The synergy electron mediator and sulfur vacancies regulating charge transfer for piezo-photocatalytic H2O2 and H2 generation

Piezo-assisted photocatalysis has witnessed considerable success in addressing environmental pollutants and energy shortages, but challenges persist in achieving high-efficiency electron transfer in heterojunction. Herein, a ternary piezoelectric semiconductor heterojunction KNbO3/NiCo2S4/CdIn2S4-SV(KSCIS)was constructed employing a strategy of metal-like combined sulfur vacancies (SV) to boost their piezo-photocatalytic performance. The photocurrent density of the optimal sample KSCIS-9 is up to 2.2 μA/cm2, which is 2.8 times the binary heterojunction KNbO3/CdIn2S4-SV. Under both mechanical vibration and light irradiation, the production rates of H2O2 and H2 of KSCIS-9 are 47.33 mM h−1 g−1 and 9.59 mmol h−1 g−1, which are 2.8 and 2.0 times photocatalysis alone, and 10.6 and 5.3 times the piezoelectric catalysis alone. The density functional theory (DFT) calculations and UV–Vis diffuse reflection spectra (DRS) indicate that sulfur vacancies change bandgap and enhance the likelihood of photogenerated carrier generation. This work demonstrates that NiCo2S4 as the electron transfer medium, sulfur defects, and band bending induced by the piezoelectric polarization field, effectively promote the separation and transport of photogenerated carriers at the heterojunction interface and significantly improves the catalytic performance of heterojunction.