Creation of SnxNb1−xO2 solid solution through heavy Nb-doping in SnO2 to boost its photocatalytic CO2 reduction to C2+ products under simulated solar illumination

Abstract

Photocatalytic CO2 reduction driven by green solar energy could be a promising approach for the carbon neutral practice. In this work, a novel defect engineering approach was developed to form the SnxNb1−xO2 solid solution by the heavy substitutional Nb-doping of SnO2 through a robust hydrothermal process. The detailed analysis demonstrated that the heavy substitution of Sn4+ by a higher valence Nb5+ created a more suitable band structure, a better photogenerated charge carrier separation and transfer, and stronger CO2 adsorption due to the presence of abundant acid centers and excess electrons on its surface. Thus, the SnxNb1−xO2 solid solution sample demonstrated a much better photocatalytic CO2 reduction performance compared to the pristine SnO2 sample without the need for sacrificial agent. Its photocatalytic CO2 reduction efficiency reached ∼292.47 µmol/(g·h), which was 19 times that of the pristine SnO2 sample. Furthermore, its main photocatalytic CO2 reduction product was a more preferred multi-carbon (C2+) compound of C2H5OH, while that of the pristine SnO2 sample was a one-carbon (C1) compound of CH3OH. This work demonstrated that, the heavy doping of high valence cations in metal oxides to form solid solution may enhance the photocatalytic CO2 reduction and modulate its reduction process, to produce more C2+ products. This material design strategy could be readily applied to various material systems for the exploration of high-performance photocatalysts for the solar-driven CO2 reduction.