Impressive efficiency of zinc oxide-manganese oxide/MAX composite in two-electrode system for photovoltaic-electrolyzer water splitting

Abstract

The improvement and use of affordable and efficient electrocatalysts for complete water splitting are crucial for the future of energy supply. Here, a hybrid zinc oxide (ZnO)–manganese oxide (Mn3O4)/Ti3AlC2 (MAX) composite produced by a facile hydrothermal synthesis is utilized as a dual-function electrocatalyst for the hydrogen and oxygen evolution reactions (HER and OER, respectively). Its well-organized surfaces and bulky porous framework provide numerous catalytically active sites during electrochemical reactions, leading to significant improvement in the HER and OER activities. In particular, the ZnO and Mn3O4 phases increase the catalytic activity of the electrode, while the MAX phase enhances the conductivity and promotes low overpotential Ni sites through charge transfer effects. Consequently, the optimized ZnO-Mn3O4/MAX/Ni foam electrode exhibits relatively low overpotentials (η) of 244 and 340 mV at 20 mA cm−2 for the HER and OER at 1.0 M KOH, respectively. The electrodes also demonstrate exceptional long-term stability during cycling for both the HER and OER. A fully homemade water splitter, using these electrodes as anode and cathode, achieves a current density of 10 mA cm−2 at a cell voltage of only 1.62 V. When integrated with commercially available silicon-based solar cells, combined PV-EC water splitting devices enable increased hydrogen generation from stimulated sunlight. This study presents a typical demonstrated and proven strategy for real large-scale solar hydrogen generation using cost-effective PV-EC technology.