Cu2O is a promising material for the hydrogen evolution reaction due to the favourable band gap. However

achieving a pure Cu2O phase typically requires high deposition temperatures. To overcome this

electrolyte pH modification was employed to synthesize pure Cu2O at room temperature. A key challenge in room-temperature electrodeposition is the slow deposition rate

which can be improved through photoelectrodeposition. This study explores the synthesis of pure Cu2O via controlled pH photoelectrodeposition for applications of the hydrogen evolution reaction. The results demonstrate that Cu2O films were successfully deposited in an alkaline electrolyte

with the best hydrogen evolution reaction catalytic performance observed at pH 8. This sample exhibited a low onset potential of 64 mV with respect to the standard reversible hydrogen electrode and a Tafel slope of 46 mV/dec. These findings provide the optimization of Cu2O synthesis for hydrogen production.