“…28–30 We recently reported on the synthesis and OER activity of binary Co x Fe 3− x O 4 (0 < x < 1.75) 31 and ternary Co x Ni 1− x Fe 2 O 4 (0 < x < 1) 32 and CoV 2− x Fe x O 4 (0 < x < 2) 33 spinel-type nanoparticles, for which a distinct effect on the OER activity was observed, depending both on the distinct metal and the metal concentration. Theoretical studies suggest that atomic doping produces lattice strain, which affects the electronic structure of the material surface, 34 thereby increasing the electrochemical performance of M x Co 3− x O 4 nanoparticles in OER catalysis. In addition, metal doping leads to an optimization of the binding energy of intermediates adsorption during the OER, especially of *O, *OH and *OOH, respectively.…”