Smart Control of Composition for Double Perovskite Electrocatalysts toward Enhanced Oxygen Evolution Reaction

Double perovskites have emerged as efficient candidates for catalyzing the electrochemical oxygen evolution reaction (OER). Smart control of the composition of a B-site ordered double perovskite can lead to improved catalytic performance. By adopting a facile co-doping strategy, the OER-active elements are simultaneously introduced into the B-site and B'-site of a B-site-ordered double perovskite (A₂ BB'O₆ ), leading to an enhancement of the exposed reactive sites and an optimum surface chemical state. As a result, a model system built from the substitution of Co for Mo and Fe in the Sr₂ FeMoO_6-δ double perovskite (with a composition of Sr₂ Fe_0.8 Co_0.2 Mo_0.6 Co_0.4 O_6-δ ) shows significantly enhanced OER activity in alkaline media compared with the host material, requiring an overpotential of 345 mV to reach a 10 mA cm^-2 current density (catalyst loading≈0.232 mg_cat  cm^-2 _GEO ) and a cell voltage of 1.57 V to afford the same current density for the overall water splitting when coupled with a Pt/C cathode (catalyst loading≈2 mg cm^-2 ). It also demonstrates excellent electrochemical stability. The generalizability of the compositional control methodology has also been demonstrated in double perovskites incorporating transition metals other than Co (e.g., Ni).