Boosting the catalytic activity of a step-scheme In2O3/ZnIn2S4 hybrid system for the photofixation of nitrogen

Abstract

In this study, a step-scheme photocatalytic system comprising one-dimensional In2O3 nanorods and two-dimensional ZnIn2S4 nanosheets was developed for the catalytic photofixation of nitrogen. The effects of the combination of In2O3 with ZnIn2S4 on the crystallinity, microstructure, optical absorption, and charge transfer behavior of the In2O3/ZnIn2S4 hybrid photocatalysts were investigated. Benefiting from the synergistic effects of the photogenerated vacancies and a step-scheme charge separation mechanism, the In2O3/ZnIn2S4 hybrid photocatalyst exhibited significantly enhanced catalytic activity compared to those of bare In2O3 and pure ZnIn2S4, and an optimized 50 wt% In2O3/ZnIn2S4 hybrid sample was found to exhibit superior catalytic activity for the photofixation of N2, fixing 18.1 ± 0.77 mg·L−1 of ammonia after exposure to simulated sunlight for 2 h. Crucially, the results of trapping experiments and electron paramagnetic resonance investigation to identify the active species confirmed that the catalytic nitrogen photofixation performance was highly correlated with the presence of •CO2− radicals rather than photogenerated electrons, especially when methanol was used as a hole scavenger. In summary, the reported In2O3/ZnIn2S4 hybrid photocatalysts exhibit both stability and high activity for the photofixation of N2, making them promising catalysts for sunlight-driven artificial N2 fixation.