S-Scheme 2D/2D Bi2MoO6/BiOI van der Waals heterojunction for CO2 photoreduction

Reducing CO2 to hydrocarbon fuels by solar irradiation provides a feasible channel for mitigating excessive CO2 emissions and addressing resource depletion. Nevertheless, severe charge recombination and the high energy barrier for CO2 photoreduction on the surface of photocatalysts compromise the catalytic performance. Herein, a 2D/2D Bi2MoO6/BiOI composite was fabricated to achieve improved CO2 photoreduction efficiency. Charge transfer in the composite was facilitated by the van der Waals heterojunction with a large-area interface. Work function calculation demonstrated that S-scheme charge transfer is operative in the composite, and effective charge separation and strong redox capability were revealed by time-resolved photoluminescence and electron paramagnetic resonance spectroscopy. Moreover, the intermediates of CO2 photoreduction were identified based on the in situ diffuse reflectance infrared Fourier-transform spectra. Density functional theory calculations showed that CO2 hydrogenation is the rate-determining step for yielding CH4 and CO. Introducing Bi2MoO6 into the composite further decreased the energy barrier for CO2 photoreduction on BiOI by 0.35 eV. This study verifies the synergistic effect of the S-scheme heterojunction and van der Waals heterojunction in the 2D/2D composite. (c) 2022, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Automated summary

Reducing CO2 to hydrocarbon fuels through solar irradiation is a promising approach for mitigating CO2 emissions and resource depletion. However, the catalytic performance is hindered by severe charge recombination and high energy barrier. In this study, a 2D/2D Bi2MoO6/BiOI composite was fabricated to enhance CO2 photoreduction efficiency. The composite showed efficient charge transfer, strong redox capability, and effective charge separation. The intermediates of CO2 photoreduction were identified, and the rate-determining step for CH4 and CO production was determined to be CO2 hydrogenation. Introduction of Bi2MoO6 decreased the energy barrier for CO2 photoreduction on BiOI. The study highlights the synergistic effect of the S-scheme heterojunction and van der Waals heterojunction in the 2D/2D composite.