High-efficient electrocatalytic CO2 reduction to HCOOH coupling with 5-hydroxymethylfurfural oxidation using flow cell

Among various products from electrocatalytic CO₂ reduction (CO₂ER), HCOOH is highly profitable one. However, the slow kinetics of anodic oxygen evolution reaction lowers overall energy efficiency, which can be replaced by an electro-oxidation reaction with low thermodynamic potential and fast kinetics. Herein, we report an electrolysis system coupling CO₂ER with 5-hydroxymethylfurfural oxidation reaction (HMFOR). A BiOCl–CuO catalyst was designed to sustain CO₂ER to HCOOH at partial current density of 500 mA/cm² with FE_HCOOH above 90% and 700 mA/cm² with FE_HCOOH above 80%. In situ and ex situ x-ray absorption fine structure was used to capture the structure transform of BiOCl–CuO into metallic Bi and Cu during CO₂ER process, and the presence of CuO will promote this transformation which are supported by DFT calculations. Coupling HMFOR with CO₂ER, we realize both FE_HCOOH and FE_FDCA above 95% simultaneously, providing new prospects vista for the electrosynthesis of value-added products from paired system.