p-n heterojunction constructed by y-Fe2O3 covering CuO with CuFe2O4 interface for visible-light-driven photoelectrochemical water oxidation

Fe2O3 is a promising n-type semiconductor as the photoanode of photoelectrochemical water-splitting method due to its abundance, low cost, environment-friendly, and high chemical stability. However, the recombination of photogenerated holes and electrons leads to low solar-to-hydrogen efficiency. this work, to overcome the recombination issue, a p-type semiconductor, CuO, is introduced underneath the y-Fe2O3 to synthesize y-Fe2O3/CuO on the FTO substrate. Along with the formation of p-n heterojunc-tion, CuFe2O4 is in situ generated at the interface of y-Fe2O3 and CuO. The existence of Cu2O in CuO CuFe2O4 promotes the charge transfer from CuO to y-Fe2O3 and within CuFe2O4, respectively, resulting creating an internal electric field in y-Fe2O3/CuO and leading to the conduction band of CuO bending and y-Fe2O3 bending down. Additionally, Cu(II) in CuFe2O4 contributes to fast electron capture. Consequently, the charge transfer efficiency and charge separation efficiency of photo-generated holes are promoted. Hence, y-Fe2O3/CuO exhibits an enhanced photocurrent density of 13.40 mA cm-2 (1.9 times higher than y-Fe2O3). The photo corrosion resistance of CuO is dramatically increased with the tection of CuFe2O4, resulting in superior high chemical stability, i.e. 85% of the initial activity remains after a long-term test. CO 2023 Elsevier Inc. All rights reserved.