Work Function Difference-Driven Type-I Heterojunction: Efficient Interfacial Charge Transfer for Photocatalytic Hydrogen Evolution

Abstract

Abstract Photocatalytic hydrogen evolution represents a significant approach for converting solar energy into chemical energy. Nevertheless, conventional type-I heterojunctions face a bottleneck in charge recombination. In this study, a type-I heterojunction composed of CdS and COF, which exhibits a charge transfer mechanism similar to that of the ohmic junction, was fabricated via mechanical grinding. Distinct from the conventional type-I heterojunction, this system leverages the work function difference between CdS and COF to induce the formation of internal electric fields (IEFs). IEFs can facilitate the rapid migration of photogenerated electrons. TRPL results confirmed the effective extension of carrier lifetime in the CdS/COF heterojunction. The prolonged average carrier lifetime confirms the activation of ultrafast interfacial charge transfer channels, which indicates enhanced charge separation efficiency. Consequently, it surmounts the bottleneck of charge recombination in traditional type-I heterojunctions. In-situ XPS offers robust support for the migration path of photogenerated charges. The optimal catalyst CCS7 generated 301.84 μmol of hydrogen within 5 h, which was 3.3 times that of pure CdS. This Ohmic-like type-I heterojunction strategy offers a innovative paradigm for efficient photocatalytic hydrogen production.