Engineering the Morphology and Electronic Structure of NiCo₂O₄ to Boost the Electrocatalytic Oxidation of...

Electrocatalytic biomass conversion using green electricity is regarded as an important strategy to meet the requirement of sustainable development. NiCo₂O₄ electrodes with different morphologies and electronic structures were fabricated by changing the precipitants used in the solvothermal process, and applied in the electrocatalytic 5-hydroxymethylfurfural oxidation (HMFOR). The experimental and theoretical calculation results showed NiCo₂O₄ nanosheets (NCO-Ns) with low Co/Ni ratio exhibited larger adsorption energy towards HMF and superior intrinsic catalytic activity in HMFOR, while NiCo₂O₄ nanoneedles (NCO-Nn) with larger electrochemical active surface areas presented faster electron transfer kinetics and enhanced catalytic performance for 50 mM HMF with a higher conversion rate (99.9 %), 2,5-furanodicarboxylic acid (FDCA) selectivity (98.6 %) and faraday efficiency (98.6 %). It indicated that compared with NCO-Ns, NCO-Nn providing more active sites was kinetically favorable for improving HMFOR efficiency. In-situ electrochemical Raman investigation revealed that in strong alkaline media, NiOOH formed by the electrochemical reconstruction of NiCo₂O₄ surface served as the main active species in HMFOR, and an indirect oxidation mechanism was elucidated. This work established the relationship between the electrocatalytic performance of a catalyst and the surface morphology and electronic structure in HMFOR, provided a new idea for improving the electrocatalytic activity of a catalyst, and supported it experimentally.