Hollow mesoporous nickel dendrites grown on porous nickel foam for electrochemical oxidation of urea

Abstract

The macroporous nickel foam (NF) with attached hollow mesoporous nickel dendrites (NF@p-Ni) was prepared through electrochemical deposition of copper-nickel dendrites on the NF (NF@CuNi) followed by selective removal of the copper cores. The deposition process under high cathodic current density in an acidic solution favored the formation of hydrogen bubbles which acted as a template for the subsequent growth of macroporous dendritic copper-nickel film with 10 μm scale pores. The copper appeared to play an important part in the growth of dendritic shape and hollow porous structure on the porous and conductive NF framework. In the electrochemical oxidation of urea, the NF@p-Ni electrode could offer abundant electroactive sites and porous channels for increasing the oxidation current density and efficiency compared to the NF@CuNi electrode. The NF@p-Ni electrode featuring macroporous catalyst layer of hollow dendrites on highly conductive NF framework expedited the charge-transfer reaction of urea electrooxidation and the evolution of gaseous products. Thus, the current density and efficiency of NF@p-Ni could reach 141 mA cm−2 and 82%, respectively, higher than those of NF@CuNi (110 mA cm−2 and 72%, respectively) in catalyzing the electrochemical oxidation of urea molecules at 0.60 V versus saturated calomel electrode.