Phosphorylation of NiAl-layered double hydroxide nanosheets as a novel cocatalyst for photocatalytic hydrogen evolution

Abstract

In previous studies, it has been shown that phosphorus and phosphate can improve the conductivity, change the electronic structure, and accept electrons from catalysts. In this study, we obtained phosphorylated NiAl-layered double hydroxide (P-LDH) nanosheets and used them as a novel cocatalyst in photocatalytic hydrogen evolution. After assembly with g-C3N4 via an in situ process, these noble-metal-free composite photocatalysts showed superior photocatalytic hydrogen evolution activity. It was also found that the efficiency of H2 production on the optimal composite was 1.5 times that of Pt-modified g-C3N4. Characterization of the photocatalysts revealed that the effects of P-LDH were different from those of other bimetallic LDHs, showing a lower overpotential and faster reaction kinetics of H2 evolution. Moreover, it was found that P-LDH has a higher surface work function than that of g-C3N4, leading to the formation of an interfacial electric field from CN toward P-LDH. Therefore, modifying P-LDH can efficiently improve the interfacial charge transfer rate, suppress photogenerated charge recombination, and lower the surface overpotential of g-C3N4. This study serves as guidance on the design of more effective cocatalysts for photocatalytic hydrogen evolution reactions.