A novel p-type CoSe2 co-catalyst cooperated with hematite for boosting photoelectrochemical water splitting

Abstract

Fe2O3-based photoelectrodes hold promise for photoelectrochemical water splitting due to their cost-effectiveness and stable chemical properties. However, Fe2O3-based photoelectrodes face limitations including low bulk conductivity and severe surface recombination of photo-generated charge carriers, which adversely affect their performance. To address these challenges, a novel p-type CoSe2 surface co-catalyst was developed to establish a Ti-Fe2O3/CoSe2 p-n heterojunction. By incorporating a Ti4+ doping strategy, the resulting Ti-Fe2O3/CoSe2 p-n heterojunction demonstrated a significant increase in photocurrent density, reaching 2.85 mA/cm2 at 1.23 VRHE under 100 mW/cm2 illumination. The corresponding IPCE achieved 60.14 % under 365 nm light irradiation, nearly 5 times higher than that observed on pristine Fe2O3. Besides Ti4+ dopant, the improvement can be attributed to the p-type CoSe2 surface co-catalyst, which created a built-in electric field at the interface between CoSe2 and Ti-Fe2O3, effectively suppressing electron tunneling from the photoelectrode to the electrolyte and reducing surface carrier recombination. This study improves our understanding of the water splitting catalytic reaction on CoSe2-derived heterojunctions and provides insights for the rational design of photoelectrodes used in photoelectrochemical water splitting.