The synthesis of Cr and P codoped NiMoO4 nanospheres as efficient catalyst for urea oxidation and oxygen evolution reaction

Abstract

The design of reasonable and efficient electrocatalysts is imperative in large scale water splitting applications. In this paper, NiMoO4 nanospheres doped with Cr and P were constructed by hydrothermal method and phosphating process as electrocatalysts for water splitting, and the doping of Cr and P effectively modulated the electronic structure, which led to an increase in the active sites and an increase in the intrinsic activity of each site. Notably, Cr/P–NiMoO4@NF presented excellent urea oxidation reaction (UOR) performance (1.312V @ 10 mA cm−2) and oxygen evolution reaction (OER) performance (overpotential 309 mV @ 10 mA cm−2) in electrolytes of 1 M KOH and 1 M KOH with 0.5 M urea because of the doping effect of Cr and P. The experimental analysis showed that the improvement of electrochemical performance was mainly reflected in the accelerated electron transfer rate, increased exposure of reaction sites and improved metal properties and so on. For Cr/P–NiMoO4@NF, after a long time UOR and OER stability test, some changes have taken place in the appearance of the sample, which increases the contact area and provides more active sites, making the catalytic performance of the sample have no too obvious attenuation. Density functional theory calculation shows that the Cr/P–NiMoO4 material exhibits higher urea adsorption energy, indicating that urea is preferentially adsorbed on its surface. The Cr/P–NiMoO4 material shows more state density near the Fermi level, indicating that the introduction of Cr and P enhances the conductivity of the Cr/P–NiMoO4 material. This work provides a novel idea for the research and exploitation of low cost and robust UOR and OER electrocatalysts.