Phase Transition Kinetics via Operando Monitoring Electro-Oxidation Reaction of 5-Hydroxymethylfurfural on Amorphous Nickel Oxyhydroxide

Abstract

Nickel-based electrocatalysts have been studied for the electrochemical 5-hydroxymethylfurfural oxidation reaction (HMFOR) to produce 2,5-furan-dicarboxylic acid. Their catalytic activity is suggested to be related to structural changes and hydrogen atom transfer pathways. Here, we developed an efficient electrocatalyst by introducing amorphous NiOOH through electro-driven dual-ion leaching from phosphorized nickel–molybdenum oxide nanoarrays. Operando X-ray absorption spectroscopy and Raman spectroscopy reveal that the amorphous NiOOH catalyst undergoes a rapid phase transformation to form Ni(OH)2 states during the HMFOR, whereas a conventional NiOOH catalyst transitions to Ni(OH)2 via a mixed phase of NiOOH/Ni(OH)2. Operando infrared spectroscopy analysis under chronopotentiometry additionally provides insights into the electro-kinetics, supporting the generation of water through the combination of OH– and released proton during HMFOR. This indicates that the coordination environments near the active Ni element influence the dehydrogenation kinetics of the active nickel species. This study provides insights into the kinetics of HMFOR associated with the structural transition for the design of Ni-based electrocatalysts.