Constructing Z-scheme heterojunction with a special electron transfer path and more active sites over MnS/D-PCN for photocatalytic H2 evolution

Highlights: • Urea groups acted as the docking sites of MnS and hydrogen evolving centers. • The formation of ligating linkage provided a charge transfer pathway. • The photocatalytic H₂ evolution over MnS/D-Melon followed the Z-scheme mechanism. Given that low hydrogen active sites and serious photoexcited electron-hole recombination greatly limits the solar-to-chemical energy conversion efficiency, a synergistically integrated strategy of the defect engineering and the construction of Z-scheme heterojunction is introduced to the design of PCN photocatalyst, a strand-like polymer carbon nitride, in this work to resolve these problems and enhance the photocatalytic activity. The PHE activity was intimately related to MnS compositions. A maximum hydrogen evolution rate of 670.5 μmol/g/h could be achieved over 5% MnS/D-PCN composite, almost 5 times the rate of D-PCN and 18.4 times higher than that pristine PCN. This high PHE activity of MnS/D-PCN was attributed to the following factors: defects effects and Z-scheme heterojunction. We found that defects sites, on one hand, were the docking sites of MnS through a linkage to bridging the MnS and defected PCN, which offered an efficient spatial transfer path for electron-hole pairs at the interface, on the other hand, acted as the hydrogen evolving centers gathering the excited photoelectrons from D-PCN and MnS. Furthermore, Z-scheme pathway greatly enhanced the photoexcited charge separation due to their enormous driving force in internal electric field of p-n heterojunction.