Enhanced Anodic 5‐Hydroxymethylfurfural Oxidation towards Efficient Overall CO2 Electrolysis

Electrocatalytic reduction of CO2 into value‐added chemicals provides an appealing approach to mitigating the carbon‐emission issues. However, the kinetically sluggish anodic oxygen evolution reaction (OER) not only consumes a large part of the electricity, but also produces O2 of low value, thus severely limiting the economy of overall CO2 electrolysis. Herein, we developed a biomass upgrade‐coupled CO2 reduction reaction (CO2RR) strategy that 5‐hydroxymethylfurfural oxidation reaction (HMFOR) was substituted for the traditional OER to selective produce high value‐added 2,5‐furanodiformic acid (FDCA) rather than O2 in the anode side of the overall CO2 electrolysis. A Ni foam‐supported sea urchin‐like NiCo2O4 anode (NiCo2O4@NF) was successfully fabricated with a high Faradaic efficiency of 97.3% for FDCA in HMFOR. In‐situ electrochemical impedance spectroscopic and Raman spectroscopic measurements revealed that the Ni2+ ↔ Ni3+ transformation with favored adsorption of OH– promotes HMFOR. Moreover, a two‐electrode cell featuring anodic HMFOR and cathodic CO2RR was assembled to simultaneously produce FDCA and formic acid. Compared with the traditional CO2RR‐OER couple, the energy requirement was significantly reduced by 22.9% by the CO2RR‐HMFOR couple. Furthermore, an efficient solar‐driven electrocatalytic CO2RR‐HMFOR system was established with excellent performance, demonstrating the viability of the coupling strategy.