Abstract: Ni-W-P alloy deposits were prepared by electrodeposition and heat treatment at different temperatures. Cathodic polarization curves and electrochemical impedance spectroscopy were used to study the influence of heat treatment on the electrocatalytic activity of the electrodeposited Ni-W-P alloy for the hydrogen evolution reaction (HER). The results demonstrated that, after heat treatment at 200 ℃, Ni-W-P alloy electrodes exhibited the highest electrocatalytic activity for HER and the overpotential was lowered by 110 mV at 8.0 mA/cm2 compared with the Ni-W-P alloy without heat treatment. The electrochemical reaction resistance for HER of the Ni-W-P alloy heat-treated at 200 ℃ was 17.1 Ω•cm2 and its exchange current density was 4.0 times higher than that of the Ni-W-P alloy without heat treatment. The increase in electrocatalytic activity of Ni-W-P alloys can be attributed to the increase in the real surface area and the decrease in the apparent energy of activation. The surface morphology and microstructure of the Ni-W-P alloy electrode were characterized by differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy. The average grain size of Ni-W-P alloy annealed at 200 ℃ increased from 1.1 to 2.8 nm and its structure changed from amorphous to nano-crystalline.

Key words: electrodeposition, nickel, tungsten, phosphorus, alloy, heat treatment, electrocatalysis, hydrogen