“…[32] Also, MOFs are composed of inorganic subunits, such as layers, clusters, chains, or 3D arrangements, and are strongly bonded to organic binders with complex groups (phosphonates, carboxylates, N-containing compounds), resulting in a 3D hybrid framework. [33,34] These characteristics result in the excellent improvement in the onset potential, half-slope potential (E 1/2 ), and durability of ORR performance. [35][36][37] However, MOF materials generally present lower ORR current density, which would be ascribed to their less electrochemical active surface areas.…”