Fabrication of Nanostructured Medium-Entropy Oxides/Carbon Composites with Rich O Vacancy by a Soybean Polysaccharide Template for Hydrogen Evolution Reaction

Highly efficient and durable electrocatalysts play a crucial role in promoting the hydrogen evolution reaction (HER). Among them, medium-entropy oxides (MEOs)-based electrocatalysts have attracted extensive attention due to the advantages of multiple principal components, lattice distortion, and a hysteresis diffusion effect. However, it is still challenging to design MEOs with rational structures and composition. In this work, soluble soybean polysaccharide (SSPS) is used as a template to fabricate an FeCoNiO_x/C composite. The crucial role of the SSPS template during the formation of FeCoNiO_x MEOs is analyzed, which is in favor of the forming of an O vacancy and nanoparticle morphology with a sphere-like array. Owning to the synergistic effect of multiple principal components, conductive carbon material, and defective crystallinity, the O vacancy-modified FeCoNiO_x/C composite has significantly superior electrocatalytic HER properties, which need a low overpotential of 61 mV to afford a 10 mA cm^–2 current density with a Tafel slope of 90.7 mV dec^–1. The FeCoNiO_x/C MEOs with superior electrocatalytic properties and facile fabrication provide a significant opportunity to constitute beneficial electrocatalysts for industrial application.