Molten-Salt-Protected Pyrolysis for Fabricating Perovskite Nanocrystals with Promoted Water Oxidation Behavior

The high overpotential for triggering the oxygen evolution reaction (OER) severely hampers promotion of the overall efficiency for water electrolysis, which significantly restricts implementation of commercial electrocatalytic hydrogen production. Toward exploring advanced OER catalysts with both high efficiency and low cost, transition metal compounds have been regarded as promising alternatives to replace precious metal-based catalysts, among which the cobalt-based materials, especially LaCoO3 perovskites, are highly attractive owing to their tunable electronic structure, relatively high activity, and superior stability. However, the harsh reaction environments for the fabrication of perovskites often result in micrometer-scale particles with limited surface sites, and modulation of electronic structures is also required to be further optimized. In this work, we proposed a molten-salt-protected pyrolysis (MSPP) route to convert the amorphous nanoparticle precursors to LaCoO3 nanocrystals with tunable Fe doping, during which the molten salts could not only act as an effective reaction medium to avoid interparticle sintering but also induce enrichment of surface Co3+ ions with high catalytic activity. Theoretical and experimental analyses indicate that Fe doping could significantly modulate the electronic structure of LaCoO3, resulting in enhanced Co–O covalency and facile charge transfer behavior during the OER. With the above merits, remarkable OER performance with ultralow overpotential, high catalytic current density, small Tafel slope, outstanding intrinsic OER activity, and superior operational stability can be synergistically achieved for the Fe-doped LaCoO3 nanocrystals, making the perovskite nanocatalyst a promising candidate for electrochemical water splitting.