Enhanced electro-oxidation of urea using Ni-NiS debris via confinement in carbon derived from glucose

Abstract

Confining nanoparticles in carbon materials is an efficient method to enhance the catalytic performance. In this work, nickel sulfide was encapsulated in carbon via calcining the mixture of mesoporous NiS2 nanospheres and glucose at 550 °C. NiS2 was not stable at high temperature, it would be spontaneously decomposed into NiS debris and partly reduced to metallic Ni. When used as catalyst for urea electro-oxidation, the Ni-NiS@C with core-shell structure exhibited superior catalytic performance. Although the carbon shell itself had no catalytic activity towards urea electro-oxidation, it had a great promoting effect. The confinement effect of carbon shell could effectively tune the electronic properties of Ni species, the good electrical conductivity of carbon could decrease electron-transfer resistance, and the existence of carbon could protect the nickel sulfide debris against severe aggregation. Moreover, carbon could promote the formation of metallic Ni which also played a significant role to improve urea electro-oxidation performance. Therefore, Ni-NiS@C exhibited much higher catalytic activity and stability towards urea electro-oxidation compared with NiS2 and NiS without carbon shell.