FeCoNi-Based Alloy Coatings as Low Overpotential Electrocatalysts for Alkaline Water Electrolysis

Developing efficient, stable and low-cost electrocatalysts is a viable approach to solve the current energy crisis. It is found that increasing the surface area of the electrodes can effectively promote the electrocatalytic efficiency. Herein, the atmospheric plasma spraying (APS) technology was used to prepare FeCoNi-Ni₃C alloy coating by adding Ni₃C powder to FeCoNi powder with an equal molar ratio. After mechanical mixing, the atomic ratios of Ni₃C in the powder are 25 %, 50 %, and 75 %, respectively. The results prove that the pores on the surface of the coating have increased after Ni₃C doping, which can provide more active sites in the electrocatalytic process to promote the electrocatalytic reaction. By controlling the proportion of Ni₃C, the porosity of the coating surface can be effectively regulated. The results suggested that in 1.0 M KOH electrolyte and 10 mA cm^-2, the FeCoNi coating shows an overpotential of 191 and 277 mV for HER and OER, respectively, the HER overpotential of 50 at % Ni₃C FeCoNi-Ni₃C coating is 105 mV, and the OER overpotential is 212 mV. It is worth noting that the 50 at % Ni₃C FeCoNi-Ni₃C coating has a low Tafel slope of 45.78 mV dec^-1 (HER) and 44 mV dec^-1 (OER). Meanwhile, the attenuation of the overpotential of the 50 at % Ni₃C FeCoNi-Ni₃C coating after the stability test is almost negligible, indicating that the prepared catalyst has excellent electrocatalytic stability. Furthermore, the 50 at.% Ni₃C FeCoNi-Ni₃C coating catalyst has a low potential of 1.664 V at 10 mA cm^-2 in a water-splitting system. This work provids a new idea for designing inexpensive electrocatalysts.