A Non‐Macrocycle Thiolate‐Based Cobalt Catalyst for Selective O2 Reduction into H2O

Abstract The reduction of dioxygen to produce selectively H 2 O 2 or H 2 O is crucial in various fields. While platinum‐based materials excel in 4H + /4e − oxygen reduction reaction (ORR) catalysis, cost and resource limitations drive the search for cost‐effective and abundant transition metal catalysts. It is thus of great importance to understand how the selectivity and efficiency of 3d‐metal ORR catalysts can be tuned. In this context, we report on a Co complex supported by a bisthiolate N2S2‐donor ligand acting as a homogeneous ORR catalyst in acetonitrile solutions both in the presence of a one‐electron reducing agent (selectivity for H 2 O of 93 % and TOFi=3 000 h −1 ) and under electrochemically‐assisted conditions (0.81 V <η<1.10 V, selectivity for H 2 O between 85 % and 95 %). Interestingly, such a predominant 4H + /4e − pathway for Co‐based ORR catalysts is rare, highlighting the key role of the thiolate donor ligand. Besides, the selectivity of this Co catalyst under chemical ORR conditions is inverse with respect to the Mn and Fe catalysts supported by the same ligand, which evidences the impact of the nature of the metal ion on the ORR selectivity.