Preparation of a self-supported nickel–aluminum–cobalt phosphating electrode and its electrocatalytic performance in total water decomposition

Abstract

In order to improve the performance of electrocatalytic hydrogen evolution of electrocatalytic materials, nickel aluminum layered double hydroxide (Ni–Al LDH) was prepared by hydrothermal synthesis, and then nickel aluminum layered double oxide (Ni–Al LDO) was formed by heat treatment of Ni–Al LDH. Subsequently, NAC-545 was obtained by the addition of the Co element in the Ni–Al LDO using a vapor cation exchange method at 545 °C, and then phosphorization was carried out via CVD at low temperature. According to the physical characterization results, the phase composition and morphology will be completely different at different phosphorization temperatures. The electrochemical test results showed that the self-supported cobalt nickel aluminum 400 °C phosphide (SS NAC P-400) composed of Ni₂P and NiP₂ showed the best electrochemical performance, and the hydrogen evolution overpotential was 121.4 mV and 144.9 mV at 10 mA cm⁻² and 20 mA cm⁻², respectively. At 50 mA cm⁻² and 100 mA cm⁻², the oxygen evolution overpotential was 220 mV and 270 mV, and the lowest Tafel slope was 78.7 mV dec⁻¹ for the HER and 42.6 mV dec⁻¹ for the OER. The charge-transfer resistance is only 12.2 Ω. As a fully hydrolysable electrode, a current density of 10 mA cm⁻² can be reached only at 1.669 V. After a 12 h stability test, the voltage shows a small range of attenuation.