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Crystallized Ruthenium (Ru) metal with high hydrogen production activity is extremely unstable. Herein, we report an efficient and durable hydrogen evolution reaction (HER) electrocatalyst Ru‐MC (mesoporous carbon) synthesized by a special method, in which Ru3+ is added after the formation of spherical MC, leading to only a small amount of Ru being embedded and the vast majority being evenly distributed on the MC surface. The dispersed Ru nanoparticles not only prevent them from aggregation to greatly improve their stability (both over 160 hours in acidic and alkaline solutions), but also provide outstanding intrinsic catalytic activity because oxygen regulates the electronic structure of Ru nanoparticles. The as‐synthesized catalyst only needs an overpotential of 27 and 40 mV to deliver 10 mA cm−2 in 1.0 M KOH and 0.5 M H2SO4. The present work provides guidance for the design of efficient and stable Ru‐based HER electrocatalysts used in a wide pH range. [ABSTRACT FROM AUTHOR]

Herein, a transition metal dissolution‐oxygen vacancy strategy, based on dissolution of highly oxidized transition metal species in alkaline electrolyte, was suggested to construct a high‐performance amorphous Co(OH)2/WOx (a‐CoW) catalyst for the oxygen evolution reaction (OER). The surface reconstruction of a‐CoW and its evolution were described by regulating oxygen vacancies. With continuous dissolution of W species, oxygen vacancies on the surface were generated rapidly, the surface reconstruction was promoted, and the OER performance was improved significantly. During the surface reconstruction, W species also played a role in electronic modulation for Co. Due to its rapid surface reconstruction, a‐CoW exhibited excellent OER performance in alkaline electrolyte with an overpotential of 208 mV at 10 mA cm−2 and had long‐term stability for at least 120 h. This work shows that the transition metal dissolution‐oxygen vacancy strategy is effective for preparation of high‐performance catalysts. [ABSTRACT FROM AUTHOR]

Preparing low-cost and metal-free catalysts with outstanding catalytic activity and high stability to replace noble metal catalysts is the current development trend. Herein, a facile and low-cost two-step carbonization is proposed for the preparation of N, S-codoped oxygen reduction reaction (ORR) electrocatalysts, PP350KOH800-S, from the biomass waste pomelo peel by introducing KOH and thiourea as activator. The prepared electrocatalysts have the high specific surface area and the hierarchical porous structure and exhibit excellent ORR catalytic activity with the half-wave potential of 0.87 V and the limiting diffusion current density of −7.2 mA cm−2 in alkaline media. The excellent ORR electrocatalytic activity largely depends on the large specific surface area, the porous structure, the high degree of defects, and the synergistic effect of nitrogen and sulfur atoms. The present work provides a reliable method for the preparation of cheap and effective electrocatalysts using biomass waste. [ABSTRACT FROM AUTHOR]

Synergistic effect in multi-component Ru-NiCo alloys for enhanced overall water splitting. The atoms of the three metal elements perform their respective duties and jointly promote the efficient electrocatalytic activity of the as-prepared catalysts. [Display omitted] • Two kinds of alloy catalysts were fabricated by a facile method. • Ru-NiCo 0.5 -600 °C||Ru-Ni 0.75 Co cell shows excellent activity and stability. • The roles of Ru, Ni and Co during the catalytic process were explained. • The synergistic effect of multi-component alloys was proposed. Understanding the synergistic mechanism of multi-component alloys is crucial and challenging for overall water splitting. Herein, Ru-NiCo 0.5 -600 °C and Ru-Ni 0.75 Co with excellent electrocatalytic activity are designed and synthesized. The Ru-NiCo 0.5 -600 °C alloy exhibits remarkable HER activity with an overpotential of 42, 77 and 93 mV at 10 mA cm−2 in alkaline, acidic and neutral conditions, and the Ru-Ni 0.75 Co electrocatalyst presents outstanding OER activity with an overpotential of 176 mV at 10 mA cm−2 in 1.0 M KOH. The Ru-NiCo 0.5 -600 °C ||Ru-Ni 0.75 Co cell requires only 1.48 and 1.69 V to reach 10 and 100 mA cm−2 towards overall water splitting. A series of experiments reveal that the strong electronic coupling among Ru, Ni and Co regulates the electronic structure and enhances the intrinsic catalytic activity and stability of the as-synthesized Ru-NiCo electrocatalysts. Systematic experimental and theoretical results prove that Ni atoms act as the active sites of dissociating water, while Ru and Co are respectively the active centers of proton and hydroxyl adsorption for HER and OER. Our work provides a new perspective for profoundly understanding the synergistic effect of multi-component alloys towards water splitting. [ABSTRACT FROM AUTHOR]

Urea is of great importance for the survival and development of mankind because of its advantages in effectively increasing crop yields. A novel carbon-supported indium-doped bismuth nanoparticles (Bi: 10 %In/C NPs) was prepared for the synthesis of urea via the co-activated reduction of nitrate and CO 2 with an average Faraday efficiency (FE) of 20.31 % and urea yield (R urea) of 606.38 μg mg−1 h−1. Interestingly, the In doped here not only serves as the active site, but also acts as an activator to stimulate the activity of Bi through electronic interaction, thus making Bi also the active site for the electrocatalytic C-N coupling reaction. Simultaneously, the key intermediates of the reaction are revealed to be *NH 2 and *CO. This work provides further insight into the role of indium in the electrocatalytic C-N coupling for the synthesis of urea, which gives a direction for thinking about the design and construction of subsequent highly efficient electrocatalysts. A novel catalyst based on carbon-supported In-doped Bi nanoparticles (Bi:10 % In/C NPs) was prepared for the co-activated reduction of nitrate and CO 2 for the synthesis of urea with average FE and urea yield of 20.31 % and 606.38 μg mg−1 h−1 at − 0.45 V vs. RHE. The key intermediates of the reaction are revealed to be *NH 2 and *CO. Interestingly, experimental results show that the doped In acts not only as the active site but also as an "activator", stimulating the activity of Bi through electronic interactions, thus making Bi also the active site for electrocatalytic C-N coupling reactions. [Display omitted] ● A bismuth-based catalyst well suited for the electrochemical synthesis of urea (FE: 20.31 %, R urea : 606.38 μg mg−1 h−1) was prepared by a simple room temperature reduction method based on the property of bismuth to inhibit competitive hydrogen evolution reactions. ● A strategy for the preparation of electrocatalysts for highly efficient urea synthesis using direct activation of bismuth by indium is proposed for the first time. ● Theindium in the prepared Bi:In/C not only directly participates in the synthesis of urea as the active site, but also acts as an activator to activate the inert bismuth, so that bismuth also becomes the active site of the C-N coupling reaction, thus greatly improving the efficiency and stability for the synthesis of urea. [ABSTRACT FROM AUTHOR]

Herein, a highly effective bifunctional water splitting catalyst with long-term durability, MoO 2 @CoN, was successfully constructed. As discovered, the MoO 2 /CoN interface formation resulted in the electron transfer from MoO 2 to CoN and the generation of high-valence Mo6+, inducing a strong electronic polarization at interfaces and stabilizing greatly the surface electronic structure, which significantly improved the bifunctional catalytic performance and long-term stability. In alkaline electrolytes, MoO 2 @CoN exhibited excellent bifunctional performance with quite low overpotentials of 59 mV for HER at 10 mA cm−2 and 227 mV for OER at 20 mA cm−2, respectively, and the catalysis sustained a constant current density for more than 500 h. Theoretical calculations confirmed that Co served as an active site rather than Mo, and its HER and OER activities were considerably improved by the strong electronic polarization at interfaces. This work is important for designing efficient bifunctional catalysts by means of strong interfacial coupling. [Display omitted] • Highly-efficient bifunctional catalyst with a long-time durability was constructed. • Efficient activity and durability are due to interface-induced polarization and Mo6+. • MoO 2 @CoN acquired an ultralow OER overpotential of 227 mV at 20 mA cm−2 in 1.0 M KOH. • Electrocatalysis maintained a steady current density for at least 500 h. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fabricating efficient and durable OER catalysts suitable for high current density. • Disclosing the synergy of in-situ formed adsorbates and surface-reconstructed interfaces. • Catalyst has an OER overpotential of 315 mV at 1 A·cm−2 and sustains 1 A·cm−2 for 100 h. Fabricating highly-efficient and long-time stable catalysts for water splitting under large current density is of great significance for the industrial production of hydrogen through water splitting. Herein, a heterointerface Fe 7 S 8 /NiS 2 catalyst was constructed and the impact of the interaction between in-situ generated SO 4 2− and reconstructed interface on its activity was evaluated. As shown, SO 4 2−, as an electron acceptor and electron bridge, greatly optimized the interface electron structure and enhanced the interface electron coupling via its interaction with the interface. Benefiting from this, the catalyst exhibited an excellent catalytic capacity at high current densities in alkaline electrolyte and only required overpotential of 281/315 mV for the OER to reach 500/1000 mA·cm−2, and sustained a stable current density of 1000 mA·cm−2 for 100 h. The experiments and DFT computations confirmed that the synergy of in-situ generated SO 4 2− and reconstructed FeOOH-NiOOH interfaces for Fe 7 S 8 /NiS 2 was responsible for its highly-performance catalytic activity and long-time durability. This work elucidates the synergistic effect of adsorbates and the heterointerfaces and has a reference value for constructing efficient and durable catalysts for water splitting. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high-performance Ru-Ni 3 S 2 /Ni x P y catalyst was fabricated. • Synergy of dopant and interface induced an ultrastrong electronic coupling. • Ultrastrong coupling effectively regulated the surface electronic structure. It is challenging to fabricate high-efficiency and low-cost bifunctional electrocatalysts for water splitting. Herein, a high-performance nickel-based catalyst, Ru-Ni 3 S 2 /Ni x P y , was constructed via heteroatom doping and interface engineering. The synergy of Ru-doping and sulfide-phosphide heterointerfaces induced the ultrastrong electronic coupling on the catalyst surface, which effectively regulated electronic densities of the catalyst, improved intrinsic catalytic activities, and resulted in the excellent HER and OER bifunctional performances. In alkaline medium, it only required the OER overpotential of 244 mV for the as-prepared Ru-Ni 3 S 2 /Ni x P y catalyst to achieve 100 mA∙cm−2 and the HER overpotential of 51 mV to reach 10 mA∙cm−2. And only a voltage of 1.46 V was required to generate 10 mA∙cm−2 in the Ru-Ni 3 S 2 /Ni x P y (+,-) cell. Furthermore, the as-prepared Ru-Ni 3 S 2 /Ni x P y catalyst exhibited a long-term durability for water splitting. The DFT calculations indicated that the ultrastrong electronic coupling was primarily attributed to the aggregation of electrons around heterointerfaces and the excellent catalytic performance was due to effectively adjusting the adsorption of intermediates on active sites. This work is helpful for developing an effective strategy to fabricate high-performance catalysts. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting remains a long way from large-scale practical application due to the fact that the catalytic efficiency cannot satisfy the requirement, and thus reasonable design catalyst is particularly essential. Herein, a heteroatom-doped heterogeneous interfacial catalyst (Fe-CoN/CoS 2) has been successfully synthesized by nitridation and sulfidation process for water electrolysis. Strikingly, an ultralow OER overpotential (154 mV) at 10 mA·cm-2 for OER is achieved. Meanwhile, Fe-CoN/CoS 2 is of low HER overpotentials of 72 and 39 mV to drive current density of 10 mA·cm-2 in alkaline and acid condition, respectively. Furthermore, the electrolytic cell assembled with Fe-CoN/CoS 2 drives a voltage of 1.48 V at 10 mA·cm-2. The doping of Fe can further reinforce the interaction of heterointerface between CoN and CoS 2 , resulting in the interfacial coupling enhancement. Density functional theory (DFT) calculations verify the Fe-doping can alter the electronic structure around the heterointerface and boosts the intrinsic catalytic activity, thus reduces the adsorption energy barriers about H* and oxygen-containing intermediates. This work provides a significant insight into the understanding of transition metal ion-doping heterointerface for facilitating the catalytic activity. [Display omitted] • A high-performance Fe-doping CoN/CoS 2 was constructed, which displayed an ultra-low OER overpotential 154 mV at 10 mA·cm-2. • The Fe-doping can further reinforce the interaction between CoN and CoS 2 , resulting in the interfacial coupling enhancement. • The dopant-induced interfacial coupling enhancement effect was confirmed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Efficient NO 3 – reduction to NH 3 was realized via incorporation of B into Cu. • Boron-induced electron localization greatly improved catalytic activity. • Incorporation of B effectively inhibited production of by-products of the NRA. Electrochemical nitrate reduction is regarded as a sustainable alternative approach for the synthesis of ammonia. It is important to design and develop advanced electrocatalysts to improve the nitrate reduction to ammonia (NRA) activity. Herein, an efficient boron-doped copper nanowire electrocatalyst, B-Cu NWs/CF, for the NRA was successfully synthetized. The incorporation of electron deficient boron atoms into copper nanowires resulted in the electron localization with the partially empty Cu 3 d orbitals and improved significantly the catalytic activity of Cu active sites. The FE, nitrate conversion rate, the ammonia selectivity, and yield rate for the NRA catalyzed by B-Cu NWs/CF achieved 94.41 ± 0.12 %, 100.02 ± 0.94 %, 96.58 ± 1.5 %, and 0.276 ± 0.00296 mmol·h−1·cm−2, respectively, remarkably superior to those of the pristine Cu NWs/CF and most of recently reported copper-based catalysts. And B-Cu NWs/CF exhibited the outstanding stability with high activity. The DFT calculations confirmed that the incorporation of boron into copper nanowires effectively inhibited the hydrogen evolution and the production of other reaction by-products. Importantly, the incorporation of boron significantly enhanced the adsorption of the *NO 3 intermediate on the copper surface and greatly reduced the activation barrier of *NO→*HNO. This work presents a new idea to devise highly active catalysts by the incorporation of nonmetal to adjust the activity of the NRA and inhibit the production of by-products. [ABSTRACT FROM AUTHOR]

[Display omitted] • The homogeneous Ru 0.5 Ir 0.5 alloy was fabricated by a facile reduction method. • Ru 0.5 Ir 0.5 ||Ru 0.5 Ir 0.5 shows outstanding electrocatalytic activity and stability. • The leaching of Ru produces protective skeleton to prevent its further dissolution. • The origin of excellent catalytic activity and stability of the alloy was proposed. Developing bifunctional electrocatalysts with high activity and long-term stability over the whole pH range is still a great challenge. Herein, the unsupported RuIr alloys are reported as robust electrocatalysts for pH-universal overall water splitting. The as-synthesized Ru 0.5 Ir 0.5 alloy exhibits unexpected low overpotentials of 4, 28, 16 mV for hydrogen evolution reaction (HER) and 160, 176, 248 mV for oxygen evolution reaction (OER) at 10 mA cm−2 in 0.5 M H 2 SO 4 , 1.0 M KOH and 1.0 M PBS solutions, respectively. Especially, the Ru 0.5 Ir 0.5 ||Ru 0.5 Ir 0.5 cell only needs voltages of 1.44, 1.48 and 1.51 V in the three environments to reach the same current density for overall water splitting and can continuously operate for more than 400, 100 and 100 h. Comprehensive studies verify that the excellent electrocatalytic performance of Ru 0.5 Ir 0.5 originates from the uniform arrangement of Ru and Ir atoms in the alloy, which leads to the leaching of an appropriate amount of Ru atoms and thus produces a protective skeleton composed of high valence Ir (IV) to prevent further dissolution of Ru. In addition, the weak coupling between Ru and Ir makes electron transfer from Ir to adjacent Ru as active sites, resulting in optimal adsorption strength for key intermediates. [ABSTRACT FROM AUTHOR]

Developing easy-to-make and excellent bifunctional electrocatalysts for water splitting over a wide pH range is a challenging yet appealing topic. Herein, based on integration of vacancy engineering and electronic modulation, a high-performance v s -Ru-Ni 9 S 8 electrocatalyst for water splitting was constructed via a cost-effective one-step hydrothermal method. Under the synergistic regulation of Ru-doping and sulfur vacancies, the v s -Ru-Ni 9 S 8 exhibited the outstanding electrocatalytic performance and long-time durability, along with ultra-low OER overpotentials of 218 and 268 mV at 100 and 300 mA cm−2 in alkaline electrolyte and low HER overpotentials of 56, 131, 94 mV at 10 mA cm−2 in acidic, neutral, alkaline electrolyte. Impressively, 1.47 and 1.68 V of voltages were needed to achieve 10 and 300 mA cm−2 for the v s -Ru-Ni 9 S 8 (+, -) cell. Our DFT results revealed that the doping Ru atom played a crucial role in regulating electron density in OER, rather than served as a catalytic active site. More importantly, we corroborated the active Ni-vacancy pair composed of Ni atom and sulfur vacancy, as an active site, and its catalytic synergy in OER. Especially, a vacancy-metal synergetic mechanism for OER was suggested to correctly describe the OER process and the role of vacancy in catalytic process. Our work provides a simple and effective strategy for fabricating high-performance catalysts and an in-depth understanding of OER. [Display omitted] ● A high-performance nickel-based sulfide electrocatalyst for overall water splitting was constructed. ● Improving synergistically the catalytic activity via electronic modulation and vacancy engineering was revealed. ● An active Ni-vacancy pair as an active site and its catalytic synergy in OER were corroborated. ● A vacancy-metal synergetic mechanism for OER was suggested. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electronic modulation strategy is adopted to improve electrocatalytic activity. • Designed Cr-CoP/CP emerges excellent pH-universal HER and alkaline OER performances. • Activation process of active sites of transition metal phosphides is revealed. Herein, we constructed 3D self-supported Cr-doped CoP nanoarrays (Cr-CoP/CP) to promote water electrolysis. Due to the electronic modulation effect, Cr-CoP/CP exhibits preeminent activity toward pH-universal hydrogen evolution reaction (HER), with low overpotentials of 47, 131 and 67 mV at 10 mA·cm−2 in acidic, neutral, and alkaline medium, respectively. Cr-CoP/CP also shows outstanding performance for oxygen evolution reaction (OER) with an overpotential of 251 mV at 10 mA·cm−2 in alkaline electrolyte. And the voltages of 1.59 and 1.73 V are required to achieve 10 and 100 mA·cm−2 for the Cr-CoP/CP(+,-) cell. Importantly, the X-ray photoelectron spectroscopy and theoretical calculations confirmed the activation process of active sites for transition metal phosphides. In the early stage of electrocatalysis, M−P bonds of transition metal phosphides undergo the transformation from covalent to ionic bonds, and finally form metal cations as active sites. This work is of great significance for understanding the process of electrochemical water splitting catalyzed by transition metal phosphides. [ABSTRACT FROM AUTHOR]

• The controlled synthesis of hierarchical hollow CoLDH nanocages is realized via etching the Metal−Organic Frameworks (MOFs). • The evolving process of MOFs into hollow CoLDH nanocages is investigated in detail for the first time. • The CoLDH presents an effective OER performance. Morphology engineering is an effective means to improve the performance of electrocatalysts. Herein, the controlled synthesis of hierarchical hollow cobalt layered-double-hydroxide (CoLDH) nanocages was realized via etching the metal − organic frameworks (MOFs) for oxygen evolution reaction (OER). The etching process of MOFs into hollow CoLDH nanocages was investigated in detail, and the results demonstrate that the structure and morphology of the electrocatalysts could be regulated by the concentration of Co2+ cation. The obtained hollow CoLDH nanocages have obvious mesoporous characteristics and high electrochemical active surface areas by precise regulation. Benefiting from their unique hollow nano-architecture, the CoLDH electrocatalysts exhibit excellent electrocatalytic activity for OER in alkaline electrolyte, achieving a low overpotential of 290 mV at a current density of 10 mA cm−2 and a good stability. The present work provides a feasible strategy for optimizing the structure and morphology of the electrocatalyst materials and in-depth understanding of their electrocatalytic activity. [ABSTRACT FROM AUTHOR]

• Selective phosphorization strategy is adopted to construct Ni 2 P/MoO 2 /NF HNRs. • Spontaneously electron transfer contributes to strong electronic coupling effect. • Ni 2 P/MoO 2 /NF can act as multifunctional electrocatalyst for HER, OER, and UOR. Rational design of heterogeneous electrocatalysts is an effective approach to synergistically promote hydrogen production for renewable energy conversion. Herein, a selective phosphorization strategy by controlling the only phosphorization of higher activity Ni atoms in precursor to construct Ni 2 P/MoO 2 /NF heterostructure nanorods arrays (Ni 2 P/MoO 2 /NF HNRs) electrocatalyst is realized. By effective interface construction, the strong electronic coupling effect is induced by spontaneously electron transfer across Ni 2 P/MoO 2 heterointerface, which modulates the electronic structure and enhances intrinsic catalytic activity, leading to outstanding electrocatalytic activities and long-time durability in alkaline electrolyte. The Ni 2 P/MoO 2 /NF HNRs present ultralow overpotential of 34 mV at 10 mA·cm−2 for hydrogen evolution reaction. Impressively, when coupled it for urea-assisted electrolyzer, the potential as low as 1.35 V is needed to achieve 10 mA·cm-2. Experimental and density functional theory results reveal that the strong electronic coupling effect enhances the synergy effect between Ni 2 P and MoO 2 , beneficial for boosting the H 2 production. [ABSTRACT FROM AUTHOR]