Ni-exsolved nanoparticles from a titanium-based perovskite as efficient active sites for the OER in alkaline media

• La 0.4 Sr 0.4 Ti 0.94 Ni 0.06 O 3-y (LSTN) perovskite was successfully synthesized. • Exsolution led to the formation of Ni nanoparticles on the surface. • OER activity increases markedly after exsolution at 900°C. • The optimum electrocatalyst exhibits very high Ni-specific OER activity. Even though Ni-based catalysts are usually used for the anode and cathode in alkaline water electrolysis, their performance needs to be further enhanced. In the last few years exsolution of metal nanoparticles has emerged as a strategy to improve catalytic activity. However, few studies have used this strategy to improve the performance of electrocatalysts for alkaline water electrolysis. In this study, we report a highly active Ni-based electrocatalyst for the oxygen evolution reaction (OER) with ultra-low Ni loading, formed via Ni exsolution from La 0.4 Sr 0.4 Ti 0.94 Ni 0.06 O 3-y . This work evaluates the effect of the calcination and the reduction temperature on the crystal structure, surface composition, oxidation state and OER performance. Rietveld refinement confirmed the successful Ni incorporation into the perovskite, and HRTEM and EDX reveal the formation of ∼14 nm Ni/Ni-O nanoparticles on the surface after exsolution, which significantly enhances OER activity, achieving 2.1 mA cm −2 at 1.6 V, compared to only 0.07 mA cm −2 for the non-exsolved catalyst. The optimum electrocatalyst exhibits very high Ni-specific OER activity over 630 A g Ni -1 at 1.65 V vs RHE. The optimum electrocatalyst showed good stability in an AEM cell at 500 mA cm −2 and the cell potential remained steady at 2.12 V for 20 h. Therefore, this work proves the potential exsolution has as a strategy to improve the performance of mixed oxide for electrolysis in alkaline media.