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[Display omitted] Exploiting highly efficient, cost-effective and stable electrocatalysts is key to decreasing hydrogen evolution reaction (HER) kinetics energy barrier. Herein, the alkaline HER kinetics energy barrier can greatly reduce by the joint strategies of the cation vacancy and heterostructure engineering, which is seldom explored and remains ambiguous. In this study, an efficient and stable copper foam-supported Cu 3 P-CoP heterostructure electrocatalyst with cation vacancy defects (defined as Cu 3 P-CoP-V Al /CF) was designed for HER via the successive coprecipitation, electrodeposition, alkali etching and phosphorization treatments. As anticipated, the as-obtained Cu 3 P-CoP-V Al /CF electrocatalyst reveals a remarkable catalytic activity for HER with a low overpotential of 205 mV at a current density of 100 mA·cm−2, a high turnover frequency value of 1.05 s−1 at an overpotential of 200 mV and a small apparent activation energy (E a) of 9 kJ·mol−1, while shows superior long-term stability at large current densities of 100 and 240 mA·cm−2. Systematic experiment and characterization data demonstrate that the formed cation vacancy could optimize the E a , leading to the decrease of the kinetic barriers of Cu 3 P-CoP/CF heterostructure, as well as the established heterogeneous interface induced a synergistic effect between biphasic components on boosting the kinetics toward HER. The results of density functional theory disclose that the synergistic effect of Cu 3 P-CoP heterostructure could decrease the energy barrier and optimize Gibbs free energy of hydrogen adsorption, resulting in the enhancement of intrinsic catalytic activity of Cu 3 P-CoP-V Al /CF. More significantly, the alkali-cell assembled by Cu 3 P-CoP-V Al /CF (cathode) and RuO 2 /CF (anode) behaves outstanding water splitting performance, delivering a current density of 10 mA·cm−2 at a relatively small applied voltage of 1.58 V, along with encouraging long-term durability. In addition, the alkaline Zn-H 2 O battery with Cu 3 P-CoP-V Al /CF as the cathode has been fabricated for the simultaneous generation of electricity and hydrogen, which displays a large power density of up to 4.1 mW·cm−2. The work demonstrates that rational strategy for the design of competent electrocatalysts can effectively accelerate the kinetics of HER, which supplies valuable insights for practical applications in overall water splitting. [ABSTRACT FROM AUTHOR]

Recently, perovskite (ABO3) nanomaterials have been widely explored as a class of versatile electrocatalysts for oxygen evolution reactions (OER) due to their remarkable compositional flexibility and structural tunability, but their poor electrical conductivity hinders hydrogen evolution reaction (HER) activity and further limits the large-scale application of perovskite oxide in overall water splitting (OWS). In this study, hollow-nanotube-structure LaxCo0.4Fe0.6O3−δ (x = 1.0, 0.9, and 0.8) perovskites with superior HER/OER activity were synthesized on nickel-iron alloy foam (denoted LaxCoFe/NFF) using hydrothermal with a subsequent calcination strategy. Among them, La0.9CoFe/NFF not only exhibited extraordinary HER electrocatalytic performance (160.5 mV@10 mA cm−2 and 241.0 mV@100 mA cm−2) and stability (20 h@10 mA cm−2), but also displayed significant OER electrocatalytic activity (234.7 mV@10 mA cm−2 and 296.1 mV@100 mA cm−2) and durability (20 h@10 mA cm−2), outperforming many recently reported HER/OER perovskite catalysts. The increase in oxygen vacancies caused by the introduction of La deficiency leads to the expansion of the lattice, which greatly accelerates the HER/OER process of La0.9CoFe/NFF. Additionally, the naturally porous skeleton can prevent catalysts from aggregating as well as delay the corrosion and dissolution of catalysts in the electrolyte under high applied potentials. Furthermore, the assembled two-electrode configuration, utilizing La0.9CoFe/NFF (cathode and anode) electrodes, only requires a low cell voltage of 1.573 V at 10 mA cm−2 for robust alkaline OWS, accompanied by remarkable durability over 20 h. This work provides inspiration for the design and preparation of high-performance and stable bifunctional perovskite electrocatalysts for OWS. [ABSTRACT FROM AUTHOR]

The search for low-cost, high-performance, and robust stability bifunctional electrocatalysts to substitute noble metals-based counterparts for overall water splitting to generate clean and sustainable hydrogen energy is of great significance and challenges. Herein, a high-efficient bi-functional nickel–iron phosphide on NiFe alloy foam (denoted as e-NFP/NFF) with 3D coral-like nanostructure was controllably constructed by means of alkali etching and the introduction of non-metallic atoms P. The unique superhydrophilic coral-like structure can not only effectively facilitate the exposure of catalytic active sites and increase the electroactive surface area, but also accelerate charge transport and bubble release. Furthermore, owing to the synergistic effect between the bicomponent of nickel–iron phosphides as well as the strong electronic interactions of the multiple metal sites, the as-fabricated catalyst behaves with excellent bifunctional performance for the hydrogen evolution reaction (overpotentials of 132 and 286 mV at 10 and 300 mA·cm−2, respectively) and oxygen evolution reaction (overpotentials of 181 and 303 mV at 10 and 300 mA·cm−2, respectively) in alkaline electrolytes. Impressively, cells with integrated e-NFP/NFF electrodes as a cathode and anode require only a low cell voltage (1.58 V) to drive a current density of 10 mA·cm−2 for overall water splitting, along with remarkable stability in long-term electrochemical durability tests. This study provides a tunable synthetic strategy for the development of efficient and durable non-noble metal bifunctional catalysts based on the construction of an elaborate structure framework and rational design of the electronic structure. [ABSTRACT FROM AUTHOR]

With the popularization of the concept of green development, hydrogen energy as an ideal energy carrier has been paid more and more attention. Electrochemical water splitting as one of the most effective means of hydrogen production has aroused wide interest. The development of high-activity and low-cost bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) plays a key role in hydrogen production via water splitting. Herein, hierarchical tube brush-like Co3S4@NiCo-LDH nanoarrays in situ grown on Ni foam were successfully synthesized via a three-step hydrothermal strategy. The as-fabricated catalyst exhibits simultaneously outstanding electrocatalytic performances for both the HER (overpotentials of 210 and 251 mV at 50 and 100 mA cm−2, respectively) and the OER (overpotentials of 262 and 320 mV at 100 and 300 mA cm−2, respectively) in 1 M KOH electrolyte. Impressively, the Co3S4@NiCo-LDH electrode presents a remarkable stability up to 100 h for the OER and HER at a high current density of 100 mA cm−2. Furthermore, by employing the Co3S4@NiCo-LDH as both the cathode and anode for overall water splitting (OWS), a low cell voltage of 1.59 V is required to deliver the current density of 10 mA cm−2, along with a remarkable durability. The superior electrocatalytic activity may be attributed to the following: (1) the in situ growth on the Ni foam substrate can not only improve structural stability and conductivity but also endow faster charge transfer as well as bubble release; (2) its peculiar structure provides large active surface areas, more accessible surface active sites and fast charge/mass transport; (3) the prominent synergistic effect between Co3S4 and NiCo-LDH justifies the excellent electrocatalytic activity for the HER and OER. This work will provide a novel idea for constructing effective bifunctional catalysts for hydrogen production via OWS. [ABSTRACT FROM AUTHOR]