution in LNMO has attracted much attention. However, the ordered/disordered phase regulation by metal atom doping to prohibit TM dissolution has not been extensively explored. Herein, a Ge-doping strategy is proposed to adjust the ratio of disordered/ordered phases in LNMO, resulting in exceptional structural stability. For the modified spinel cathode, there is almost no voltage drop and the capacity retention is up to 92.2% over 1000 cycles at 1C. These results demonstrate that incorporating Ge into LNMO forms a robust structure that effectively increases the amount of Mn4+ while blocking the diffusion of TM ions. In addition, Ge-doping also protects the bulk from further reactions with electrolytes, significantly enhancing the interfacial stability and relieving voltage decay in cycling. This approach can also be applied to design other high-stability cathodes through ordered/disordered phase regulation.

Geometric Engineering of Porous PtCu Nanotubes with Ultrahigh Methanol Oxidation and Oxygen Reduction Capability.

Platinum (Pt), as a commonly used electrocatalyst in direct methanol fuel cells (DMFCs), suffers from sluggish kinetics of both the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). Geometric engineering has been proven effective for improving the MOR and ORR activities. Thus, by modulating the Pt precursor and poly(vinylpyrrolidone) (PVP) dosages, different porous PtCu nanotubes constructed by hollow nanospheres, solid alloy, and Pt-rich skinned nanoparticles, respectively, are successfully synthesized. Among them, the solid PtCu alloy nanoparticle coherent nanotubes exhibit the specific activity 9.42 times higher than Pt/C toward MOR, while the hollow PtCu alloy nanosphere coherent nanotubes show the specific activity 4.85 times higher than Pt/C toward ORR. The different Pt:Cu ratios of hollow nanospheres, solid alloy, and Pt-rich skinned nanoparticles cause the differences in electron transfer from Cu to Pt as well as electronic structures of Pt. As a result, the binding energies of intermediates can be regulated, leading to the enhancement in MOR and ORR.

Fe-Incorporated Ni/MoO2 Hollow Heterostructure Nanorod Arrays for High-Efficiency Overall Water Splitting in Alkaline and Seawater Media.

Developing high-efficiency and cost-effective bifunctional catalysts for water electrolysis is fascinating but still remains challenging. Thus, diverse strategies have been utilized to boost the activity toward oxygen/hydrogen evolution reactions (OER/HER) for water splitting. Among them, composition and structure engineering as an effective strategy has received extensive attention. Here, by means of a self-sacrificing template strategy and simultaneous regulation of the composition and structure, Fe-incorporated Ni/MoO2 heterostructural (NiFe/Fe-MoO2 ) hollow nanorod arrays are designed and constructed. Benefiting from abundant catalytic active sites, high intrinsic activity, and fast reaction kinetics, NiFe/Fe-MoO2 exhibits superior OER (η20  = 213 and 219 mV) and Pt-like HER activity (η10  = 34 and 38 mV), respectively, in 1 m KOH and alkaline seawater media. This results in attractive prospects in alkaline water and seawater electrolysis with only voltages of 1.48 and 1.51 V, and 1.69 and 1.73 V to achieve current densities of 10 and 100 mA cm-2 , respectively, superior to the Pt/C and RuO2 pair as a benchmark. Undoubtedly, this work provides a beneficial approach to the design and construction of noble-metal-free bifunctional catalysts toward efficient hydrogen production from alkaline water and seawater electrolysis.

Ru-Incorporated Nickel Diselenide Nanosheet Arrays with Accelerated Adsorption Kinetics toward Overall Water Splitting.

Developing high-efficiency electrocatalysts toward overall water splitting is an increasingly important area for sustainable energy evolution. Theoretical calculation results demonstrate that the incorporation of Ru optimizes the Gibbs free energy of adsorption of H2 O molecules and intermediates for the hydrogen/oxygen evolution reactions (HER/OER) on metal selenide sites, thus boosting electrocatalytic overall water splitting. Accordingly, ruthenium modified nickel diselenide nanosheet arrays are designed and construct on nickel foam (Ru-NiSe2 /NF). The obtained Ru-NiSe2 /NF electrode with a stable 3D structure shows greatly improved OER and HER activity in alkaline solution. Particularly, toward OER, it only requires 210 mV to obtain a current density of 10 mA cm-2 , and the formation of the intermediate nickel oxyhydroxide as active center during the OER process is captured by in situ Raman. Moreover, the overall water splitting can be driven by a voltage of merely 1.537 V to obtain 10 mA cm-2 . This work provides an available strategy for selenides to enhance electrochemical properties and inspires more studies to explore highly efficient electrocatalysts toward full water splitting.

Competitive Coordination-Pairing between Ru Clusters and Single-Atoms for Efficient Hydrogen Evolution Reaction in Alkaline Seawater.

The coordination environment of Ru centers determines their catalytic performance, however, much less attention is focused on cluster-induced charge transfer in a Ru single-atom system. Herein, by density functional theory (DFT) calculations, a competitive coordination-pairing between Ru clusters (RuRu bond) and single-atoms (RuO bond) is revealed leading to the charge redistribution between Ru and O atoms in ZnFe2 O4 units which share more free electrons to participate in the hydrogen desorption process, optimizing the proton adsorption and hydrogen desorption. Thus, a clicking confinement strategy for building a competitive coordination-pairing between Ru clusters and single-atoms anchored on ZnFe2 Ox nanosheets over carbon via RuO ligand (Ru1, n -ZnFe2 Ox -C) is proposed. Benefiting from the optimized coordination effect and the electronic synergy between Ru clusters and single-atoms, such a catalyst demonstrates the excellent activity and excellent stability in alkaline and seawater media, which has exceptional hydrogen evolution reaction activity with overpotentials as low as 10.1 and 15.9 mV to reach the current density of 10 mA cm-2 in alkaline and seawater media, respectively, higher than that of commercial Pt/C catalysts as a benchmark. Furthermore, it owns remarkably outstanding mass activity, approximately 2 and 8 times higher than that of Pt catalysts in alkaline and seawater media, respectively.

Cation/Anion Dual-Vacancy Pair Modulated Atomically-Thin Sex -Co3 S4 Nanosheets with Extremely High Water Oxidation Performance in Ultralow-Concentration Alkaline Solutions.

The density functional theory calculation results reveal that the adjacent defect concentration and electronic spin state can effectively activate the CoIII sites in the atomically thin nanosheets, facilitating the thermodynamic transformation of *O to *OOH, thus offering ultrahigh charge transfer properties and efficiently stabilizing the phase. This undoubtedly evidences that, for metal sulfides, the atom-scale cation/anion vacancy pair and surface electronic spin state can play a great role in enhancing the oxygen evolution reaction. Inspired by the theoretical prediction, interconnected selenium (Se) wired ultrathin Co3 S4 (Sex -Co3 S4 ) nanosheets with Co/S (Se) dual-vacancies (Se1.0 -Co3 S4 -VS/Se -VCo ) pairs are constructed by a simple approach. As an efficient sulfur host material, in an ultralow-concentration KOH solution (0.1 m), Se1.0 -Co3 S4 -VS/Se -VCo presents outstanding durability up to 165 h and a low overpotential of 289.5 mV at 10 mA cm-2 , which outperform the commercial Co3 S4 nanosheets (NSs) and RuO2 . Moreover, the turnover frequency of Se1.0 -Co3 S4 -VS/Se -VCo is 0.00965 s-1 at an overpotential of 0.39 V, which is 5.7 times that of Co3 S4 NSs, and 5.8 times that of commercial RuO2 . The finding offers a rational design strategy to create the multi-defect structure in catalysts toward high-efficiency water electrolysis.

Inhibiting Mn Migration by Sb-Pinning Transition Metal Layers in Lithium-Rich Cathode Material for Stable High-Capacity Properties.

Owing to the interacted anion and cation redox dynamics in Li2 MnO3 , the high energy density can be obtained for lithium-rich manganese-based layered transition metal (TM) oxide [Li1.2 Ni0.2 Mn0.6 O2 , LNMO]. However, irreversible migration of Mn ions and oxygen release during highly de-lithiation can destroy its layered structure, leading to voltage and capacity decline. Herein, non-TM antimony (Sb) is pinned to the TM layer of LNMO by a facile sol-gel method. High-resolution ex and in situ characterization technologies manifest that the introduction of trace Sb inhibits the migration of Mn ions, forming a more stable structure. Sb can impressively adjust the Mn-O interaction between anions and cations, beneficial to decrease the energy level of Mn 3d and O 2p orbitals and expand their band gap according to the  theoretical calculation results. As a result, the discharge specific capacity and the energy density for SbLi1.2 [Ni0.2 Mn0.6 ]O2 (SLNMO) reaches as high as 301 mAh g-1 and 1019.6 Wh kg-1 at 0.1 C, respectively. Moreover, the voltage decay is reduced by 419.8 mV compared with LNMO. The regulative interaction between Mn 3d and isolated O 2p bands provides an accurate guidance for solving electrochemical performance deficiencies of lithium-rich manganese-based cathode oxide.

Work-function-induced Interfacial Built-in Electric Fields in Os-OsSe2 Heterostructures for Active Acidic and Alkaline Hydrogen Evolution.

Theoretical calculations unveil that the formation of Os-OsSe2 heterostructures with neutralized work function (WF) perfectly balances the electronic state between strong (Os) and weak (OsSe2 ) adsorbents and bidirectionally optimizes the hydrogen evolution reaction (HER) activity of Os sites, significantly reducing thermodynamic energy barrier and accelerating kinetics process. Then, heterostructural Os-OsSe2 is constructed for the first time by a molten salt method and confirmed by in-depth structural characterization. Impressively, due to highly active sites endowed by the charge balance effect, Os-OsSe2 exhibits ultra-low overpotentials for HER in both acidic (26 mV @ 10 mA cm-2 ) and alkaline (23 mV @ 10 mA cm-2 ) media, surpassing commercial Pt catalysts. Moreover, the solar-to-hydrogen device assembled with Os-OsSe2 further highlights its potential application prospects. Profoundly, this special heterostructure provides a new model for rational selection of heterocomponents.

Ultralow Ru Incorporated Amorphous Cobalt-Based Oxides for High-Current-Density Overall Water Splitting in Alkaline and Seawater Media.

Realizing efficiency and stable hydrogen production by water electrolysis under high current densities is essential to the forthcoming hydrogen economy. However, its industrial breakthrough is seriously limited by bifunctional catalysts with slow hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalytic processes. Herein, an ultralow Ru incorporated amorphous cobalt-based oxide (Ru-CoOx /NF), effectively driving the electrolysis of water at high current densities in alkaline water and seawater, is designed and constructed. In 1 m KOH, to reach the current density of 1000 mA cm-2 for HER and OER, it only needs 252 and 370 mV overpotentials, respectively, beyond commercial Pt/C and RuO2 catalysts. At the high current density, it also presents outstanding electrochemical stability. Then the electrolyzer apparatus assembled with Ru-CoOx /NF, just requires the ultra-low voltage of 2.2 and 2.62 V to support the current density of 1000 mA cm-2 in alkaline water and seawater electrolysis, respectively, for hydrogen production, better than that of the commercial Pt/C and RuO2 catalysts. This work demonstrates that Ru-CoOx /NF is one of the most promising catalysts for industrial applications and provides a possibility for exploration of high-current-density water electrocatalysis by changing the crystallinity of the catalyst.

Sulfate Ions Induced Concave Porous S-N Co-Doped Carbon Confined FeCx Nanoclusters with Fe-N4 Sites for Efficient Oxygen Reduction in Alkaline and Acid Media.

To improve the catalytic activity of the catalysts, it is key to intensifying the intrinsic activity of active sites or increasing the exposure of accessible active sites. In this work, an efficient oxygen reduction electrocatalyst is designed that confines plentiful FeCx nanoclusters with Fe-N4 sites in a concave porous S-N co-doped carbon matrix, readily accessible for the oxygen reduction reaction (ORR). Sulfate ions react with the carbon derived from ZIF-8 at high temperatures, leading to the shrinkage of the carbon framework and then forming a concave structure with abundant macropores and mesopores with S incorporation. Such an architecture promotes the exposure of active sites and accelerates remote mass transfer. As a result, the catalyst (Fe/S-NC) with a large number of C-S-C, Fe-N4 , and FeCx nanoclusters presents impressive ORR activity and stability. In alkaline media, the half-wave potential of the best catalyst (Fe/S2 -NC) is 0.91 V, which far exceeds that of commercial platinum carbon (0.85 V), while in acidic media the half-wave potential reaches 0.784 V, comparable to platinum carbon (0.812 V). Furthermore, for the zinc-air battery, the outstanding peak power density of Fe/S2 -NC (170 mW cm-2 ) superior to platinum carbon (108 mW cm-2 ) also highlights its great application potential.

Molybdenum Carbide-PtCu Nanoalloy Heterostructures on MOF-Derived Carbon toward Efficient Hydrogen Evolution.

In this study, PtCu-Mo2 C heterostructure with charge redistribution is investigated via first-principles theoretical calculations. Mo2 C can promote the formation of the electron-rich region of PtCu as an active site, displaying an optimized adsorption behavior toward hydrogen in terms of reduced thermodynamic energy barriers. Owing to the attractive density functional theory calculation results, the PtCu-Mo2 C heterostructure is fabricated via carbonization of the unique metal-organic framework (MOF) followed by the replacement reduction reaction for the first time. Owing to its swift kinetics and outstanding specific activity, it exhibits high hydrogen evolution reaction (HER) catalytic activity (26 mV @ 10 mA cm-2 ) and superior mass activity (1 A mgPt -1 at -0.04 V) in acidic media, which is approximately six times that of commercial Pt/C catalysts. The perception of the intrinsic activity origin of the alloy with an excellent structural support can guide the development of Pt-based and other alloy catalysts in future.

Anion Modulation of Pt-Group Metals and Electrocatalysis Applications.

Pt-group metal (PGM) electrocatalysts with unique electronic structures and irreplaceable comprehensive properties play crucial roles in electrocatalysis. Anion engineering can create a series of PGM compounds (such as RuP2 , IrP2 , PtP2 , RuB2 , Ru2 B3 , RuS2 , etc.) that provide a promising prospect for improving the electrocatalytic performance and use of Pt-group noble metals. This review seeks the electrochemical activity origin of anion-modulated PGM compounds, and systematically analyzes and summarizes their synthetic strategies and energy-relevant applications in electrocatalysis. Orientation towards the sustainable development of nonfossil resources has stimulated a blossoming interest in the design of advanced electrocatalysts for clean energy conversion. The anion-modulated strategy for Pt-group metals (PGMs) by means of anion engineering possesses high flexibility to regulate the electronic structure, providing a promising prospect for constructing electrocatalysts with superior activity and stability to satisfy a future green electrochemical energy conversion system. Based on the previous work of our group and others, this review summarizes the up-to-date progress on anion-modulated PGM compounds (such as RuP2 , IrP2 , PtP2 , RuB2 , Ru2 B3 , RuS2 , etc.) in energy-related electrocatalysis from the origin of their activity and synthetic strategies to electrochemical applications including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), N2 reduction reaction (NRR), and CO2 reduction reaction (CO2 RR). At the end, the key problems, countermeasures and future development orientations of anion-modulated PGM compounds toward electrocatalytic applications are proposed.

Regulative Electronic States around Ruthenium/Ruthenium Disulphide Heterointerfaces for Efficient Water Splitting in Acidic Media.

Theoretical calculations unveil the charge redistribution over abundant interfaces and the enhanced electronic states of Ru/RuS2 heterostructure. The resulting surface electron-deficient Ru sites display optimized adsorption behavior toward diverse reaction intermediates, thereby reducing the thermodynamic energy barriers. Experimentally, for the first time the laminar Ru/RuS2 heterostructure is rationally engineered by virtue of the synchronous reduction and sulfurization under eutectic salt system. Impressively, it exhibits extremely high catalytic activity for both OER (201 mV @ 10 mA cm-2 ) and HER (45 mV @ 10 mA cm-2 ) in acidic media due to favorable kinetics and excellent specific activity, consequently leading to a terrific performance in acidic overall water splitting devices (1.501 V @ 10 mA cm-2 ). The in-depth insight into the internal activity origin of interfacial effect could offer precise guidance for the rational establishment of hybrid interfaces.

Synergistic Coupling of Ni Nanoparticles with Ni3 C Nanosheets for Highly Efficient Overall Water Splitting.

Exploring earth-abundant bifunctional electrocatalysts with high efficiency for water electrolysis is extremely demanding and challenging. Herein, density functional theory (DFT) predictions reveal that coupling Ni with Ni3 C can not only facilitate the oxygen evolution reaction (OER) kinetics, but also optimize the hydrogen adsorption and water adsorption energies. Experimentally, a facile strategy is designed to in situ fabricate Ni3 C nanosheets on carbon cloth (CC), and simultaneously couple with Ni nanoparticles, resulting in the formation of an integrated heterostructure catalyst (Ni-Ni3 C/CC). Benefiting from the superior intrinsic activity as well as the abundant active sites, the Ni-Ni3 C/CC electrode demonstrates excellent bifunctional electrocatalytic activities toward the OER and hydrogen evolution reaction (HER), which are superior to all the documented Ni3 C-based electrocatalysts in alkaline electrolytes. Specifically, the Ni-Ni3 C/CC catalyst exhibits the low overpotentials of only 299 mV at the current density of 20 mA cm-2 for the OER and 98 mV at 10 mA cm-2 for the HER in 1 m KOH. Furthermore, the bifunctional Ni-Ni3 C/CC catalyst can propel water electrolysis with excellent activity and nearly 100% faradic efficiency. This work highlights an easy approach for designing and constructing advanced nickel carbide-based catalysts with high activity based on the theoretical predictions.

Twinned Tungsten Carbonitride Nanocrystals Boost Hydrogen Evolution Activity and Stability.

Synergistic integration of two active metal-based compounds can lead to much higher electrocatalytic activity than either of the two individually, due to the interfacial effects. Herein, a proof-of-concept strategy is creatively developed for the successful fabrication of twinned tungsten carbonitride (WCN) nanocrystals, where W2 C and WN are chemically bonded at the molecule level. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) spectroscopy analyses demonstrate that the intergrowth of W2 C and WN in the WCN nanocrystals produces abundant N-W-C interfaces, leading to a significant enhancement in catalytic activity and stability for hydrogen evolution reaction (HER). Indeed, it shows 14.2 times higher and 140 mV lower in the respective turn-over frequency (TOF) and overpotential at 10 mA cm-2 compared to W2 C alone. To complement the experimental observation, the theoretical calculations demonstrate that the WCN endows more favorable hydrogen evolution reaction than the single W2 C or WN crystals due to abundant interfaces, beneficial electronic states, lower work function, and more active W sites at the N-W-C interfaces.