Tuning nanosheet Fe2O3 photoanodes with C3N4 and p-type CoOx decoration for efficient and stable water splitting

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.