Gd-doped CuBi2O4/CuO heterojunction film photocathodes for photoelectrochemical H2O2 production through oxygen reduction

Photoelectrochemical oxygen reduction reaction (ORR) toward H2O2 is highly desirable because only sunlight, O2 and water are required in the process. However, the corresponding studies are still at its infancy because of the lack of suitable photocathodes, especially inorganic semiconductor photocathodes. In this work, we report CuBi2O4/CuO (CBO/CuO) heterojunction submicrocrystalline film photocathodes with efficient ORR activity for H2O2 production. The heterojunction film photocathodes were prepared through thermal evaporation of Cu and Bi metals under vacuum and subsequent annealing treatment. Furthermore, the doping of Gd3+ ions into CBO/CuO could significantly enhance the yield of H2O2. As a result, the concentration of H2O2 could reach 1.3 mM within 30 min, which is 6 times higher than that obtained on the pristine CBO/CuO photocathode. The theoretical calculations suggested that the introduction of Gd could adjust the electronic structure of CBO surface and promote 2e ORR pathway for selective production of H2O2. Our work not only provides a new strategy for designing highly efficient photocathode for H2O2 production but also will evoke more interest in photoelectrocatalytic ORR through inorganic semiconductor photocathode.