Nitrogen-rich carbon nitride (CN) coupled with oxygen vacancy TiO arrays for efficient photocatalytic HO production.

Developing efficient and facilitated recycling photocatalysts for HO formation is an ideal strategy for solar-to-chemical energy conversion. In this work, we synthesized ultrathin CN nanosheets through the process of thermal polymerization and polyvinylpyrrolidone (PVP)-assisted solvent exfoliation. Subsequently, the obtained ultrathin CN nanosheets were tightly attached to the surface of TiO arrays, resulting in an enhanced photocatalytic HO production rate. The density functional theory (DFT) calculations demonstrate that an internal electric field (IEF) is generated between the TiO array and the ultrathin CN due to the different work functions. The presence of IEF provides an additional driving force for carrier separation and transfer in the heterointerface. Benefitting from this unique strategy, the optimal heterojunction obtains the highest HO formation rate (2.93 μmol/L/min), which is about 4.1 times than that of TiO arrays. The rotating disk electrode (RDE) analysis manifests HO formation through 2e-dominated oxygen reduction reaction (ORR). This research provides an innovative strategy for assembling a type-II heterojunction with a useful IEF for efficient photocatalytic HO production.