The development of cobalt phosphide co-catalysts on BiVO4 photoanodes to improve H2O2 production

Photoanodic hydrogen peroxide (H 2 O 2 ) production via water oxidation is limited by low yields and poor selectivity. Herein, four variations of cobalt phosphides, including pristine CoP and Co 2 P crystals, and two mixed-phase cobalt phosphides (CoP/Co 2 P) with different ratios, were applied as co-catalysts on the BiVO 4 (BVO) photoanode to improve H 2 O 2 production. The optimal yield and selectivity were approximately 9.6 µmol‧h −1 ‧cm −2 and 25.2 % at a voltage bias of 1.7 V vs reversible hydrogen electrode (V RHE ) under sunlight illumination, respectively. This performance is approximately 1.8 times that of pristine BVO photoanode. The roles of the Co and P sites were investigated. In particular, the Co site promotes the breaking of one H O bond in water to form OH • radicals, which is the rate-determining step in H 2 O 2 production. The P site plays an important role in the desorption of H 2 O 2 formed from the catalyst, which is responsible for the recovery of fresh catalytic sites. Among the four samples, Co 2 P exhibited the best performance for H 2 O 2 production because it had the highest rate of OH • formation owing to its improved accumulation property. This study offers a rational design strategy for co-catalysts for photoanodic H 2 O 2 production.