Electrocatalyst of two-dimensional CoP nanosheets embedded by carbon nanoparticles for hydrogen generation and urea oxidation in alkaline solution

Abstract Hydrogen (H2) producing from the electrolysis of water at cathode is limited by the sluggish kinetics of oxygen evolution reaction (OER) at anode. It is essential to search a facile anodic reaction to replace OER in the hydrogen generation process. Urea oxidation reaction (UOR) is an alternative strategy to instead of OER in the water splitting reaction. Based on this, we successfully prepare two-dimensional (2D) CoP nanosheets embedded by carbon nanoparticles (CoP/C) composites as bifunctional catalysts to achieve hydrogen evolution reaction (HER) at cathode and UOR at anode simultaneously. Benefiting from the presence of carbon particles and 2D sheet structure of CoP in the composites, the contact area of electrolyte/electrode is enlarged, the exposed active sites are increased, and charge transfer rate is improved. As the anode and cathode catalysts in a two-electrode system with continuous electrolyte supplementation by a flow reactor, the CoP/C-3 composite only need 1.40 V to reach the current density of 10 mA cm-2 in the 1 M KOH electrolyte with 0.1 M urea. This study on hydrogen generation and urea oxidation at a low potential provides a promising method to prepare bifunctional catalysts for practical applications.