Electrocatalytic oxidation of urea in alkaline solution using nickel/nickel oxide nanoparticles derived from nickel-organic framework

Abstract

Nickel-organic framework (NiOF) compound with layered structure was prepared by solvothermal synthesis using nickel chloride and bezenedicarboxylic acid precursors. NiOF could be converted into nickel with a face-centered cubic structure and nickel oxide with a cubic rock-salt crystal structure after heating above 425°C in air atmosphere. The organic units played a key role in the formation of well-dispersed nickel/nickel oxide nanoparticles. Primary particle size could be decreased by lowering the calcination temperature. Electrophoresis allowed for depositing a thin layer of nickel/nickel oxide nanoparticles on the skeleton of macroporous nickel foam (NF) as a catalyst electrode for electrooxidation of urea. Nickel/nickel oxide nanoparticles derived from NiOF at 425°C possessed large amounts of redox active sites (Ni2+/Ni3+), and thus was capable of enhancing the current density and efficiency in urea electrolysis. NF substrate with unique macroporous conductive structure exhibited electrocatalytic behavior towards urea electrolysis and allowed for rapid transport of electron, electrolyte, and gaseous products. Therefore, coating of nickel/nickel oxide nanoparticles on NF provided a possible way for further enhancing the electrocatalytic ability of electrode in urea electrolysis, making it favorable for large-scale applications.