Activity origin and alkalinity effect of electrocatalytic biomass oxidation on nickel nitride

Electro-oxidation of 5-hydroxymethylfurfural（HMFOR） is a promising green approach to realize the conversion of biomass into value-added chemicals.However,considering the complexity of the molecular structure of HMF,an in-depth understanding of the electrocatalytic behavior of HMFOR has rarely been investigated.Herein,the electrocatalytic mechanism of HMFOR on nickel nitride（Ni3 N） is elucidated by operando X-ray absorption spectroscopy（XAS）,in situ Raman,quasi in situ X-ray photoelectron spectroscopy（XPS）,and operando electrochemical impedance spectroscopy（EIS）,respectively.The activity origin is proved to be Ni2+δN（OH）ads generated by the adsorbed hydroxyl group.Moreover,HMFOR on Ni3 N relates to a two-step reaction:Initially,the applied potential drives Ni atoms to lose electrons and adsorb OH-after 1.35 VRHE,giving rise to Ni2+δN（OH）ads with the electrophilic oxygen;then Ni2+δN（OH）ads seizes protons and electrons from HMF and leaves as H2 O spontaneously.Furthermore,the high electrolyte alkalinity favors the HMFOR process due to the increased active species(Ni2+δN（OH）ads) and the enhanced adsorption of HMF on the Ni3 N surface.This work could provide an in-depth understanding of the electrocatalytic mechanism of HMFOR on Ni3 N and demonstrate the alkalinity effect of the electrolyte on the electrocatalytic performance of HMFOR.