Electrocatalytic Properties of Ni1+xFe3-x-yAyN (A = Mo, W): The Effect of Mo and W in the Oxygen Evolution and Hydrogen Evolution Reaction in Alkaline Media

Ni, Fe-based nitrides have been widely studied for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media, displaying electrocatalytic activities similar to Pt and other noble metal electrocatalysts. The incorporation of small amounts of Mo or W on these Ni, Fe-based nitrides is expected to have a significant effect on the electrocatalytic performance of these materials, especially for the HER activity. In this work, transition metal nitrides (TMNs) with the empirical formula Ni(1+x)Fe(3-x-y)A(y)N (A = Mo, W), were obtained in two steps: synthesis of the transition metal oxide precursors by an easy, one-pot sol-gel polymerization method followed by nitridation under ammonia atmosphere to obtain the final TMNs. Their HER and OER catalytic performances in alkaline electrolyte (0.1 M KOH solution) were studied and it was observed that the incorporation of small quantities of Mo or W in these Ni, Fe-based nitrides (Ni(1+x)Fe(3-x-y)A(y)N, where y = 0.1) results in improved HER and OER activities, especially in the TMN that contains W (i.e., Ni1+xFe2.9-xW0.1N), where the overpotentials were 348 mV for OER and 269 mV for HER. These values are lower than those obtained for Ni1+xFe3-xN, which are 395 mV for OER and 368 mV for HER.