Engineering the Morphology and Electronic Structure of NiCo2O4 to Boost the Electrocatalytic Oxidation of 5-Hydroxymethylfurfural

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.