High-entropy heterostructures modulated by oxyphilic transition metals for efficient oxygen evolution reaction

The unique heterostructure and multimetallic synergy of high-entropy materials (HEMs) provide them with excellent catalytic properties for the oxygen evolution reaction (OER). Research on OER electrocatalysis in HEMs is mainly focused on the variation of transition metal composition. Little attention has been paid to the changes in the kinetic behaviour of these HEMs, let alone the control mechanisms based on these changes in kinetic behaviour. Here, we demonstrate for the first time a strategy to regulate the kinetic behaviour by reconfiguring the catalyst to form HEA-HEO heterostructures through the addition of a fifth oxyphilic metal element, x (x = Sc, Ti, V, Cr). Metal elements with higher oxyphilic activity have a higher oxygen content in the catalyst during the induced reconstruction process. However, the larger oxidation component also led to unfavorable adsorption of intermediates of the OER process on the heterostructured HEA-HEO catalysts. Operando Raman analyses and real-time kinetic simulations show that the rate-determining step (RDS) on all surfaces of the FeCoNiMn-x catalysts is the formation of the reaction intermediate OOH* from adsorbed O*. On FeCoNiMnSc, FeCoNiMnTi, FeCoNiMnV, and FeCoNiMnCr, the activation energies for the formation of OOH* intermediates showed a decreasing trend. The work function of the FeCoNiMn-x catalyst in the density functional theory (DFT) calculations shows the same trend. In stability tests, FeCoNiMnCr showed a negligible loss of activity even after being exposed to an ultra-high current density of 500 mA cm-2 for 112 hours. This study opens up new ideas for oxophilic metals to induce structural strategies to modify high-entropy catalysts.