Ethanol photosynthesis from CO2 and H2O via a formate intermediate pathway

Abstract

Photocatalytic CO2-to-ethanol conversion offers an interesting route for intermittent solar energy utilization. However, the performance is impeded by slow mass-transfer and high dimerization barrier (>1.0 eV) of *CO intermediates, coupled with a kinetic mismatch between the short-lived carriers and the 12 e⁻ reaction. Herein, we develop a Z-scheme Cuδ+O/floral-like BN photocatalyst that achieves CO2-to-ethanol conversion with near 100% selectivity. The photocatalyst utilizes the three-dimensional structure and alkaline surface of BN to concentrate CO2 and directs transfer of long-lived carriers to unsaturated Cu⁺ sites, stabilizing them for flexible electron donation to the π* orbital of CO2. Enhanced ethanol photosynthesis activity/selectivity stems from a new pathway: CO2 is first reduced to HCOOH at Cuδ+O sites, lowering the C–C coupling barrier to 0.44 eV. Liquid formate is then concentrated and protonated to C2 precursor, minimizing side reactions for high selectivity. Here, we show the feasibility of selective ethanol photosynthesis and uncovers a new formate intermediate pathway.