Joule heating synthesis of well lattice-matched Co2Mo3O8/MoO2 heterointerfaces with greatly improved hydrogen evolution reaction in alkaline seawater electrolysis with 12.4 % STH efficiency

Herein, through a rapid Joule heating method, we have successfully prepared well lattice-matched Co2Mo3O8/MoO2 heterointerfaces on Ni foam (Co2Mo3O8/MoO2/NF) in only 130 s. Notably, the rapid Joule heating can effectively avoid oxidation of catalyst caused by prolonged heating and achieve rich uncoordinated Mo4+ sites, which contributed to the enhanced electrocatalytic performance in hydrogen evolution reaction (HER). As-prepared Co2Mo3O8/MoO2 delivered remarkable HER activity (23 mV at 10 mA cm−2), which was comparable to Pt-based electrocatalyst. As-prepared sample also revealed excellent stability at 200-h test in electrocatalytic splitting of alkaline seawater. Of particular note, the solar-driven H2O-H2 electrolyzer also showed a promising solar-to-hydrogen (STH) efficiency of 12.4 %. The cell voltage for the home-made anion exchange membrane (AEM) seawater electrolyzer was only 2.13 V at 200 mA·cm−2 at 50 °C, and only 4.7 kW-h required to produce 1 m3 of H2. DFT calculations revealed that the electron redistribution spontaneously takes place at Co–O–Mo bonds at Co2Mo3O8/MoO2 heterointerfaces, which could regulate the electronic structure and d-band center of Mo sites, and then achieve high-efficiency adsorption of H2O on Mo sites and near-zero hydrogen-adsorption free energy on O sites. This study provided a new strategy to regulate the chemical states via Joule heating for highly efficient seawater splitting to evolve H2.