Well-designed efficient charge separation in 2D/2D N doped La2Ti2O7/ZnIn2S4 heterojunction through band structure/morphology regulation synergistic effect

Abstract

La2Ti2O7, a layered perovskite material, has attracted much attention in photocatalytic hydrogen production due to its high stability and non-toxic. Combing La2Ti2O7 with narrow band gap semiconductors to construct 2D/2D heterojunction is a facile strategy to improve photocatalytic activity. In this work, we first report a novel 2D/2D N–La2Ti2O7/ZnIn2S4 heterojunction via in-situ growth of abundant well-dispersed ZnIn2S4 nanosheets on the N–La2Ti2O7 nanosheets surface. Experimental results show the optimized 2D/2D N–La2Ti2O7/ZnIn2S4 sample exhibits the best light-driven H2 evolution activity, which is nearly 5.2 and 1.7 times higher than that of pristine ZnIn2S4 and 2D/2D La2Ti2O7/ZnIn2S4 samples, respectively. This is due to the unique 2D/2D heterojunction produces high-speed charge transfer channels, thus significantly enhancing photo-carriers separation and migration efficiency. Meanwhile, DFT calculations confirm nitrogen doping forms impurity energy states at the top of valence band, thus narrowing the band gap of La2Ti2O7, considerably inhibiting electron-hole pair recombination. Further the microstructures and charge separation properties are analyzed by SEM, PL, and DFT calculations to reveal the structure-activity relationship of hetero-structure and the synergistic mechanism of each functional component. This report will hopefully provide a practical strategy for designing heterojunction composite for high light-driven hydrogen evolution rate.