Controlled synthesis of CoVP as robust electrocatalysts for water, seawater and urea oxidation

Abstract

Urea electrolysis has more advantages in energy saving and environmental protection as well as wastewater treatment. A series of CoVM (M = P, S and Se) catalytic materials with a nanosphere morphology composed of nanoneedles were successfully synthesized by one-step hydrothermal and tube furnace phosphating process. Based on the principle of electronic regulation, the polyvalent state of V can effectively provide the electronic and environmental structure required for Co, the catalytic activity of the electrode was significantly improved by increasing the charge transfer of the electrode. CoVP electrode shows excellent and efficient catalysis in the anodic reaction of water, seawater and urea electrolysis. At the current density of 10 mA cm−2, it only needed the overpotential of 270 mV for oxygen evolution reaction (OER) and only needed potential of 1.30 V for urea oxidation reaction (UOR). Experimental results show that the increased activity is attributed to the rapid charge transfer rate, the exposure of more active sites and the enhanced conductivity due to the synergistic catalysis of CoP and V3P. Density functional theory (DFT) calculation shows that the CoP material exhibits higher urea adsorption energy, which promotes catalysis. The V3P material shows a higher density of states near the Fermi level, indicating that it has better conductivity. The synergistic catalysis of the two enhanced the catalytic activity of the CoVP material. This study provides a new idea for the synthesis of catalytic electrode materials in the anodic oxidation aspect of urea electrolysis, and provides a further understanding for the improvement of catalytic performance of relatively non-toxic catalysts.