Tuning the adsorption behaviors of non-noble electrocatalysts to boost valorization of 5-hydroxymethylfurfural

Nickel-based non-noble materials have been widely used as catalysts for a variety of electrosynthesis reactions due to their low cost and tunable surface properties. However, few of them perform well for the 5-hydroxymethylfurfural (HMF) oxidation reaction (HMFOR) due to their weak adsorption capacity for low-concentration reactants. In this work, Ox-NiCuOz derived from mixed metal oxide (NiCuOz) via anodic reconstruction is employed for the HMFOR, which remarkably outperforms Ox-NiCu(OH)(z) derived from NiCu-hydroxide (NiCu(OH)(z)). A series of ex/in situ investigations and theoretical calculations reveal that the adsorptions of HMF and intermediates are enhanced on the low-coordinated surface sites of Ox-NiCuOz, which facilitates the dynamic Ni-II/Ni-III transformation and hence boosts the HMFOR. In addition, Red-NiCuOz derived via cathodic reconstruction is employed for the HMF reduction reaction (HMFRR). As a result, a paired HMFOR/HMFRR electrolysis is conducted using Ox-NiCuOz//Red-NiCuOz as the electrode pair, simultaneously yielding value-added products of 2,5-furandicarboxylic acid (FDCA) and 2,5-bishydroxymethylfuran (BHMF) with a combined faradaic efficiency (FE) of nearly 150% at 2 V. This study provides not only a guideline for non-noble catalyst design towards organic electrosynthesis, but also a rational scenario of paired electrolysis for highly efficient biomass utilization.