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The design of high‐entropy single‐atom catalysts (HESAC) with 5.2 times higher entropy compared to single‐atom catalysts (SAC) is proposed, by using four different metals (FeCoNiRu‐HESAC) for oxygen reduction reaction (ORR). Fe active sites with intermetallic distances of 6.1 Å exhibit a low ORR overpotential of 0.44 V, which originates from weakening the adsorption of OH intermediates. Based on density functional theory (DFT) findings, the FeCoNiRu‐HESAC with a nitrogen‐doped sample were synthesized. The atomic structures are confirmed with X‐ray photoelectron spectroscopy (XPS), X‐ray absorption (XAS), and scanning transmission electron microscopy (STEM). The predicted high catalytic activity is experimentally verified, finding that FeCoNiRu‐HESAC has overpotentials of 0.41 and 0.37 V with Tafel slopes of 101 and 210 mVdec−1 at the current density of 1 mA cm−2 and the kinetic current densities of 8.2 and 5.3 mA cm−2, respectively, in acidic and alkaline electrolytes. These results are comparable with Pt/C. The FeCoNiRu‐HESAC is used for Zinc–air battery applications with an open circuit potential of 1.39 V and power density of 0.16 W cm−2. Therefore, a strategy guided by DFT is provided for the rational design of HESAC which can be replaced with high‐cost Pt catalysts toward ORR and beyond. [ABSTRACT FROM AUTHOR]

Urea oxidation reaction (UOR) has been utilized to substitute the oxygen evolution reaction (OER), to escalate the energy conversion efficiency in electrochemical hydrogen generation processes with denitrification of widespread urea in wastewater. This study reports breakthroughs in Ni‐based UOR electrocatalysts, particularly with NiFe oxalate (O‐NFF), derived from Ni3Fe alloy foam with prismatic nanostructures and elevated surface area. The O‐NFF achieves cutting‐edge performances, representing 500 mA cm−2 of current density at 1.47 V RHE and exceptionally low Tafel slope of 12.1 mV dec−1 (in 1 m KOH with 0.33 m urea). X‐ray photoelectron/absorption spectroscopy (XPS/XAS) coupled with density functional theory calculations unveil that oxalate ligands induce charge deficient Ni center, promoting stable urea‐O adsorption. Furthermore, Fe dopants enhance oxalate‐O charge density and H‐bond strength, facilitating C‐N cleavage for N2 and NO2− formation. The extraordinary UOR kinetics by the tandem effects of oxalate and Fe prevent Ni over‐oxidation, corroborated by operando XAS, minimizing OER interference. It agrees with an adaptive reconstruction to Fe‐doped β‐NiOOH on top surface in extended urea electrolysis with marginal loss in UOR kinetics. This findings shed light to bimetal‐organic‐framework as (pre)catalysts to improve industrial electrolytic H2 production. [ABSTRACT FROM AUTHOR]

To realize economically feasible electrochemical CO2 conversion, achieving a high partial current density for value-added products is particularly vital. However, acceleration of the hydrogen evolution reaction due to cathode flooding in a high-current-density region makes this challenging. Herein, we find that partially ligand-derived Ag nanoparticles (Ag-NPs) could prevent electrolyte flooding while maintaining catalytic activity for CO2 electroreduction. This results in a high Faradaic efficiency for CO (>90%) and high partial current density (298.39 mA cm‒2), even under harsh stability test conditions (3.4 V). The suppressed splitting/detachment of Ag particles, due to the lipid ligand, enhance the uniform hydrophobicity retention of the Ag-NP electrode at high cathodic overpotentials and prevent flooding and current fluctuations. The mass transfer of gaseous CO2 is maintained in the catalytic region of several hundred nanometers, with the smooth formation of a triple phase boundary, which facilitate the occurrence of CO2RR instead of HER. We analyze catalyst degradation and cathode flooding during CO2 electrolysis through identical-location transmission electron microscopy and operando synchrotron-based X-ray computed tomography. This study develops an efficient strategy for designing active and durable electrocatalysts for CO2 electrolysis. A key factor for the electrochemical reduction of CO2 to CO is limiting the competing H2 evolution reaction. Here, authors use real-time synchrotron X-ray computed tomography to show that a silver nanoparticle-ligand catalyst structure improves water management, thereby maintaining CO production. [ABSTRACT FROM AUTHOR]

Although great efforts on the delicate construction of a built‐in electric field (BIEF) to modify the electronic properties of active sites have been conducted, the substantial impact of BIEF coupled with electrode potential on the electrochemical reactions has not been clearly investigated. Herein, we designed an alkaline hydrogen evolution reaction (HER) catalyst composed of heterogeneous Ru−CoP urchin arrays on carbon cloth (Ru−CoP/CC) with a strong BIEF with the guidance of density functional theory (DFT) calculations. Impressively, despite its unsatisfactory activity at 10 mA cm−2 (overpotential of 44 mV), Ru−CoP/CC exhibited better activity (357 mV) than the benchmark Pt/C catalyst (505 mV) at 1 A cm−2. Experimental and theoretical studies revealed that strong hydrogen adsorption on the interfacial Ru atoms created a high energy barrier for hydrogen desorption and spillover, resulting in unsatisfactory activity at low current densities. However, as the electrode potential became more negative (i.e. the current density increased), the barrier for hydrogen spillover from the interfacial Ru to the Co site, which had near‐zero hydrogen adsorption energy, significantly decreased, thus greatly accelerating the whole alkaline HER process. This explains why the activity of Ru−CoP is relatively susceptible to the electrode potential compared to Pt/C. [ABSTRACT FROM AUTHOR]

Even though grain boundaries (GBs) have been previously employed to increase the number of active catalytic sites or tune the binding energies of reaction intermediates for promoting electrocatalytic reactions, the effect of GBs on the tailoring of the local chemical environment on the catalyst surface has not been clarified thus far. In this study, a GBs‐enriched iridium (GB−Ir) was synthesized and examined for the alkaline hydrogen evolution reaction (HER). Operando Raman spectroscopy and density functional theory (DFT) calculations revealed that a local acid‐like environment with H3O+ intermediates was created in the GBs region owing to the electron‐enriched surface Ir atoms at the GBs. The H3O+ intermediates lowered the energy barrier for water dissociation and provided enough hydrogen proton to promote the generation of hydrogen spillover from the sites at the GBs to the sites away from the GBs, thus synergistically enhancing the hydrogen evolution activity. Notably, the GB−Ir catalyst exhibited a high alkaline HER activity (10 mV @ 10 mA cm−2, 20 mV dec−1). We believe that our findings will promote further research on GBs and the surface science of electrochemical reactions. [ABSTRACT FROM AUTHOR]

Simultaneous optimization of the energy level of water dissociation, hydrogen and hydroxide desorption is the key to achieving fast kinetics for the alkaline hydrogen evolution reaction (HER). Herein, the well‐dispersed Ru clusters on the surface of amorphous/crystalline CeO2‐δ (Ru/ac‐CeO2‐δ) is demonstrated to be an excellent electrocatalyst for significantly boosting the alkaline HER kinetics owing to the presence of unique oxygen vacancy (VO) and Ru Lewis acid–base pairs (LABPs). The representative Ru/ac‐CeO2‐δ exhibits an outstanding mass activity of 7180 mA mgRu−1 that is approximately 9 times higher than that of commercial Pt/C at the potential of −0.1 V (V vs RHE) and an extremely low overpotential of 21.2 mV at a geometric current density of 10 mA cm−2. Experimental and theoretical studies reveal that the VO as Lewis acid sites facilitate the adsorption of H2O and cleavage of H‐OH bonds, meanwhile, the weak Lewis basic Ru clusters favor for the hydrogen desorption. Importantly, the desorption of OH from VO sites is accelerated via a water‐assisted proton exchange pathway, and thus boost the kinetics of alkaline HER. This study sheds new light on the design of high‐efficiency electrocatalysts with LABPs for the enhanced alkaline HER. [ABSTRACT FROM AUTHOR]

Here,nonprecious high‐entropy chalcogenide glasses (N‐HECGs) consisting of Co, Fe, Ni, Mo, W, and Te are demonstrated in a first demonstration of acidic oxygen evolution reaction (OER). N‐HECGs electrocatalysts with high activity and stability are synthesized using a hierarchical hybrid approach based on a combination of electrochemical deposition and tellurization process. The as‐prepared CoFeNiMoWTe N‐HECGs electrocatalysts exhibit an amorphous, porous structure of arrayed nanosheets with abundant active sites and the increased valence states of metal cations due to the incorporated non‐metallic Te, enabling the enhancement of glass forming ability and the valence states of metal elements. Thanks to the combination of their unique geometrical and chemical structure, as well as high configuration entropy nature and high corrosion‐resistance ability, the resultant CoFeNiMoWTe N‐HECGs exhibit excellent acidic OER catalytic performance with a superior overpotential of 373 mV and outstanding stability of 100 h at the current density of 10 mA cm−2 in 0.5 m H2SO4. Moreover, the CoFeNiMoWTe‐based proton exchange membrane water electrolyzer is demonstrated to require a cell voltage of 1.81 V at 70 °C to obtain the practically high current density of 1 A cm−2, and exhibits remarkably long‐term stability for 100 h with small potential degradation of only 30 mV. [ABSTRACT FROM AUTHOR]

Hydrogen energy is regarded as an auspicious future substitute to replace fossil fuels, due to its environmentally friendly characteristics and high energy density. In the pursuit of clean hydrogen production, there has been a significant focus on the advancement of effective electrocatalysts for the process of water splitting. Although noble metals like Pt, Ru, Pd and Ir are superb electrocatalysts for the hydrogen evolution reaction (HER), they have limitations for large-scale applications, mainly high cost and low abundance. As a result, non-precious transition metals have emerged as promising candidates to replace their more expensive counterparts in various applications. This review focuses on recently developed transition metal phosphides (TMPs) electrocatalysts for the HER in alkaline media due to the cooperative effect between the phosphorus and transition metals. Finally, we discuss the challenges of TMPs for HER. [ABSTRACT FROM AUTHOR]

The development of efficiently active and stable bifunctional noble‐metal‐based electrocatalysts toward overall water splitting is urgent and challenging. In this work, a rutile‐structured ruthenium‐zinc solid solution oxide with oxygen vacancies (Ru0.85Zn0.15O2‐δ) is developed by a simple molten salt method. With naturally abundant edges of ultrasmall nanoparticles clusters, Ru0.85Zn0.15O2‐δ requires ultralow overpotentials, 190 mV for acidic oxygen evolution reaction (OER) and 14 mV for alkaline hydrogen evolution reaction (HER), to reach 10 mA cm−2. Moreover, it shows superior activity and durability for overall water splitting in different electrolytes. Experimental characterizations and density functional theory calculations indicate that the incorporation of Zn and oxygen vacancies can optimize the electronic structure of RuO2 by charge redistribution, which dramatically suppresses the generation of soluble Rux>4 and allows optimized adsorption energies of oxygen intermediates for OER. Meanwhile, the incorporation of Zn can distort local structure to activate the dangling O atoms on the distorted Ru0.85Zn0.15O2‐δ as proton acceptors, which firmly bonds the H atom in H2O* to stabilize the H2O and considerably improves the HER activity. [ABSTRACT FROM AUTHOR]

Metal single‐atom (SA) catalysts have attracted immense attention due to the high catalytic efficiency given by the desired coordination environment of each metal atom. Yet, engineering the local electronic structure of SAs and multi‐atoms (MAs) still remains a challenge. Herein, an atomically dispersed catalyst comprised of Pt SAs, Pt‐Pt/V dual‐atoms, and small clusters supported on a vanadium and nitrogen co‐doped carbon (VNC) (denoted as Pt@VNC) surface is synthesized. In the Pt@VNC, both V and Pt atoms are evenly distributed on the surface of N‐doped carbon, while a few Pt atoms are linked to other Pt atoms via V, forming Pt clusters. The coordination structures of Pt atoms are modulated upon introducing atomically dispersed V sites (which generate small‐sized Pt clusters) and V2O5 clusters, showing extraordinary activity for the hydrogen evolution reaction (HER). Benefiting from the low charge transfer resistance, i.e., fast reaction kinetics, due to the synergistic effect of SAs and clusters, the Pt@VNC demonstrates superior catalytic efficiency and robust durability for the HER. It requires an overpotential of only 5 mV at a current density of 10 mA cm−2 and shows 15 times larger mass activity than the commercial 20 wt.% Pt/C catalyst. This novel catalyst‐design strategy paves a new way for maximizing catalytic efficiency by optimizing the coordination structure of metal atoms. [ABSTRACT FROM AUTHOR]

Reducing the particle sizes of transition metals [TMs] and avoiding their aggregation are crucial for increasing the TMs atom utilization and enhancing their industrial potential. However, it is still challenging to achieve uniform distributed and density-controlled TMs nanoclusters [NCs] under high temperatures due to the strong interatomic metallic bonds and high surface energy ofNCs. Herein, a series ofTMs NCs with controllable density and nitrogen-modulated surface are prepared with the assistance of a selected covalent organic polymer [COP], which can provide continuous anchoring sites and size-limited skeletons. The prepared Ir NCs show superior hydrogen evolution reaction [HER] and oxygen evolution reaction [OER] activities than commercial Pt/C and Ir/C in both acid and alkaline media. In particular, the as-prepared Ir NCs exhibit remarkable full water splitting performance, reaching a current density of 10 mA cm-2 at ultralow overpotentials of 1.42 and 1.43 V in alkaline and acidic electrolyte, respectively. The excellent electrocatalytic activities are attributed to the increased surface atom utilization and the improved intrinsic activity ofIr NCs. More importantly, the Ir NCs catalyst shows superior long-term stability due to the strong interaction between Ir NCs and the N-doped carbon layer. [ABSTRACT FROM AUTHOR]

The development of an efficient pH‐universal hydrogen evolution reaction (HER) electrocatalyst is essential for practical hydrogen production. Here, an efficient and stable pH‐universal HER electrocatalyst composed of the strongly coupled 2D NiCo2S4 and 2D ReS2 nanosheets (NiCo2S4/ReS2) is demonstrated. The NiCo2S4/ReS2 2D–2D nanocomposite is directly grown on the surface of the carbon cloth substrate, which exhibits excellent HER performance with overpotentials of 85 and 126 mV at a current density of 10 mA cm−2 and Tafel slopes of 78.3 and 67.8 mV dec−1 under both alkaline and acidic conditions, respectively. Theoretical and experimental characterizations reveal that the chemical coupling between NiCo2S4 and ReS2 layers induces electron transfer from Ni and Co to interfacial Re‐neighbored S atoms, enabling beneficial H atom adsorption and desorption for both acidic and alkaline HER. Simultaneously, an electron transfer‐induced spin‐crossover generates high‐spin interfacial Ni and Co atoms that promote water dissociation kinetics at the NiCo2S4/ReS2 interface, which is the origin of the superior alkaline HER activity. NiCo2S4/ReS2 also shows decent catalytic activity and long‐term durability for oxygen evolution reaction, and finally bifunctionality for overall water splitting. This study suggests a rational strategy to enhance water dissociation kinetics by inducing spin‐crossover via electron transfer. [ABSTRACT FROM AUTHOR]

Synergistic optimization of the elementary steps of water dissociation and hydrogen desorption for the hydrogen evolution reaction (HER) in alkaline media is a challenge. Herein, the Ru cluster anchored on a trace P‐doped defective TiO2 substrate (Ru/P‐TiO2) was synthesized as an electrocatalyst for the HER; it exhibited a commercial Pt/C‐like geometric activity and an excellent mass activity of 9984.3 mA mgRu−1 at −0.05 V vs. RHE, which is 34.3 and 18.7 times higher than that of Pt/C and Ru/TiO2, respectively. Experimental and theoretical studies indicated that using a rutile‐TiO2‐crystal‐phase substrate enhanced the HER activity more than the anatase phase. Rich surface oxygen vacancies on rutile‐TiO2 facilitated the adsorption and dissociation of water, while the partial substitution of Ti4+ with P5+ enhanced H2 generation by facilitating hydrogen spillover from the Ru site to the surface P site, synergistically enhancing the HER activity. [ABSTRACT FROM AUTHOR]

Synergistic optimization of the elementary steps of water dissociation and hydrogen desorption for the hydrogen evolution reaction (HER) in alkaline media is a challenge. Herein, the Ru cluster anchored on a trace P‐doped defective TiO2 substrate (Ru/P‐TiO2) was synthesized as an electrocatalyst for the HER; it exhibited a commercial Pt/C‐like geometric activity and an excellent mass activity of 9984.3 mA mgRu−1 at −0.05 V vs. RHE, which is 34.3 and 18.7 times higher than that of Pt/C and Ru/TiO2, respectively. Experimental and theoretical studies indicated that using a rutile‐TiO2‐crystal‐phase substrate enhanced the HER activity more than the anatase phase. Rich surface oxygen vacancies on rutile‐TiO2 facilitated the adsorption and dissociation of water, while the partial substitution of Ti4+ with P5+ enhanced H2 generation by facilitating hydrogen spillover from the Ru site to the surface P site, synergistically enhancing the HER activity. [ABSTRACT FROM AUTHOR]

Ru nanoparticles have been demonstrated to be highly active electrocatalysts for the hydrogen evolution reaction (HER). At present, most of Ru nanoparticles-based HER electrocatalysts with high activity are supported by heteroatom-doped carbon substrates. Few metal oxides with large band gap (more than 5 eV) as the substrates of Ru nanoparticles are employed for the HER. By using large band gap metal oxides substrates, we can distinguish the contribution of Ru nanoparticles from the substrates. Here, a highly efficient Ru/HfO2 composite is developed by tuning numbers of Ru-O-Hf bonds and oxygen vacancies, resulting in a 20-fold enhancement in mass activity over commercial Pt/C in an alkaline medium. Density functional theory (DFT) calculations reveal that strong metal-support interaction via Ru-O-Hf bonds and the oxygen vacancies in the supported Ru samples synergistically lower the energy barrier for water dissociation to improve catalytic activities. Although ruthenium nanomaterials have proven to be effective catalysts for H2 evolution, there is still room for activity improvements. Here, authors develop an efficient Ru/HfO2 electrocatalyst with tuned Ru-O-Hf bonds and oxygen vacancies that shows high activities for alkaline H2 evolution. [ABSTRACT FROM AUTHOR]

Two‐dimensional metal dichalcogenides have been evidenced as potential electrocatalysts for hydrogen evolution reaction (HER); however, their application is limited by a poor oxygen evolution reaction (OER) activity due to insufficient number/types of multi‐integrated active sites. In this study, we report a novel bifunctional catalyst developed by simultaneous engineering of single nickel atoms (NiSA) and nickel phosphate clusters (NiPi) to synergistically trigger surface‐functionalized MoS2 nanosheets (NSs) resulting in high reactivities for both HER and OER. The NiSA‐NiPi/MoS2 NSs material exhibits a fairly Pt‐like HER behavior with an overpotential of 94.0 mV and a small OER overpotential of 314.0 mV to reach 10 mA cm−2 in freshwater containing 1.0 M KOH. Experimental results of the catalyst are well supported by theoretical study, which reveals the significant modulation of electronic structure and enrichment of electroactive site number/types with their reasonably adjusted free adsorption energy. For evaluating practicability, the NiSA‐NiPi/MoS2 NSs‐based electrolyzer delivers effective operation voltage of 1.62, 1.52, and 1.66 V at 10 mA cm−2 and superior long‐term stability as compared to Pt/C//RuO2 system in freshwater, mimic seawater, and natural seawater, respectively. The present study indicates that the catalyst is a promising candidate for the practical production of green hydrogen via water electrolysis. [ABSTRACT FROM AUTHOR]

NiFe‐based hydroxides are considered as promising nonprecious catalysts for water oxidation due to their low cost and easy preparation. However, the rational design of NiFe‐based electrocatalysts remains a great challenge to address the sluggish reaction kinetics and severe deactivation problems for oxygen evolution reaction (OER). Here, the authors report a facile approach to fabricate an amorphous Ce‐doped NiFe hydroxide catalyst, which enables high activity and outstanding stability toward OER in alkaline media. The overpotential of electrodeposited amorphous Ce‐doped NiFe is only 195 mV at 10 mA cm−2. Meanwhile, the durability of the amorphous Ce‐doped NiFe is maintained for 300 h at 100 mA cm−2. The comprehensive characterization results reveal that the improved electrochemical performance of the amorphous Ce‐doped NiFe catalyst is originated from the favorable oxidation transition of active sites enabled by Ce‐doping. It is a very good strategy to introduce highly oxidized state ions to regulate the NiFe‐based catalyst to improve the catalytic activity and stability. [ABSTRACT FROM AUTHOR]

Rational design of efficient hydrogen evolution reaction (HER) electrocatalysts for mass production of hydrogen via electrochemical water splitting is a challenging but pressing task. Herein, an in situ dual doping engineering from phosphomolybdic acid encapsulated within the bimetallic metal‐organic‐frameworks strategy to synthesize P,Mo dual doped Ru ultrasmall nanoparticles embedded in P‐doped porous carbon (P,Mo‐Ru@PC) for efficient HER is proposed. As a result, P,Mo‐Ru@PC achieves a low overpotential of 21 at 10 mA cm−2, low Tafel slopes of 21.7 mV dec−1, and a mass activity about 22 times greater than that of commercial 20 wt% Pt/C in alkaline media. First principle calculations demonstrate that introducing Mo and P atoms into Ru lattices triggers the in situ electron donation from Ru to Mo and P and consequently reduces the energy barrier for the HER. [ABSTRACT FROM AUTHOR]

Hydrogen generation by electrolysis of water in an alkaline solution is a promising technology for clean hydrogen energy. Amorphous materials show much better performance than their crystalline counterparts. However, it is still challenging to design amorphous metal materials. Here, a series of amorphous transition metal nanoparticles (NPs) is successfully synthesized using a twisted covalent organic network (CON) that can provide twisted carbon layers as well as asymmetrically distributed nitrogen. With the fixed monomer pore, a low loading amount of RuCl3 results in amorphous‐only Ru nanoclusters (NCs, 1.5 nm), while a high content of RuCl3 leads to crystalline dominant Ru NPs (3 nm). The mixed phased Ru‐CON catalyst for the hydrogen evolution reaction (HER) shows extremely low overpotential at 10 mA cm–2 (12.8 mV in 1.0 m KOH) and superior stability (after 100 h test, current loss 5.3% at 75 mA cm–2). More importantly, amorphous‐only Ru‐CON with smaller Ru NCs shows much better mass activity and considerable stability compared to mixed‐phase Ru‐CON materials since amorphous Ru NPs can provide more active sites than in their crystalline state. With this strategy, amorphous Fe NPs and Ir NPs are successfully prepared for extended applications, and the HER activities are reported. [ABSTRACT FROM AUTHOR]

Single-atom-catalysts (SACs) afford a fascinating activity with respect to other nanomaterials for hydrogen evolution reaction (HER), yet the simplicity of single-atom center limits its further modification and utilization. Obtaining bimetallic single-atom-dimer (SAD) structures can reform the electronic structure of SACs with added atomic-level synergistic effect, further improving HER kinetics beyond SACs. However, the synthesis and identification of such SAD structure remains conceptually challenging. Herein, systematic first-principle screening reveals that the synergistic interaction at the NiCo-SAD atomic interface can upshift the d-band center, thereby, facilitate rapid water-dissociation and optimal proton adsorption, accelerating alkaline/acidic HER kinetics. Inspired by theoretical predictions, we develop a facile strategy to obtain NiCo-SAD on N-doped carbon (NiCo-SAD-NC) via in-situ trapping of metal ions followed by pyrolysis with precisely controlled N-moieties. X-ray absorption spectroscopy indicates the emergence of Ni-Co coordination at the atomic-level. The obtained NiCo-SAD-NC exhibits exceptional pH-universal HER-activity, demanding only 54.7 and 61 mV overpotentials at −10 mA cm−2 in acidic and alkaline media, respectively. This work provides a facile synthetic strategy for SAD catalysts and sheds light on the fundamentals of structure-activity relationships for future applications. While single, dispersed atoms enable efficient atomic utilization, controllably preparing single-atom dimers remains challenging. Here, authors prepare nickel-cobalt single-atom dimers as high-performance pH-universal H2 evolution electrocatalysts. [ABSTRACT FROM AUTHOR]

To develop effective electrocatalytic splitting of acidic water, which is a key reaction for renewable energy conversion, the fundamental understanding of sluggish/destructive mechanism of the oxygen evolution reaction (OER) is essential. Through investigating atom/proton/electron transfers in the OER, the distinctive acid–base (AB) and direct‐coupling (DC) lattice oxygen mechanisms (LOMs) and adsorbates evolution mechanism (AEM) are elucidated, depending on the surface‐defect engineering condition. The designed catalysts are composed of a compressed metallic Ru‐core and oxidized Ru‐shell with Ni single atoms (SAs). The catalyst synthesized with hot acid treatment selectively follows AB‐LOM, exhibiting simultaneously enhanced activity and stability. It produces a current density of 10/100 mA cm−2 at a low overpotential of 184/229 mV and sustains water oxidation at a high current density of up to 20 mA cm−2 over ≈200 h in strongly acidic media. [ABSTRACT FROM AUTHOR]

Facilitating the dissociation of water and desorption of hydrogen are both crucial challenges for improving the hydrogen evolution reaction (HER) in alkaline media. Herein, we report the synthesis of heterostructure of Ru2P/WO3@NPC (N, P co‐doped carbon) by a simple hydrothermal reaction using ruthenium and tungsten salts as precursors, followed by pyrolyzing under an Ar atmosphere. The Ru2P/WO3@NPC electrocatalyst exhibits an outstanding HER activity with an overpotential of 15 mV at a current density of 10 mA cm−2 and excellent durability in a 1.0 M KOH solution, outperforming state‐of‐the‐art Pt/C and most reported electrocatalysts. Experimental results combined with density functional calculations reveal that the electron density redistribution in Ru2P/WO3@NPC is achieved by electron transfer from NPC to Ru2P/WO3 and from Ru2P to WO3, which directly promotes the dissociation of water on W sites in WO3 and desorption of hydrogen on Ru sites in Ru2P. [ABSTRACT FROM AUTHOR]

Designing a facile strategy to access active and atomically dispersed metallic catalysts are highly challenging for single atom catalysts (SACs). Herein, a simple and fast approach is demonstrated to construct Pt catalysts with single atoms in large quantity via ball milling Pt precursor and N‐doped carbon support (K2PtCl4@NC‐M; M denotes ball‐milling). The as‐prepared K2PtCl4@NC‐M only requires a low overpotential of 11 mV and exhibits 17‐fold enhanced mass activity for the electrochemical hydrogen evolution compared to commercial 20 wt% Pt/C. The superior hydrogen evolution reaction (HER) catalytic activity of K2PtCl4@NC‐M can be attributed to the generation of Pt single atoms, which improves the utilization efficiency of Pt atoms and the introduction of Pt‐N2C2 active sites with near‐zero hydrogen adsorption energy. This viable ball milling method is found to be universally applicable to the fabrication of other single metal atoms, for example, rhodium and ruthenium (such as Mt‐N2C2, where Mt denotes single metal atom). This strategy also provides a promising and practical avenue toward large‐scale energy storage and conversion application. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) along with hydrogen evolution reaction (HER) have been considered critical processes for electrochemical energy conversion and storage through metal-air battery, fuel cell, and water electrolyzer technologies. Here, a new class of multifunctional electrocatalysts consisting of dominant metallic Ni or Co with small fraction of their oxides anchored onto nitrogen-doped reduced graphene oxide (rGO) including Co-CoO/N-rGO and Ni-NiO/N-rGO are prepared via a pyrolysis of graphene oxide and cobalt or nickel salts. Ni-NiO/N-rGO shows the higher electrocatalytic activity for the OER in 0.1 m KOH with a low overpotential of 0.24 V at a current density of 10 mA cm−2, which is superior to that of the commercial IrO2. In addition, it exhibits remarkable activity for the HER, demonstrating a low overpotential of 0.16 V at a current density of 20 mA cm−2 in 1.0 m KOH. Apart from similar HER activity to the Ni-based catalyst, Co-CoO/N-rGO displays the higher activity for the ORR, comparable to Pt/C in zinc-air batteries. This work provides a new avenue for the development of multifunctional electrocatalysts with optimal catalytic activity by varying transition metals (Ni or Co) for these highly demanded electrochemical energy technologies. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) electrocatalytic activities normalized to electrochemically active surface area (ECSA) were systematically evaluated and correlated with its composition (i.e., Mo content up to 26 at. %), crystal structure (i.e., face-centered cubic (fcc) to orthorhombic phase and the mixed phases with different phase ratios), and crystallinity. The electrodeposited with mixed phases exhibited highest ECSA (up to 228 cm2 per 1 cm2 geometric surface area) compared to deposits with single phase, which serves as the dominant factor to enhance exchange current density and overpotential. Low overpotentials per ECSA were observed with Mo content of 5.16 at% (fcc) and 24.1 at% (mixed phases). After normalizing with ESCA, The Tafel slope and exchange current density were indifference with Mo content, crystal phase, and grain size. The metallic Ni–Mo thin films have low mixed potential and overpotential at 10 mA/cm2 of 20 mV and 120 mV, respectively. • Ni–Mo with different composition, and crystal structure were electrodeposited. • Mixed crystal phases resulted in highest electrochemically active surface area. • Mixed phases Ni–Mo electrodeposits also show to enhance exchange current density. [ABSTRACT FROM AUTHOR]

Hydrogen gas (H2) is being intensively proposed as a next-generation clean energy owing to the depletion of fossil fuels. Electrochemical water splitting is one of the most promising processes for hydrogen production. Furthermore, many efforts focusing on electrochemical water splitting have been made to develop low-cost, electrochemically active, and stable catalysts for efficient hydrogen production. MoS2 has emerged as an attractive material for developing catalysts for the hydrogen evolution reaction (HER). Hence, in this study, we design hierarchically ordinated two-dimensional (2D) MoS2 nanosheets on three-dimensional (3D) reduced graphene oxide (rGO) (H-2D/3D-MoS2-rGO) aerogel structures as a new class of electrocatalysts for the HER. We use the one-pot hydrothermal synthesis route for developing high-performance electroactive materials for the HER. The as-prepared H-2D/3D-MoS2-rGO contains a unique 3D hierarchical structure providing large surface areas owing to the 3D porous networks of rGO and more active sites owing to the many edge sites in the MoS2 nanosheets. In addition, the H-2D/3D-MoS2-rGO structure exhibits remarkable electrochemical properties during the HER. It shows a lower overpotential than pure MoS2 and excellent electrochemical stability owing to the large number of active sites (highly exposed edge sites) and high electrical conductivity from the rGO structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • P-doped graphene quantum dots were synthesized with different P-C bond configurations via simple hydrothermal process. • The PGQD3/GH composite demonstrated excellent photocatalytic hydrogen production of 20.47 mmol·g−1·h−1 in seawater splitting. • The PGQD3/GH composite performs superior bifunctional electrochemical activities of HER and OER. • The seawater electrolysis cell using PGQD3/GH composite delivers small overall voltage with excellent stability. Designing metal-free catalyst with outstanding activity for both photocatalytic and electrocatalytic seawater splitting is highly demand and still remained challenge. This work demonstrates the synthesis of P-doped graphene quantum dots (PGQDs) containing different P-configuration bonding of PC 3 , PO 4 and PO 3 via synthesis temperature controlled simple hydrothermal process. Specifically, PGQDs having PC 3 -bonds (PGQD3) shows effectively tunable electronic structure, significant enhancing visible light absorption, then their hybrid composite with graphene hydrogel (PGQD3/GH) is prepared. The PGQD3/GH composite possesses excellent photocatalytic hydrogen production with yield of 20.47 mmol·g−1·h−1 in seawater splitting. Furthermore, the PGQD3/GH composite performs superior electrochemical activities of hydrogen evolution reaction (HER) toward seawater with an overpontetial of 41 mV at 10 mA·cm−2 as well as oxygen evolution reaction (OER) with 262 mV at 10 mA·cm−2. In seawater electrolysis cell, the PGQD3/GH composite delivers small overall voltage of 1.62 V to obtain high current density of 500 mA·cm−2 with excellent stability for 1000 h continuous operation, outperforming the commercial Pt/C and IrO 2. This work demonstrates the role of PC 3 -bond in modulating the band gap and active site for photocatalytic and electrocatalytic seawater splitting reaction that may provide new idea for developing porous non-metal all-carbon catalyst for seawater splitting by both photocatalysis and electrocatalysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Facile synthesis of Ni 2 P supported on nitrogen doped-carbon (Ni 2 P@N-C). • Bifunctional activity for ammonia oxidation (AOR) and hydrogen evolution (HER). • Ni 2 P@N-C electrocatalyst exhibits about 78% decomposition of ammonia. • The hydrogen generation is estimated to be 2.144 mmol (H2) /mol (NH3) h cm2. • A low energy consumption rate of 8.611 KWH Kg (H2) −1 was achieved. Ammonia, as an efficient hydrogen carrier, is emerging as an alternative energy resource to replace fossil fuels in the carbon–neutral era. Hydrogen production by water electrolysis seeks a lower potential dependent anodic reaction to overcome its energy-inefficiency that originates from the high potential anodic oxygen evolution reaction (OER). In this work, nickel phosphide supported on nitrogen doped-carbon (Ni 2 P@N-C) was prepared by one-pot synthesis for the bifunctional activity of hydrogen evolution (HER) and ammonia oxidation (AOR) reactions. The Ni 2 P@N-C electrocatalyst exhibits about 78% decomposition of ammonia compared to the initial concentration. The amount of hydrogen generated in a 0.5 M ammonia environment for 30 min is about 2.144 mmol (H 2) / mol (N H 3) h cm2. The fabricated ammonia electrolysis cell demonstrates a comparatively low energy consumption rate of 8.611 KWHkg (H 2) −1. Thus, engineering a bifunctional electrocatalyst for a low potential anode oxidation reaction and the cathodic HER is a promising strategy to fabricate an energy efficient electrolysis cell for hydrogen production with a low cell potential requirement. [ABSTRACT FROM AUTHOR]

Synergistic optimization of the elementary steps of water dissociation and hydrogen desorption for the hydrogen evolution reaction (HER) in alkaline media is a challenge. Herein, the Ru cluster anchored on a trace P‐doped defective TiO2 substrate (Ru/P‐TiO2) was synthesized as an electrocatalyst for the HER; it exhibited a commercial Pt/C‐like geometric activity and an excellent mass activity of 9984.3 mA mgRu−1 at −0.05 V vs. RHE, which is 34.3 and 18.7 times higher than that of Pt/C and Ru/TiO2, respectively. Experimental and theoretical studies indicated that using a rutile‐TiO2‐crystal‐phase substrate enhanced the HER activity more than the anatase phase. Rich surface oxygen vacancies on rutile‐TiO2 facilitated the adsorption and dissociation of water, while the partial substitution of Ti4+ with P5+ enhanced H2 generation by facilitating hydrogen spillover from the Ru site to the surface P site, synergistically enhancing the HER activity. [ABSTRACT FROM AUTHOR]

Synergistic optimization of the elementary steps of water dissociation and hydrogen desorption for the hydrogen evolution reaction (HER) in alkaline media is a challenge. Herein, the Ru cluster anchored on a trace P‐doped defective TiO2 substrate (Ru/P‐TiO2) was synthesized as an electrocatalyst for the HER; it exhibited a commercial Pt/C‐like geometric activity and an excellent mass activity of 9984.3 mA mgRu−1 at −0.05 V vs. RHE, which is 34.3 and 18.7 times higher than that of Pt/C and Ru/TiO2, respectively. Experimental and theoretical studies indicated that using a rutile‐TiO2‐crystal‐phase substrate enhanced the HER activity more than the anatase phase. Rich surface oxygen vacancies on rutile‐TiO2 facilitated the adsorption and dissociation of water, while the partial substitution of Ti4+ with P5+ enhanced H2 generation by facilitating hydrogen spillover from the Ru site to the surface P site, synergistically enhancing the HER activity. [ABSTRACT FROM AUTHOR]

Designing highly efficient Pt-free electrocatalysts with low overpotential for the alkaline hydrogen evolution reaction (HER) remains a significant challenge. In this paper, we successfully construct Ru-incorporated oxygen-vacancy-enriched MoO 2 nanosheets (Ru/MoO 2−x) for the HER through a "one stone two birds" strategy. This strategy can solve two urgent problems simultaneously, the intrinsic electrochemical activity of original MoO 2 is far from satisfactory and the H 2 O adsorption/dissociation abilities of Ru are weak. Specifically, the oxygen-vacancy-enriched MoO 3 serves as an excellent platform for anchoring and trapping Ru ions. In-depth analyses indicate that the incorporation of Ru nanoclusters induces transition from MoO 3 to MoO 2 , generates oxygen vacancies, and creates Ru-O-Mo sites. The synergistic effect of Ru nanoclusters, Ru-O-Mo sites and oxygen-vacancy-enriched MoO 2 will endow the obtained catalyst excellent electrocatalytic activity. In particular, the optimal Ru/MoO 2−x electrocatalyst delivered a low overpotential of 29 mV at 10 mA cm−2 in a basic electrolyte. The incorporated Ru nanoclusters induce the transition from MoO 3 to MoO 2 , generation of oxygen vacancies, and creation of Ru-O-Mo sites simultaneously, endowing the synthesized catalyst excellent performance towards alkaline HER. [Display omitted] • A"one stone two birds" strategy is adopted. • The incorporation of Ru induces transition from MoO 3 to MoO 2. • The introduction of Ru promotes to generate oxygen vacancy and create Ru-O-Mo site. • The optimal catalyst exhibits high intrinsic activity for alkaline HER. [ABSTRACT FROM AUTHOR]

Fe N C catalyst containing abundant atomic Fe-N x sites is synthesized using a MgCl 2 -assisted synthesis approach. The catalyst delivered an excellent oxygen reduction activity in alkaline and acidic electrolytes with outstanding stability. [Display omitted] • Highly active Fe N C catalyst is synthesized by a simplified salt-assisted approach. • Only a single heat-treatment step is employed to produce a highly active catalyst. • The synthesized Fe N C catalyst consists of atomic Fe-N x sites exclusively. • Optimized catalyst delivers excellent ORR activity in acidic and alkaline media. Nitrogen-doped porous carbons containing atomically dispersed iron are prime candidates for substituting platinum-based catalysts for oxygen reduction reaction (ORR) in fuel cells. These carbon catalysts are classically synthesized via complicated routes involving multiple heat-treatment steps to form the desired Fe-N x sites. We herein developed a highly active Fe N C catalyst comprising of exclusive Fe-N x sites by a simplified solid-state synthesis protocol involving only a single heat-treatment. Imidazole is pyrolyzed in the presence of an inorganic salt-melt resulting in highly porous carbon sheets decorated with abundant Fe-N x centers, which yielded a high density of electrochemically accessible active sites (1.36 × 1019 sites g−1) as determined by the in situ nitrite stripping technique. The optimized catalyst delivered a remarkable ORR activity with a half-wave potential (E 1/2) of 0.905 V RHE in alkaline electrolyte surpassing the benchmark Pt catalyst by 55 mV. In acidic electrolyte, an E 1/2 of 0.760 V RHE is achieved at a low loading level (0.29 mg cm−2). In PEMFC tests, a current density of 2.3 mA cm−2 is achieved at 0.90 V iR-free under H 2 –O 2 conditions, reflecting high kinetic activity of the optimized catalyst. [ABSTRACT FROM AUTHOR]

Doped carbon structures have been developed as non-precious metal catalysts for oxygen reduction reactions (ORR) in polymer electrolyte membrane fuel cells (PEMFCs). Among doped carbon structures, Fe- and N-doped carbon (Fe/N/C) nanostructured catalysts have received attention due to their catalytic activity, comparable to that of Pt, avoiding the use of critical raw materials. However, obviously, its durability is not yet neither fully understood nor comparable to that of traditional catalysts. In this study, we synthesized mesoporous F-doped Fe/N/C, which is a tri-doped carbon nanostructure, as a cathode catalyst for ORR. Tri-doped carbon catalysts with different amounts (x) of F (Fx-Fe/N/C) were prepared using Fe-5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphine iron(III) chloride and NH 4 F as the Fe/N- and F- doping sources, respectively, and Santa Barbara amorphous-15 as the template. Fx-Fe/N/C with an optimal F content exhibited excellent electrocatalytic performance for ORRs i.e. a high half-wave potential of 809 mV in 0.1 M HClO 4 solution, a maximum power density of 280 mW cm−2, and a high stability for 4000 min at 0.5 V, owing to the high proportion of FeN x and pyridinic N as active sites, strong C–F bonds, and hydrophobic surfaces. We synthesized mesoporous F-doped Fe/N/C, which is a tri-doped carbon nanostructure, as a cathode catalyst for ORR. Fx-Fe/N/C with an optimal F content exhibited excellent electrocatalytic activity and durability for ORRs owing to the high proportion of FeNx and pyridinic N as active sites, strong C–F bonds, and hydrophobic surfaces. [Display omitted] [ABSTRACT FROM AUTHOR]

Development of efficient and stable electrocatalysts for oxygen evolution reaction (OER) under acidic conditions is desirable goal for commercializing proton exchange membrane (PEM) water electroyzer. Herein, we report iridium-doped hydrogenated titanate (Ir–HTO) nanobelts as a promising catalyst with a low-Ir content for the acidic OER. Addition of low-Ir (∼ 3.36 at%) into the single-crystalline HTO nanobelts with large exposed {100} facets significantly boost catalytic activity and stability for OER under acidic conditions. The Ir-HTO outperforms the commercial benchmark IrO 2 catalyst; an overpotential for delivering 10 mA cm−2 current density was reduced to about 25% for the Ir-HTO. Moreover, the catalytic performance of Ir-HTO is positioned as the most efficient electrocatalyst for the acidic OER. An improved intrinsic catalytic activity and stability are also confirmed for the Ir-HTO through in-depth electrochemical characterizations. Therefore, our results suggest that low-Ir doped single-crystalline HTO nanobelts can be a promising catalyst for efficient and durable OER under acidic conditions. • We developed an Ir-doped catalyst for the acidic oxygen evolution reaction (OER). • Ir was incorporated into a H 2 Ti 3 O 7 nanobelts (Ir–HTO) with large exposed {100} facets. • The single-crystalline nature of HTO increased the active sites for the OER. • The Ir-HTO nanobelts have a low Ir content (about 3–4 wt%) at the atomic scale. • The Ir-HTO nanobelts have high catalytic activity and durability for acidic OER. [ABSTRACT FROM AUTHOR]

High-performance electrocatalysts have attracted growing interest because of their crucial roles in renewable energy technologies. In this study, the host, interlayer, and surface features of electrocatalytically-active 2D nanosheets (NSs) are systematically controlled with the synergetic combination of host−guest co-engineering and surface modification to develop a novel synthetic strategy for efficient electrocatalysts. Molecular-level control of interfacial electronic coupling and surface reactivity can be achieved by the self-assembly of MoS 2 /RuO 2 NS mixtures with variable-sized tetraalkylammonium cations and subsequent thermal aging. The resulting optimization of the operation mechanisms of restacked MoS 2 /RuO 2 NSs effectively improves the electrocatalyst functionality for hydrogen evolution reaction (HER). The extensive modifications of diverse structural and morphological parameters allow the elucidation of a linear correlation between electrochemical active surface area and HER overpotential. Systematic in-situ spectroscopic analyses clearly demonstrate the crucial role of enhanced Volmer−Tafel mechanism in improving the electrocatalytic activity via enhancement of proton adsorption and interfacial electron transfer. Promoted Volmer-Tafel process achieved by molecular-level control of host, interlayer, and surface features. [Display omitted] • Host–guest engineering and surface activation strategies are synergistically applied. • Interlayer coupling and surface activity of electrocatalyst nanosheets are optimized. • Volmer–Tafel process plays a crucial role in optimizing electrocatalyst performance. • Electrochemical active surface area acts as a main design factor for electrocatalyst. [ABSTRACT FROM AUTHOR]

The effect of basal plane oxygen functional groups of GO on the Co-N transition is investigated by tailoring the oxygen content and composition of oxygen functional groups on the basal plane of GO sheets. The high oxygen functional groups on the basal plane provide energetically favorable environments for Co-N formation. The hydrogen evolution reaction (HER) activities correlate to the amounts of Co-N sites. [Display omitted] • Effect of basal plane oxygen functional groups on Co-N transition is investigated. • The adsorption of cobalt ions and Co-N transition are investigated by XPS and XAFS. • The Co-N transition is facilitated by oxygen functional groups on the basal plane. • The HER catalytic activity is closely related to the amounts of Co-N sites. The designed synthesis of graphene oxide (GO) for the formation of nitrogen-coordinated atomic metal sites (M−N−C) is crucial for developing efficient M−N−C catalysts. Here, the effect of basal plane oxygen functional groups of GO on the adsorption of cobalt ions and their Co-N transition is investigated by tailoring the oxygen content and composition of oxygen functional groups on the basal plane of GO sheets. The tailor-made GO shows that the specific oxygen functional groups, such as hydroxyl, epoxy, and carbonyl groups, can be efficiently incorporated with formation of defected structures on the basal plane of GO sheets rather than their edge. The adsorption of cobalt ions on the GO sheets and their transition to the Co-N state are systematically investigated by XPS and XAFS analyses. Annealing temperature-controlled experiments reveal that the incorporation of nitrogen around cobalt atoms is facilitated by the increased number of oxygen functional groups on the basal plane rather than those on the edge of GO sheets, which provide energetically favorable environments for Co-N formation. The hydrogen evolution reaction (HER) activities of the resulting cobalt atom-immobilized and annealed GO (Co/GO x -T) catalysts correlate to the degree of Co-N saturation, while also demonstrating excellent HER catalytic durability. [ABSTRACT FROM AUTHOR]

Water electrolysis (WE) is an attractive advanced technology for the production of H 2. A key issue in the WE is to develop suitable catalysts for the oxygen evolution reaction (OER), where a relatively large energy loss occurs. The Ir-doped NiCo 2 O 4 catalysts exhibit the formation of a solid solution and a porous nanostructure. The oxygen vacancies formed by Ir doping can enhance the electrocatalytic activity for the OER owing to increased electrical conductivity and tunable adsorption energies of OH- and H 2 O. In comparison to IrO 2 as a representative OER catalyst, the Ir(10 at%) doped NiCo 2 O 4 catalyst (10-Ir-NCO) exhibits the better OER performance (overpotential of 303 mV at 10 mA cm−2) and its stability for 20,000 s. In addition, in the overall water splitting test, the 10-Ir-NCO || Pt/C exhibits the excellent OER activity (a low overpotential of 0.5 V at 100 mA cm−2) and stability (20 h at 50 mA cm−2). [Display omitted] • Ir-doped NiCo 2 O 4 catalysts were synthesized with various amounts of Ir dopant. • The catalysts exhibited a spinel structure consisting of NiCo 2 O 4 host and Ir dopant. • The catalyst exhibited the enhanced activity and stability for the OER compared to IrO 2. • The enhanced activity may result from the replacement of Ni and Co with Ir in octahedral sites. • The enhanced activity may be attributed to the oxygen vacancies. [ABSTRACT FROM AUTHOR]

• Highly active Co/Ru sites were designed via constructing Ru atom-modified Co 4 N-CoF 2. • The cooccurrence of F, N, Ru in Co neighborhood achieves optimized electronic state. • Ru atom-modified Co 4 N-CoF 2 exhibits superior hydrogen evolution reaction activity. D-band-center control engineering, particularly combining both cation and anion intercalations towards heterostructure formation with simultaneous usage of Ru, N as well as F species, for optimal electronic structure as efficient hydrogen evolution reaction (HER) catalysts remains a daunting challenge but critical for renewable-energy technologies. Herein, we lay emphasis on the design of active-site electronic structure based on d-band-center shift through the construction of Co 4 N-CoF 2 heterostructure coupled with Ru doping (Ru/Co 4 N-CoF 2). Solvothermal coordination reaction followed by annealing course causes cooccurrence of F, N, Ru in Co neighborhood. As-obtained Ru/Co 4 N-CoF 2 exhibits superior HER activity in alkaline electrolyte with overpotential as low as 53 mV to yield a current density of 10 mA cm−2 which is close to that of commercial Pt/C, outperforming many transition-metal-based catalysts recent-reported. Moreover, it still presents good durability with continuous operation of 22 h in 1.0 M KOH. Such excellent performance is ascribed to appropriate electron structure of Ru/Co 4 N-CoF 2 for optimized hydrogen binding abilities on Co/Ru sites as confirmed by synchrotron-based X-ray adsorption near-edge structure and X-ray photoelectron spectroscopies. This study not only establishes highly active electrocatalysts by impacting d-band center of active sites but also provides valuable insights into the synergistic-effect protocol of doping and heterostructure strategies for d-band-center shifting. [ABSTRACT FROM AUTHOR]

• Bimetal TMO supported carbon (CNT/Graphene) based electrocatalyst (NCGC) is synthesized via dry synthesis. • NCGC exhibited high electrochemical activity and good stability for both OER & HER. • NCGC provide low overpotentials of 290 and 214 mV at 10 mA cm−2 to drive the OER & HER, respectively. • NCGC offers reasonable electrochemical stable electrolysis performance over 60 h. The rational design of highly efficient bifunctional electrocatalysts for the oxygen and hydrogen evolution reactions is still an ongoing challenge. Herein, bimetallic transition metal oxide incorporated three-dimensional (3D) nitrogen-doped graphene/carbon nanotube (CNT) conductive matrix has been developed via dry synthesis and applied as a potential catalyst for the oxygen and hydrogen evolution reactions. The key features of the structure as well as its 3D network, nitrogen doping, and metal oxide formation were confirmed using various characterization techniques such as scanning electron and transmission electron microscopies, X-ray diffraction, and X-ray photoelectron spectroscopy. A nickel cobalt oxide-incorporated 3D nitrogen-doped graphene/CNT conductive matrix (NCGC) exhibits low overpotentials of 290 and 214 mV at 10 mA cm−2 to drive the oxygen and hydrogen evolution reactions, respectively. Furthermore, the NCGC electrocatalyst maintains a reasonably long-term water electrolysis performance over 20 h, thought to be as a result of an improvement in the activity and stability of NCGC through the synergetic effects of the bimetallic transition oxide and 3D nitrogen-doped graphene/CNT. The overall electrochemical activity and stability of the prepared NCGC make it a good economical substitute for commercial noble metal-based catalysts for use in renewable energy production. [ABSTRACT FROM AUTHOR]

It is of tremendous significance to develop effective bifunctional electrocatalysts for electrochemical water-splitting to generate sustainable hydrogen energy. Herein, a facile and scalable strategy is evolved to design N doped bamboo-like carbon nanotube decorated with tri-metal nanoparticles (Fe–Ni–Cr/NC) for overall water-splitting in alkaline electrolyte. Coupling effects between different metals and intimately contact with the carbon matrix endow the obtained nanomaterial possesses splendid catalytic activity and stability for cathodic HER, anodic OER and overall water-splitting in alkaline electrolyte. The obtained Fe–Ni–Cr/NC exhibits the best catalytic performance for HER (284 mV@10 mA cm−2) relative to Fe–Cr/NC (368 mV), Ni–Cr/NC (314 mV) and Fe–Ni/NC (324 mV). For OER, a small overpotential of 210 mV is needed to drive 10 mAcm−2 which is superior to IrO 2 (330 mV). Thus, the interactions between different metals act as paramount effects on promoting the catalytic activities. Benefiting from the outstanding catalytic performances for both HER and OER, the designed Fe–Ni–Cr/NC possesses splendid catalytic activity for overall water-splitting with a small potential of 1.64 V to deliver 10 mA cm−2. Moreover, the obtained nanomaterial also owns remarkable long-term stability in the measured electrolyte. Image 1 • A facile strategy is developed to prepare N-doped bamboo like carbon nanotubes coupled with Fe–Ni–Cr nanoparticles. • The obtained nanomaterial presents excellent catalytic performance for overall water-splitting in alkaline media. • The prepared electrocatalyst exhibits outstanding long-term stability. [ABSTRACT FROM AUTHOR]