Unlocking the Potential of Mechanochemical Coupling : Boosting the Oxygen Evolution Reaction by Mating Proton Acceptors with Electron Donors

The oxygen evolution reaction (OER) is the bottleneck of many sustainable energy conversion systems, including water splitting technologies. The kinetics of the OER is generally sluggish unless precious metal-based catalysts are used. Perovskite oxides have shown promise as alternatives to these expensive materials. However, for several perovskites, including SrCoO_3−δ, the rate-limiting step is proton-transfer. In this study, it is shown that such a kinetic limitation can be overcome by coupling those perovskites with MoS₂ mechanochemically. By studying composites of SrMO_3−δ (M = Co, Fe, Ti) and MoS₂, the role that the formed heterointerfaces play in enhancing the activity is investigated. Mechanochemically mating SrCoO_3−δ and MoS₂ increases the mass activity toward OER by a factor of ten and led to a Tafel slope of only 37 mV dec⁻¹. In contrast, combining MoS₂ with SrFeO_3−δ or SrTiO_3−δ, two materials whose OER is not limited by proton-transfer, does not result in an improvement of the performance. The experimental measurements and first-principle calculations reveal that the MoS₂ at the MoS₂@SrCoO_3−δ heterointerfaces is both an electron and a proton acceptor, thereby facilitating deprotonation of the perovskite and resulting in faster OER kinetics.