Co-deposition of Co–Ni alloy catalysts from an ethylene glycol system for the hydrogen evolution reaction

Abstract

The preparation of active, stable and low-cost non-noble electrocatalysts for the hydrogen evolution reaction (HER) using the electrochemical water splitting process is crucial for the promotion of sustainable energy. In this study, Co–Ni alloys with various Co contents are prepared using a galvanostatic method and the co-deposition behavior of Co²⁺ and Ni²⁺ in ethylene glycol (EG) is reported. These results indicate that the presence of additional Ni²⁺ species can accelerate the Co–Ni co-deposition process and Co²⁺ species in the system can inhibit the reduction of Ni²⁺. Moreover, the two effects are improved with an increase in Ni²⁺ or Co²⁺ species concentration in the EG system, respectively. Chronoamperometry records show that the Co–Ni electro-crystallization mechanism is one of 3D instantaneous nucleation and growth. Moreover, the Co–Ni alloy with 59.46 wt% Co exhibits high electrocatalytic activity for HER with an overpotential of 133 mV at 10 mA cm⁻² in 1 M KOH due to a high value of electrochemical active surface area (ECSA) (955.0 cm²). Therefore, the Co–Ni alloy electrocatalyst obtained from the EG system could be a promising candidate for practical hydrogen production.