Sulfur-vacancy-modified ZnIn2S4/TpPa-1 S-scheme heterojunction with enhanced internal electric field for boosted photocatalytic hydrogen production

The construction of S-scheme heterojunction is an effective approach to accelerate photocarrier transfer and improve charge utilization, thus promoting photocatalytic hydrogen evolution. Herein, we report, for the first time, the construction of a S-scheme heterojunction based on sulfur-vacancy-modified ZnIn2S4 (Sv-ZIS) and covalent organic frameworks (COFs), by in-situ growth of Sv-ZIS on COF TpPa-1 (composed of 1,3,5-triformylphloroglucinol and p-phenylenediamine). Under visible-light irradiation, in the absence of cocatalyst, the optimal Sv-ZIS/TpPa-1 (5:1) (with a Sv-ZIS: TpPa-1 mass ratio of 5:1) achieved an enhanced hydrogen production rate of 2745 μmol g−1 h−1 than parent ZIS/TpPa-1 (5:1), with an AQE of 4.67% at 420 nm. Theoretical calculations confirmed that sulfur-vacancy enlarged the internal electric field (IEF) in Sv-ZIS/TpPa-1, leading to greater interfacial charge transfer from Sv-ZIS to TpPa-1 than that of ZIS to TpPa-1. The enhanced IEF and rapid separation and transfer of photocarriers following S-scheme charge transfer mechanism synergistically guaranteed the improved performance.