High-entropy alloy stabilized active Ir for highly efficient acidic oxygen evolution

Abstract

We proposed a conceptual and experimental breakthrough in serving the nanoscale high-entropy alloy as substrates to stabilize the active Ir with ultra-low loading by using Fe, Co, Ni and Ru as stabilizing structural elements, achieving efficient and acid-stable OER performance. • HEA were used as substrates to stabilize the active Ir with ultra-low loading. • Ultra-small FeCoNiIrRu HEA NPs were in situ synthesized in CNFs. • FeCoNiIrRu HEA NPs exhibited thermodynamic induced phase evolution. • FeCoNiIrRu/CNFs exhibit low overpotential of 241 mV (10 mA cm −2 ). • OER performances were optimized by changing the metal compositions and calcination temperatures. We reported a conceptual and experimental breakthrough in serving the nanoscale high-entropy alloy (HEA) as substrates to stabilize the active Ir with ultra-low loading by using Fe, Co, Ni and Ru as stabilizing structural elements. The ultra-small FeCoNiIrRu HEA nanoparticles were in situ synthesized in electrospun carbon nanofibers (CNFs), and it exhibited thermodynamic induced phase evolution, as revealed by in situ characterization. The FeCoNiIrRu/CNFs exhibit exciting oxygen evolution reaction (OER) activity with low overpotential of 241 mV at 10 mA cm −2 and high mass activity of 205 mA mg -1 Ir+Ru . The hysteretic diffusion effect of HEA strongly inhibits the metal leaching and dissolution, leading to the excellent durability. The OER performance can be optimized by changing the metal compositions and calcination temperatures. In situ Raman spectra reveal the formation of OH and superoxo (OO) intermediates on HEA NP surfaces. Theoretically calculation indicate that the electron density redistribution in FeCoNiIrRu NPs occurs from low electronegative elements (Fe, Co, and Ni) to high electronegative ones (Ir, Ru) and it make the Ir more active to simultaneously promote the conversion of *OOH and generation of O 2 .