Efficient degradation of Congo Red by CuO-In2O3 p-n type heterojunctions photocatalyst enriched with oxygen vacancies

Utilizing the built-in electric field to drive carrier separation is a core process in photocatalysis. In this study, the preparation temperature of In2O3 was first optimized, and the photocatalytic performance of the In2O3 sample was found to be optimal at a calcination temperature of 350 degrees C. Building on this, p-n heterojunction with a strong built-in electric field was constructed by combining n-type semiconductor (In2O3) and p-type semiconductor (CuO) with a large Fermi level offset, facilitating directional transfer of photogenerated charges. Additionally, oxygen vacancies were introduced as carrier trapping sites to promote carrier separation. The Schottky curve displayed an inverted V shape, indicating the formation of p-n heterojunctions between CuO and In2O3. The photocatalytic performance was optimal when the molar ratio of CuO to In2O3 was 1:5, achieving an 83.0 % degradation degree of Congo Red aqueous solution after 60 min of illumination, with a first-order reaction rate constant (k) of 0.020 min- 1, which is 3.3 times that of In2O3-350.