Improving the Oxygen Evolution Reaction: Exsolved Cobalt Nanoparticles on Titanate Perovskite Catalyst.

Perovskites are an important class of oxygen evolution reaction (OER) catalysts due to highly tunable compositions and adaptable characteristics. However, perovskite-based catalysts can have limited atom utilization efficiency due to large particle size, resulting in low mass activity. Herein, Cobalt nanoparticles are exsolved from La 0.2+2x Ca 0.7-2x Ti 1-x Co x O 3 perovskite and applied in OER. Upon reduction in the 5% H 2 /N 2 atmosphere at 800 °C for 2 h, the Co exsolved perovskite catalyst (R-LCTCo0.11) exhibits optimal OER performance. The mass activity of R-LCTCo0.11 reaches ≈1700 mA mg -1 at an overpotential of 450 mV, which is 17 times and 3 times higher than that of LCTCo0.11 (97 mA mg -1 ) and R-Mix (560 mA mg -1 ) catalysts respectively, surpassing the benchmark catalyst RuO 2 (42.7 mA mg -1 of oxide at η = 470 mV). Electrochemical impedance spectroscopy (EIS) data reveals that R-LCTCo0.11 has the lowest charge transfer resistance (R ct  = 58 Ω), demonstrating the highest catalytic and kinetic activity for OER. Furthermore, this catalyst shows high stability during an accelerated durability test of 10 h electrolysis and 1000 cycles cyclic voltammetry (CV). This work demonstrates that nanoparticle exsolution from a doped perovskite is an effective strategy for improving the atom utilization efficiency in OER.