Fabrication of the Medium-Entropy Oxide/Carbon Composite with a Hollow Microstructure by Using a Soybean Polysaccharide Microsphere Template for the Oxygen Evolution Reaction

Medium-entropy oxides (MEOs) are a series of promising oxygen evolution reaction (OER) electrocatalysts due to lattice distortion and the synergistic effect of discrepant active sites. However, it is still a challenging issue to develop a facile route to fabricate MEO with a rational morphology and composition. Biomass materials are promising templates to synthesize nanostructured electrocatalysts, as their components and structures can reconstitute and form an unusual microstructure during the pyrolysis process. In this work, dissolved soybean polysaccharide with microsphere morphology is used as a template and reductant to synthesize a CoNiCu/C precursor via a hydrothermal process. Then, the precursor is oxidized to realize a medium-entropy oxide/carbon [(CoNiCu)O/C] composite with a unique hollow microstructure. Due to the advantages of rich active sites in the hollow nanostructure and the synergistic effects of multiple components, the (CoNiCu)O/C composite shows pleasant performance in catalyzing the OER, which needs an overpotential of 360 mV to support a 100 mA cm^-2 current density. This work demonstrates a promising route to design efficient OER electrocatalysts by using a biomass template.