Low-Temperature Molten Salt Synthesis for Ligand-Free Transition Metal Oxide Nanoparticles

High specific surface area, clean surface, and high intrinsic activity are vital for high-performance heterogeneous catalysts. Unfortunately, currently available synthetic methods can hardly meet all these demands. Herein, we propose a facile and general approach for the rapid synthesis of ligand-free metal oxide nanoparticles (NPs) in low-temperature molten salts. Because of the low reaction temperature (<150 °C) and quick process (∼1 min), the as-prepared metal oxide NPs possess ultrasmall particle sizes (<15 nm), low crystallinity structures, and most importantly clean surface, making them highly desirable for heterogeneous catalysis. As a demonstration for how valuable the low-temperature molten salt approach is for catalytic application, the as-prepared Ni–Fe–Ox NPs show outstanding oxygen evolution reaction (OER) activity (with a low overpotential of 226 mV at 10 mA cm–2), placing them among the best OER electrocatalysts.