Engineering interfacial charge transfer channel for efficient photocatalytic H2 evolution: the interplay of CoPx and Ca2+ dopant

Abstract Cobalt phosphide (CoPx) has been developed as a cost-effective cocatalyst for photocatalytic H2 evolution with the advantages of excellent conductivity, strong reduction ability, and good thermal and chemical stability. In this work, a facile preparation strategy was proposed to fabricate ultrafine CoPx nanoparticles on the surface of CdS. The effective H2 production over ultrafine CoPx nanoparticles has been realized. In addition, we found Ca2+ as an alkaline earth metal ion can promote the interaction between CdS and CoPx. Both experimental results and density function theory indicate that the Ca2+ dopant can act as surface trapping sites on CdS and lead to efficient separation of photogenerated electron-hole pairs. The integration of CoPx and Ca2+ dopant can synergistically enhance both photogenerated electron-hole separation as well as interfacial charge transfer, which enables a remarkable improvement on the H2 generation performance of CdS. The photocatalytic H2 generation rate of Ca-modified CoPx@CdS can reach up to 2441.5 μmol h-1 under optimal conditions with the apparent quantum efficiency as high as 35.4% at 420 nm. This finding motivates the development of simplified fabrication procedures for constructing and modifying cobalt active sites with efficient photocatalytic H2 generation performance.