Strain-induced in situ formation of NiOOH species on Co–Co bond for selective electrooxidation of 5-hydroxymethylfurfural and efficient hydrogen production

It is an efficient strategy to replace sluggish water oxidation with a thermodynamically more favorable reaction, electrochemical selective conversion of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), to promote hydrogen production. High selectivity and Faradaic efficiency (>99%) for the conversion of HMF to FDCA and simultaneous hydrogen production were achieved under 220 mV overpotential on NiCo₂O₄ electrode. The addition of HMF decreased the anode overpotential, and the amount of generated hydrogen through coupling with HMF oxidation is 8.16 times higher than that of water splitting. Operando Raman identified that NiOOH as the main active species for selective electrooxidation of HMF to FDCA. Operando EXAFS demonstrates that the crystal-strain induced formation of NiOOH from Co–Co bond and such a crystal strain could be further enhanced by the electric field for the in situ formation of more NiOOH. The accelerated reaction pathway was confirmed by operando electrochemical infrared (EC-IR) and DFT calculations.