Plasmonic versus Dielectric Mie Resonance-Mediated Photocatalytic Reverse Water–Gas Shift Reaction on Copper-Based Nanocubes

The conversion and storage of solar energy as a chemical fuel are crucial technologies for the future of clean energy. Photocatalysis by the reverse water–gas shift (RWGS) reaction is a promising method to achieve this objective. This article investigates the photocatalytic effect of visible light on copper-based nanocatalysts for the RWGS reaction. Through ultraviolet–visible extinction spectroscopy, X-ray diffraction, photoreactor studies, scanning transmission electron microscope imaging, operando transient reflection, and density functional theory calculations, we demonstrate that the copper-based photocatalysts can enhance the reaction rate for RWGS reaction via dielectric Mie resonance in the cuprous oxide phase or plasmonic Mie resonance in the metallic copper phase depending on the reaction conditions. Both copper phases demonstrate remarkable performance, achieving up to a 21-fold increase in reaction rates under visible light irradiation. Additionally, the apparent quantum efficiency on these photocatalysts is 1–3 orders of magnitude higher than values on hybrid plasmonic photocatalysts previously reported in the literature. These findings suggest that copper-based Mie resonator photocatalysts have significant promise for solar energy conversion and carbon dioxide valorization through green chemical reaction engineering.