Facile syntheses and in-situ study on electrocatalytic properties of superaerophobic CoxP-nanoarray in hydrogen evolution reaction

Transition metal phosphides (TMPs) have drawn considerable attention as a result of their high catalytic activities for the hydrogen evolution reaction (HER). In this work, a three-dimensional (3D) porous CoxP ordered nanoarray structure was successfully deposited on nickel foam (denoted as NF@CoxP, 1 <_ x <_ 2) via a strategy involving facile gamma ray irradiation and annealing without the use of reducing agent. By modulating the annealing temperature in the synthetic process for NF@CoxP, 3D porous ordered nanoarray composites exhibiting inherently superhydrophilic and superaerophobic properties were produced, the physical properties were confirmed with the use of various in-situ test techniques. The superhydrophilic properties of NF@CoxP help to increase the rate of ion transfer between the CoxP and the electrolyte. Additionally, in-situ verification of the superaerophobic properties showed that they are beneficial for quick release of the generated H2 bubbles from the surface of NF@CoxP electrode, which was analyzed by coupling a 3D confocal microscope with an electrochemical workstation for the first time. As expected, when the resulting NF@CoxP composites were employed as catalyst electrodes for the HER in a 1 M KOH electrolyte, the 3D porous ordered nanoarray structure exhibited an overpotential of 272 mV at the current density of 200 mA cm-2, which was much higher than those of commercial 20%Pt/C catalysts. Therefore, the synthetic strategy for producing NF@CoxP composites with 3D porous ordered nanoarray structures showed high potential for application in the HER.