Well-designed efficient charge separation in 2D/2D N doped La_2Ti_2O_7/ ZnIn_2S_4 heterojunction through band structure/morphology regulation synergistic effect

摘要

La_2Ti_2O_7,a layered perovskite material,has attracted much attention in photocatalytic hydrogen production due to its high stability and non-toxic.Combing La_2Ti_2O_7 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-La_2Ti_2O_7/ZnIn_2S_4 heterojunction via in-situ growth of abundant well-dispersed ZnIn_2S_4 nanosheets on the N-La_2Ti_2O_7 nanosheets surface.Experimental results show the optimized 2D/2D N-La_2Ti_2O_7/ZnIn_2S_4 sample exhibits the best light-driven H_2 evolution activity,which is nearly 5.2 and 1.7 times higher than that of pristine ZnIn_2S_4 and 2D/2D La_2Ti_2O_7/ZnIn_2S_4 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 La_2Ti_2O_7,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.