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

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.