On the Activity and Selectivity of 5-Hydroxymethylfurfural Electrocatalytic Oxidation over Cation-Defective Nickel Hydroxides

Electrocatalytic oxidation as a promising route to produce value-added products from biomass-derived organics has received increasing attention in recent years. However, the efficient conversion of concentrated feedstock solutions with high selectivity and Faradaic efficiency (FE) remains challenging. Herein, we report a cation-defective Ni-based electrocatalyst derived from the surface reconstruction of the NiCo Prussian blue analogue (NiCo PBA) in alkaline media for the efficient oxidation of biomass-derived organics in a high concentration solution. Taking 5-hydroxymethylfurfural (HMF) as an example, the NiCo PBA can deliver a satisfactory catalytic performance in terms of high HMF conversion (97%), selectivity to 2,5-furandicarboxylic acid (98%), and FE (100%), even at a concentration as high as 100 mM. Theoretical calculations suggest that the cation defects not only promote the fast conversion of Ni(OH)2 to electrochemically active NiOOH under anodic potential but also enhance the adsorption of HMF onto the active sites and accelerate the spontaneous chemical oxidation. This study provides deep insights into the structural evolution of PBA-based catalysts and reveals the pivotal factor that affects the performance of electrocatalytic oxidation, paving the way to further develop advanced electrocatalysts for efficient oxidation reactions with a high concentration.