Potential-Dependent Kinetics and Reaction Pathways of Low-Potential Furfural Electrooxidation with Anodic H Production.

The low-potential furfural electrooxidation reaction (FFOR) on copper-based catalysts provides a novel pathway to upgrade biomass and produce H simultaneously on anode. Herein, a series of oxide-derived copper catalysts (OD-Cu-x, x represents electroreduction time) with distinct Cu/Cu ratios and residual content of lattice oxygen are successfully constructed by tuning in-situ electroreduction time. When applied for FFOR, the OD-Cu-600 with a Cu/Cu ratio of 83.3% shows the Faradaic efficiency of 96.1% for furoic acid (FA) and 97.4% for H, which can be achieved at a lowest potential of 0.081 V versus RHE at 10 mA cm in continuous 10 cycles, outperforming the state-of-art Cu-based catalysts reported so far. Detailed characterization and density functional theory (DFT) calculations prove that the moderate coverage (25% based on DFT models) of Cu(OH) surface species generated by Cu during the electrooxidation process endows the optimal furfural molecule adsorption and activation. Moreover, this potential-dependent coverage of surface OH can promote the kinetics of *H transfer to the Cu surface, allowing the H evolution from the anode. The Cu/Cu ratio (83.8%) and suitable applied potential windows (0 to 0.4 V RHE) are both responsible for the co-production of FA and H with high intrinsic activity and efficient H atom utilization.