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Rational design of efficient electrocatalysts is highly imperative but still a challenge for overall water splitting. Herein, we construct self-supported Co 3 N nanowire arrays with different Mo doping contents by hydrothermal and nitridation processes that serve as robust electrocatalysts for overall water splitting. The optimal Co 3 NÀ Mo 0.2 /Ni foam (NF) electrode delivers a low overpotential of 97 mV at a current density of 50 mA cm À 2 as well as a highly stable hydrogen evolution reaction (HER). Density functional theory (DFT) calculations prove that Mo doping can effectively modulate the electronic structure and surface adsorption energies of H 2 O and hydrogen intermediates on Co 3 N, leading to improved reaction kinetics with high catalytic activity. Further modification with FeOOH species on the surface of Co 3 NÀ Mo 0.2 /NF improves the oxygen evolution reaction (OER) performance benefiting from the synergistic effect of dual CoÀ Fe catalytic centers. As a result, the Co 3 NÀ Mo 0.2 @FeOOH/NF catalysts display outstanding OER catalytic performance with a low overpotential of 250 mV at 50 1 mA cm À 2 .The constructed Co 3 NÀ Mo 0.2 /NF j j Co 3 NÀ Mo 0.2 @FeOOH/NF water electrolyzer exhibits a small voltage of 1.48 V to achieve a high current density of 50 mA cm À 2 at 80 °C, which is superior to most of the reported electrocatalysts. This work provides a new approach to developing robust electrode materials for electrocatalytic water splitting.

Coupling the electrochemical oxidative upgrading of formaldehyde (FOR) with hydrogen evolution reaction (HER) toward energy-efficient H2 production and simultaneous chemical production is important, but it still faces huge challenges. Herein, a unique hierarchical heterojunction is designed by coupling a Ni­(OH)2 nanosheet with S-modified Ni species on a nickel foam substrate (S–Ni@Ni­(OH)2/NF) via a two-step strategy. The Ni­(OH)2 nanosheets with a large surface area contribute to offering sufficient sites for the grafting of S–Ni species, constructing a coupled heterostructure to realize greatly improved reaction kinetics for both HER and FOR processes. As a result, S–Ni@Ni­(OH)2/NF delivers an overpotential of 50 mV for HER at 10 mA cm–2 and a low potential of 1.36 V to acquire a current density of 50 mA cm–2 for FOR. For the HER||FOR-coupled system, the built-in electrolyzer only needs 1.58 V to realize 50 mA cm–2 as well as superior stability. This work presents a facile strategy to exploit bifunctional electrodes for hydrogen generation via an energy-saving way with coupled formaldehyde reforming.

The development of highly active non-precious metal electrocatalysts is crucial for advancing the practical application of hydrogen evolution reaction (HER). Doping engineering is one of the important strategies to optimize the electrocatalytic activity of electrocatalysts. Herein, we put forward a simple strategy to optimize the catalytic activity of MoO3 material by incorporating the Cu atoms into the interlayer (denoted as Cu-MoO3). The prepared Cu-MoO3 nanosheet has a larger surface area, higher conductivity, and strong electron interactions, which contributes to optimal reaction kinetics of the HER process. As a result, the Cu-MoO3 nanosheet only needs a small overpotential of 106 mV to reach the geometric current density of 10 mA cm−2. In addition, it also delivers a low Tafel slope of 83 mV dec−1, as well as high stability and Faraday efficiency. Notably, when using the Cu-MoO3 as a cathode to construct the water electrolyzer, it only needs 1.55 V to reach the 10 mA cm−2, indicating its promising application in hydrogen generation. This work provides a novel type of design strategy for a highly active electrocatalyst for an energy conversion system.