Highly efficient sputtered Ni-doped Cu2O photoelectrodes for solar hydrogen generation from water-splitting

Abstract

Hydrogen gas can be converted to electricity through fuel cells and is considered as a friendly energy source. Herein, pure Cu2O and Ni-doped Cu2O thin films were deposited on glass substrates using the RF/DC-sputtering technique for hydrogen production via the photoelectrochemical (PEC) water-splitting process. The preferred orientation for pure and Ni-doped Cu2O films was (111) crystallographic plane. The average nanograins size was decreased from 32.17 nm for pure to 10.40 nm through the doping process with Ni content. Field-emission scanning electron microscopy (FE-SEM) and ImageJ analysis showed that the pure Cu2O and Ni-doped Cu2O were composed of normal distribution of nanograins in a regular form. The optical bandgap of the Cu2O film was decreased from 2.35 eV to 1.9 eV after doping with 2.6 wt% of Ni-dopants. The photoluminescence (PL) spectra for all the sputtered films were recorded at room temperature to examine the effect of Ni-dopants in the Cu2O lattice. Pure and Ni-doped Cu2O films were applied for PEC water splitting for hydrogen (H2) production under white light and monochromatic illumination. The PEC studies displayed that increasing the Ni content up to 2.6 wt% in the pure Cu2O films led to an increase in the photocurrent density to reach −5.72 mA/cm2. The optimum photoelectrode was studied for reproducibility, stability, and electrochemical impedance. The incident photon to current conversion efficiency (IPCE%) was 16.35% at 490 nm, and the applied bias photon to current conversion efficiency (ABPE%) was 0.90% at 0.65 V. Consequently, Ni-doped Cu2O photoelectrodes are efficient and low-cost for practical and industrial solar H2 production.