A coupled electrocatalytic system with reduced energy input for CO2 reduction and biomass valorization

Abstract

Coupling the cathodic electrochemical CO₂ reduction (eCO₂RR) with the anodic electrochemical 5-hydroxymethylfurfural oxidation reaction (HMFOR) is an appealing approach to co-produce value-added chemicals and simultaneously lower the energy input, while the main challenge is to develop effective electrocatalysts for eCO₂RR and HMFOR. Inspired by the techno-economic analysis, we herein report a coupling system for economical formate generation and biomass valorization by concurrent cathodic eCO₂RR and anodic HMFOR. Single Cu atom doped Bi (Cu₁Bi) and NiCo layer doubled hydroxides (NiCo LDHs) are used as the cathodic and anodic catalysts, respectively. Due to the accelerated water dissociation, the Cu₁Bi cathode catalyst demonstrated remarkably high activity (j_formate > 1 A cm⁻²) for formate conversion as well as robust stability (200 mA cm⁻² for 45 h). Meanwhile, the NiCo LDH anode displays high activity for HMF electrooxidation to 2,5-furandicarboxylic acid with a faradaic efficiency of over 95% at low potential. Consequently, the paired eCO₂RR-HMFOR system reduces the electricity input for the eCO₂RR-to-formate conversion to ∼3493 kW h per tonne of formate, corresponding to 22.9% in energy saving compared to the conventional eCO₂RR (∼ 4528 kW h per tonne of formate). This study offers an appealing route for CO₂ reduction and biomass valorization with low energy consumption.