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

Abstract

Reducing CO 2 to hydrocarbon fuels by solar irradiation provides a feasible channel for mitigating excessive CO 2 emissions and addressing resource depletion. Nevertheless, severe charge recombination and the high energy barrier for CO 2 photoreduction on the surface of photocatalysts compromise the catalytic performance. Herein, a 2D/2D Bi 2 MoO 6 /BiOI composite was fabricated to achieve improved CO 2 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 CO 2 photoreduction were identified based on the in situ diffuse reflectance infrared Fourier-transform spectra. Density functional theory calculations showed that CO 2 hydrogenation is the rate-determining step for yielding CH 4 and CO. Introducing Bi 2 MoO 6 into the composite further decreased the energy barrier for CO 2 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. The S-scheme 2D/2D Bi 2 MoO 6 /BiOI van der Waals heterojunction accelerates charge separation, enhances the redox capability of photoexcited electron-hole pairs, and decreases the energy barrier of the CO 2 photoreduction reaction, contributing to a high CO and CH 4 yield rate.