Highly photoactive Cu2O films with enhanced crystallinity for PEC water splitting

This study explores the deposition of single-phase Cu 2 O films using magnetron sputtering techniques for photoelectrochemical hydrogen production, with a focus on comparing Direct Current Magnetron Sputtering (DCMS) and High-Power Impulse Magnetron Sputtering (HiPIMS). The HiPIMS technique demonstrated several advantages over DCMS, including more straightforward deposition, improved crystallinity, and higher photocurrent density, j ph , during linear sweep voltammetry measurements. As a result, films prepared by HiPIMS became the focus of further optimization. The effects of key deposition parameters – such as substrate temperature, oxygen partial pressure, film thickness, and post-deposition annealing – on the structural and photoelectrochemical properties of Cu 2 O films were systematically investigated. The optimized films exhibited a fully densified microstructure, high crystallinity, and enhanced j ph values. The highest j ph of − 3 mA/cm 2 at 0.03 V vs. RHE was achieved for a 5-μm thick film deposited at an oxygen partial pressure of 0.42 Pa and a substrate temperature of 500 °C, followed by post-annealing at 600 °C in a vacuum. This represents the highest j ph value reported to date for a bare Cu 2 O photocathodes. These results highlight the potential of HiPIMS-deposited Cu 2 O films for efficient photoelectrochemical (PEC) water splitting.