High-efficiency oxygen evolution catalysts: composite hexagonal structure SrCo1-yNiyO3-δ/Sr9Ni7O21

Abstract

Transition metal perovskite oxides are regarded as ideal catalysts for the oxygen evolution reaction (OER) owing to the high tunability of the B-site active elements. Among them, SrCoO3 has been widely studied due to its high theoretical catalytic performance, but incomplete oxidation of the B-site elements results in poor intrinsic activity. Herein, we prepared a series of SrCo1-xNixO3-δ (x = 0-0.5) catalysts for alkaline OER using a simple sol-gel method and optimized their catalytic performance by modulating the Co/Ni ratio and annealing temperature (950 ℃ and 1050 ℃). Among the series, SrCo0.6Ni0.4O3-δ (annealed at 950 ℃) with a composite hexagonal structure (SrCo1-yNiyO3-δ/Sr9Ni7O21, y = 0.1-0.2) exhibited the best OER activity, achieving an overpotential of 321 mV at 10 mA cm-2 (1 M KOH). The introduction of Ni ions and the presence of Sr₉Ni₇O₂₁ not only enhance the Co4+/Co3+ and Ni3+/Ni2+ ratios, but also promote the generation of more highly oxidative oxygen species (O22-/O-). Additionally, the abundant Ni3+ surface facilitates the formation of highly active NiOOH phase during OER, leading to a further reduction in the overpotential (after 1000 CV cycles, the overpotential on the nickel foam electrode decreased by 45 mV).