Quantitative Evaluation of Carrier Dynamics in Full-Spectrum Responsive Metallic ZnIn2S4 with Indium Vacancies for Boosting Photocatalytic CO2 Reduction

The influence of defects on quantitative carrier dynamics is still unclear. Therefore, full-spectrum responsive metallic ZnIn₂S₄ (V_In-rich-ZIS) rich in indium vacancies and exhibiting high CO₂ photoreduction efficiency was synthesized for the first time. The influence of the defects on the carrier dynamic parameters was studied quantitatively; the results showed that the minority carrier diffusion length (L_D) is closely related to the catalytic performance. In situ infrared spectroscopy and theoretical calculations revealed that the presence of indium vacancies lowers the energy barrier for CO₂ to CO conversion via the COOH* intermediate. Hence, the high rate of CO evolution reaches 298.0 μmol g^-1 h^-1, a nearly 28-fold enhancement over that with ZnIn₂S₄ (V_In-poor-ZIS), which is not rich in indium vacancies. This work fills the gaps between the catalytic performance of defective photocatalysts and their carrier dynamics and may offer valuable insight for understanding the mechanism of photocatalysis and designing more efficient defective photocatalysts.