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Exploration of cost-effective high-performance non-noble-metal-based electrocatalysts for the hydrogen evolution reaction (HER) has attracted huge attention. In this work, a nitrogen doping method is adopted to construct self-supported, N-doped NiO nanosheet arrays (N-NiO) as an effective HER electrocatalyst. The N-NiO nanosheet arrays are firmly anchored on a nickel foam substrate, forming a free-standing integrated electrode with an open nanostructure. By virtue of its larger electrochemical active surface areas and better electron conductivity, the N-NiO electrode has admirable electrocatalytic HER performance with a low overpotential (154 mV at a current density of 10 mA cm−2) and a low Tafel slope of 90 mV dec−1. In addition, the N-NiO nanosheet arrays exhibit relatively stable electrocatalytic activity after a 10 h continuous test in an alkaline solution. Our reported rational design principle and optimization strategy provide a powerful way to construct advanced transition-metal-based electrocatalysts for the HER. [ABSTRACT FROM AUTHOR]

The tailored construction of non-noble metal bifunctional electrocatalysts for high-efficiency oxygen/hydrogen evolution reactions (OER/HER) is vital for the development of electrochemical energy conversion. Herein, we report a powerful combined wet chemical method to fabricate a novel binder-free NiFe layered double hydroxide@Ni3S2 (NiFe LDH@Ni3S2) heterostructure as an efficient bifunctional electrocatalyst for overall water splitting. The hydrothermal-synthesized NiFe LDH nanosheets are uniformly coated on the Ni3S2 nanosheet skeleton forming 3D porous heterostructure arrays. By virtue of its synergistic advantages, including its binder-free characteristics, increased catalysis sites and structural stability, the as-obtained NiFe LDH@Ni3S2/NF electrode exhibits low overpotentials of 184 and 271 mV at 20 mA cm−2 for HER and OER in 1 M KOH, respectively. Notably, a low operation potential of 1.74 V at a current density of 20 mA cm−2 is achieved for overall water splitting with a stable cycling life. In addition, the intimate composite structure and sensitive interface of NiFe LDH@Ni3S2 are responsible for the good electrocatalytic activity with a low Tafel slope, fast reaction kinetics and high stability. The versatile fabrication protocol and heterostructure interface engineering provide a new way to construct other bifunctional and cost-effective electrocatalysts for electrocatalysis. [ABSTRACT FROM AUTHOR]

Graphical abstract The P-O-Fe bond and the redox cycle between N-P-O-Fe-O and N-P-O-Fe-O 2 on atomically dispersed Fe-N-P-C complex catalyst prepared directly form woody biomass efficiently reduced adsorption strength of OH*, which leads to outstanding ORR activity. Highlights • Atomically dispersed Fe-N-P-C catalysts produced from woody biomass. • Outstanding ORR performance achieved. • Fe charge in the active site identified as descriptor. • P-O-Fe bond and the redox cycle of active sites resulted in the high activity. Abstract Development of cost-effective electrocatalysts as an alternative to platinum for oxygen reduction reaction (ORR) is of great significance for boosting the applications of green energy devices such as fuel cells and metal-air batteries. Here we report a nitrogen and phosphorus tri-doped hierarchically porous carbon supported highly cost-effective, efficient and durable Fe single-site electrocatalyst derived from biomass. Combined aberration-corrected HAADF-STEM, XPS and XAFS measurements and theoretical calculations reveal the atomically dispersed Fe-N-P-C-O complex as the dominant active sites for ORR. This work also shows the design principle for enhancing the ORR activity of single Fe site catalysts with higher Fe charge, which can be manipulated by the coordinated structure in the active centre. Theoretical calculations reveal that the main effective sites are singleN-P-O-Fe-O centers, where the associated P-O-Fe bond can significantly lower the stability of strongly adsorbed O* and OH* on the catalytically active sites and thus give rise to enhanced ORR performance. The insights reported here open a new avenue for constructing highly efficient molecule-like heterogeneous catalysts in electrochemical energy technologies. [ABSTRACT FROM AUTHOR]

Rational construction and smart modification of cost‐effective and high‐performance electrocatalysts are of great importance for the development of high‐efficiency electrochemical hydrogen evolution reaction (HER). Molybdenum selenide (MoSe2)‐based nanocomposites are considered as one of the most promising electrocatalysts for HER, owing to its superior catalytic activity, long‐term stability, and relatively low cost. In this Review, we summarize the recent progress on MoSe2‐based electrocatalysts for HER including synthesis methods, electrochemical properties and catalytic mechanisms. The mechanism of HER and influencing factors of MoSe2‐based electrocatalysts are briefly reviewed. Additionally, the benefits and the difficulties of different synthetic methods are also summarized. Furthermore, diverse modification strategies to increase electrocatalytic activity of MoSe2 are thoroughly discussed. Finally, the challenges and outlook on the advancement of MoSe2‐based electrocatalysts are presented. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile and controllable preparation method was adopted. • The detailed mechanism of hydrogenation process was elucidated. • The prepared electrocatalyst exhibits outstanding catalytic activity. • DFT calculations further verify the underlying mechanisms of catalytic performance. Exploration of high-efficiency non-noble-metal-based electrocatalysts towards Hydrogen evolution reaction (HER) is critical for water electrolysis. In this work, we adopt a facile hydrothermal deposition plus hydrogen reduction strategy to fabricate self-supported Co@CoO core/shell nanowire arrays as a high-performance electrocatalyst for HER. The Co@CoO nanowire arrays are firmly anchored on the nickel foam substrate, forming an integrated electrode with excellent stability. The formation mechanism of the unique Co@CoO core/shell nanowire arrays is also explored. By virtue of the superior intrinsic catalytic activity of CoO shell and excellent electrical conductivity of Co core, the Co@CoO electrode exhibits significantly promoted catalytic activity for HER with an ultra-low overpotential (76 mV at 10 mA cm-2) in alkaline solution, which is superior to almost all the reported CoO-based electrocatalysts. Moreover, the Co@CoO electrode also yields superior long-term durability without any significant performance degradation. DFT calculations further verify the underlying mechanisms. Our proposed optimization strategy sheds light on the development of high activity earth-abundant-metal-based electrocatalyst for hydrogen evolution. [ABSTRACT FROM AUTHOR]

Nitrogen-doped vertical graphene as a metal-free catalyst for HER exhibits a good activity and an excellent stability, which can be ascribed to the optimization of ΔG (H) by N doping and the robust structure of VG. • Nitrogen doped vertical graphene metal-free electrocatalyst for HER is developed. • Enhanced electrocatalytic activity and excellent stability are achieved with N-VG. • DFT calculations reveal the two enhancement mechanisms of N-doping towards HER. Building up efficient water electrolysis system relays on the development of highly active, cost-effective, and stable electrocatalysts. Carbon-based metal-free catalysts are one of the promising candidates for this purpose. Herein, we report a facile strategy to synthesize nitrogen doped vertical graphene (N-VG) array for catalyzing hydrogen evolution reaction (HER) in acidic electrolyte. The resultant N-VG metal-free catalyst exhibits enhanced HER performance with an overpotential of 290 mV at 10 mA cm−2 and good cycling stability. The enhanced performance is due to the enlarged surface area and optimization of electronic structure induced by the introduction of N heteroatom. Moreover, two possible enhancement mechanisms of N-VG are revealed with first-principle calculations. Our work further demonstrates the effectiveness of N doping on enhancement of HER. [ABSTRACT FROM AUTHOR]

Development of low‐cost, efficient, and robust electrocatalysts to replace precious platinum catalysts for oxygen reduction reaction (ORR) is urgent to boost the applications of green energy devices such as fuel cells and metal–air batteries. Herein, a low‐cost, simple, and easy‐to‐scale method to develop sustainable and cost‐effective ORR carbocatalysts via impregnation followed by pyrolysis of different renewable woody biomass is reported. Aberration‐corrected high‐angle annular dark field scanning transmission electron microscopy, X‐ray photoelectron spectroscopy, and X‐ray absorption near edge structure measurements show that the nitrogen‐ and phosphorus‐promoted atomically dispersed iron is mainly responsible for the high ORR activity. Moreover, by a mimic of the natural pine materials derived Fe‐based electrocatalyst, introducing external Fe precursor into the biomass can generate targeted well dispersed Fe complex catalysts, which is not very much dependent on the biomass types. The insights revealed here can shed new light on the development of sustainable and cost‐effective ORR carbocatalysts from biomass. Nitrogen‐ and phosphorus‐decorated sustainable carbocatalysts with excellent oxygen reduction reaction activities that outperformed many state‐of‐the‐art electrocatalysts are produced only from woody biomass using a simple impregnation‐pyrolysis method. Precise characterizations reveal that the atomically dispersed Fe–N–P–C complex structure formed with trace Fe species initially existed in woody biomass is responsible for the high activity. [ABSTRACT FROM AUTHOR]