“…In heterogeneous electrocatalysis of water splitting, however, metal oxides (MO 2 , M = Ir, Ru) or oxy-hydroxides (MO(OH), M = Ni, Fe, Co, etc.) are the state-of-the-art for OERs [ 9 , 10 , 11 ], while metals (Rh, Pt, Ir) are suitable for HERs [ 12 , 13 ] (also non-noble [ 2 , 14 , 15 , 16 ]), regulated by the oxophilicity character of the surfaces [ 17 , 18 ]. Basically, those metal nanoparticles are initially prepared before the used of carbon black to lower the metal content, which does not enable the maximization of the electrocatalytic performance and minimization of the loss of active sites during the long-term operation.…”