“…[1][2][3] The OER is at hermodynamically andk inetically demanding process, because it involves four sequential proton-coupled electron-transfer steps and the formation of oxygen-oxygen bonding. In this context, considerable research efforts have recently been de-voted to the search for efficient and inexpensive OER catalysts comprising earth-abundant elements, including transitionmetal oxides, [8][9][10] hydroxides, [11][12][13] perovskites, [14,15] phosphates, [16,17] sulfides, [18,19] and recently reported phosphides. [4] Presently,r uthenium and iridium oxides( RuO 2 and IrO 2 )a re state-of-the-artO ER catalysts [5][6][7] and are particularly indispensable for water electrolysis in acidic solution.H owever, both Ru and Ir are expensive and have limited availability in the earth'sc rust, and therefore, it is not practical to deploy electrochemical devices containing RuO 2 or IrO 2 catalysts on av ery large scale commensurate with globald emand.…”