Fast joule heating synthesis of NiCoFeCrMo high-entropy alloy embedded in graphene for water oxidation.

High-entropy alloys (HEAs) are considered as considerable candidate for electrocatalytic water splitting. The main holdback locates in fabricating well-defined HEAs with moderate electronic structure and uncovering the structural evolution during the reaction process. Herein, we successfully synthesized NiCoFeCrMo HEA-nps by an ultrafast joule heating method for highly efficient oxygen evolution reaction (OER). The optimal graphene incorporated NiCoFeCrMo HEA nanoparticles (HEA-nps) exhibits finely distributed nanoparticles with average size of 17.49 nm and uniformly distribution of all the five elements, which displays the outstanding OER performance with a low onset potential and only requires the 260 mV (vs RHE) to achieve the current density of 10 mA cm−2. X-ray absorption fine structure (XAFS) demonstrates that the high valence Cr and Mo can directly regulate the local structure of HEA-nps, which significantly promoted the intrinsic activity of high active species. This work not only provides a design strategy related to the high valence elements injection for HEAs, but also uncovers the structural evolution of HEAs during OER process. [Display omitted] • NiCoFeCrMo HEA were successfully synthesized by fast Joule heating method. • Multi-electron Cr and Mo elements have regulated the local electronic structure. • The intrinsic mechanism of each element in HEAs during the reaction process has been clarified. [ABSTRACT FROM AUTHOR]