Ni/TiO ₂ heterostructures derived from phase separation for enhanced electrocatalysis of hydrogen evolution and biomass oxidative upgrading in anion exchange membrane electrolyzers

The construction of heterostructures is an effective strategy to enhance electrocatalysis for hydrogen evolution reactions (HERs) and biomass oxidative upgrading. In this work, a Ni/TiO₂ heterostructure prepared by a phase-separation strategy was adopted as a bifunctional electrocatalyst for HERs and biomass oxidation in alkaline media. Due to the optimized hydrogen adsorption energetics as well as the interfacial water structure and hydrogen bond connectivity in the electrical double layer, Ni/TiO₂ exhibited high activity for HERs with an overpotential of 28 mV at 10 mA cm^-2 and good durability at 1000 mA cm^-2 for over 100 h in an anion exchange membrane (AEM) electrolyzer. In addition, Ni/TiO₂ showed high catalytic performance for the oxidation of biomass-based platform compound 5-hydroxymethylfurfural (HMF) to high-value added compound 2,5-furandicarboxylic acid (FDCA). Continuous production of FDCA with a yield >95% was achieved in the AEM electrolyzer for over 50 h. The superior HMF oxidation performance on the Ni/TiO₂ heterostructure compared to Ni resulted from stronger HMF adsorption, lower Ni³⁺-O formation potential, longer Ni³⁺-O bond and smaller Ni crystal size.