A 4e-–2e- cascaded pathway for highly efficient production of H2 and H2O2 from water photo-splitting at normal pressure

Abstract

Overall water solar-splitting is one of the most attractive candidates to break water down into hydrogen peroxide (H2O2) and hydrogen (H2) in a cheapest and cleanest way (i.e., 2H2O →H2O2+ H2). However, the generated intermediate H2O2 in the 2e− process would poison the catalysts. Hence, it is an ideal pathway to generate H2O2 by 4e−–2e− cascaded process (H2O→O2→H2O2), which is more thermodynamically advantageous and can also avoid the catalyst poisoning by the intermediate product of H2O2. Herein, we report CoP modified by carbon dots (CoP/CDs composite) to realize simultaneous generation of H2 and H2O2 via a 4e−–2e− cascaded pathway, coupling photocatalytic water oxidation (4e−) and oxygen reduction reaction (2e−). The optimal CoP/CDs sample displays a prominent H2 yield of 239 μmol/h/g and H2O2 production rate of 466 μmol/h/g without sacrificial agent at normal pressure. It exhibits the highest photocatalytic activity for water decomposition to produce H2 and H2O2 simultaneously. Moreover, the quantum efficiency of the as-prepared sample is 2.05 % at 535 nm. This work offers a novel approach to achieve high-efficiency production of H2 and H2O2 by photocatalytic water splitting.