“…3,4 Despite Ru and Ir (including their oxides) being ideal catalysts for the OER, their high-cost and poor stability not only hinder their commercial application but also lead to the development of cost-effective catalysts, such as transition metal compounds. [5][6][7] Among various catalysts, heterogeneous transition metal oxide (TMOs) and nitride (TMNs) catalysts, including NiO/ CoN, 8 Ni 3 Mo 3 N-MoO 2 -NiO, 9 and CoO/CoN, 10 have been reported as OER catalysts. 11,12 This is because the TMOs are suitable for water adsorption, 13 while TMNs exhibit better electronic conductivity than the transition metal oxides.…”