Tuning Cu/Cu₂ O Interfaces for the Reduction of Carbon Dioxide to Methanol in Aqueous Solutions

Artificial photosynthesis can be used to store solar energy and reduce CO₂ into fuels to potentially alleviate global warming and the energy crisis. Compared to the generation of gaseous products, it remains a great challenge to tune the product distribution of artificial photosynthesis to liquid fuels, such as CH₃ OH, which are suitable for storage and transport. Herein, we describe the introduction of metallic Cu nanoparticles (NPs) on Cu₂ O films to change the product distribution from gaseous products on bare Cu₂ O to predominantly CH₃ OH by CO₂ reduction in aqueous solutions. The specifically designed Cu/Cu₂ O interfaces balance the binding strengths of H* and CO* intermediates, which play critical roles in CH₃ OH production. With a TiO₂ model photoanode to construct a photoelectrochemical cell, a Cu/Cu₂ O dark cathode exhibited a Faradaic efficiency of up to 53.6 % for CH₃ OH production. This work demonstrates the feasibility and mechanism of interface engineering to enhance the CH₃ OH production from CO₂ reduction in aqueous electrolytes.