Tuning nanosheet Fe2O3 photoanodes with C3N4 and p-type CoOx decoration for efficient and stable water splitting†
Abstract
Fe2O3 photoanodes are ideal candidates for photoelectrochemical (PEC) water splitting. However, the charge recombination in the bulk and at the photoanode/electrolyte interface decreases their PEC performance. Here, C3N4 and p-type CoOx are firstly decorated on Fe2O3 nanosheets for PEC performance enhancement and mechanism study. The photocurrent densities of Fe2O3/C3N4 and Fe2O3/C3N4/CoOx photoanodes are about 1.6 and 2 times at 1.23 V vs. RHE (reversible hydrogen electrode) compared with that of the Fe2O3 film (0.74 mA cm−2) under simulated sun light irradiation. Correspondingly, their photocurrent onset potentials are negatively shifted by about 0.09 and 0.19 V compared with that of Fe2O3 (0.81 VRHE). The solar-to-hydrogen conversion efficiency reaches 0.17% and the incident photo-to-current conversion efficiency (IPCE) achieves 81.7% at 385 nm for the Fe2O3/C3N4/CoOx hybrid photoanode. The matched band alignments between Fe2O3 and C3N4 result in more efficient charge separation, and the p-type CoOx cocatalyst reduces surface recombination and shows quicker water oxidation reaction kinetics at the semiconductor/electrolyte interface.