Electrochemical synthesis of high entropy hydroxides and oxides boosted by hydrogen evolution reaction

Abstract

Conventional synthesis techniques for high entropy materials often require prolonged processes or the use of complex fabrication steps. Here, we report on a scalable method to synthesize high entropy hydroxide and oxide nanoparticles using electrochemical synthesis in an aqueous environment. The current density parameter was set to create a non-equilibrium condition where the hydrogen evolution reaction results in a turbulent environment facilitating the formation of nanoparticles within the electrolyte. Using this approach, we demonstrate the synthesis of both binary (Fe, Mn) and quinary (Fe, Mn, Ni, Ca, Mg) metal hydroxide and oxide nanoparticles. The chemical and microscopy analysis shows that the high entropy nanoparticles can be synthesized as a hydroxide without any post processing and as an oxide through a calcination process with atomic scale mixing of all elements. The synthesis of high entropy nanoparticles is important for applications targeting catalysis, energy storage and conversion, filtration, and environmental engineering. • Aqueous electrochemical synthesis of high entropy hydroxides under ambient conditions • Green and substrate-free nanoparticle synthesis using inexpensive metal salts • Fast transformation from metal hydroxides to metal oxides with calcination process • Ability to scale to industrially promising applications Ritter et al. report an electrochemical process for quick and scalable synthesis of high entropy hydroxide and oxide nanoparticles that avoids long synthesis times and high temperatures. The large variety of metal salt precursors allows for tuning of the composition for applications in catalysis, energy storage, and conversion.