ABSTRACT:

Photo-assisted Mg/seawater batteries (PAMSBs) are attractive power source for marine equipment due to the advantage of simultaneous generation of electricity and hydrogen from seawater. Nonetheless, the serious photo-corrosion of photocathodes results in dissatisfactory battery performance, which substantially hinder their practical applications. Herein, we design a CuO/Cu₂O heterostructure as the photocathode of PAMSBs via a facile in-situ electrochemical strategy, successfully improve the photostability of Cu₂O. For half-cell photoelectrochemical (PEC) water splitting, the developed CuO/Cu₂O photocathode reveals a photocurrent density of ~2.2 mA cm^-2 at 0 V vs. RHE and enables nearly 100% retention of the initial photocurrent density after 2h long-term operation, more than 10 times stable than the bare Cu₂O photocathode. A PAMSB with a CuO/Cu₂O photocathode achieves a maximum power density of 22.67 mW cm^-2 and a hydrogen production rate of 1.18 mL cm^-2 min^-1, which are much higher than those obtained with a bare Cu₂O photocathode. This work provides a simple and convenient electrochemical strategy for in-situ fabrication of CuO/Cu₂O heterojunction photocathodes, and also demonstrate the feasibility of PAMSBs as a power source and a hydrogen generator, which lays foundation for its future marine application.

Keywords: CuO/Cu₂O photocathode; Mg/seawater battery; in-situ electrochemical strategy; seawater splitting; hydrogen evolution