The oxygen evolution reaction (OER) is the bottleneck in direct solar and electrocatalytic water splitting cells, and rechargeable aqueous metal-air batteries. Improving the cost-efficiency of these devices requires development of efficient and cheap oxygen evolving catalysts. A good catalyst material should fulfil several important criteria: the composition and structure should be stable at conditions of interest, it should be able to conduct electrons from the active site, and it should be sufficiently active to catalyze water oxidation to oxygen.

We explore three different oxide classes comprising 1^st row transition metals 1) pristine and doped Co and Ni oxyhydroxides (ox-hy), 2) pristine and doped perovskite oxides ABO₃ (A is the earth-alkali or lanthanide metal and B the 1^st row transition metal) and 3) pristine and doped αMnO₂ as catalysts for the oxygen evolution reaction in neutral to alkaline pH. The emphasis in the analyses is placed on the three most important performance parameters: structural stability, catalytic activity and electronic conductivity.

1. For the ox-hy class we systematically investigate the influence of the nano-scale structure going from 3D catalysts to 2D nanosheets; we examine different edge and terrace terminations, as well as the effect of all stable metal dopants on the performance at pertinent potentials. We identify Fe doped Co, and V, Fe, Ru, Ir and Rh doped Ni ox-hys, as the best catalyst materials, out of which Rh doped Ni ox-hys exhibits the highest activity. Furthermore, we find that the electronic conductivity changes with the nature and valence of the dopant atom, which in turn depends on potential.

2. For the perovskite oxides, we identify Fe⁴⁺, Co³⁺(IS), Ni³⁺ and Mn³⁺/Mn⁴⁺ pairs as electronically conductive species and distinguish among three different conduction types: intrinsic conductance (Fe⁴⁺, Co³⁺(IS) and Ni³⁺), electron polaron hoping in Mn compounds with mixed valences and conduction via oxygen 2p and metal 3d holes in the valence band.

3. We investigate whether the performance of αMnO_2, which according to many studies is the most active MnO₂ polymorph, can be further improved by means of doping. Through a systematic approach we identify Pd doped αMnO₂ to be a stable and highly active catalyst for the oxygen evolution reaction.

This work was supported by the Horizon 2020 framework, grant number 646186.