High entropy stabilizing lattice oxygen participation of Ru- based oxides in acidic water oxidation

Abstract

The development of high-performance oxygen evolution reaction (OER) electrocatalysts for water splitting, particularly in acidic media, remains a difficult challenge. In this work, a Ru-based high entropy oxide (HEO) catalyst, RuNiMoCrFeO_x nanoparticles (∼6 nm), loaded onto carbon nanotubes (CNTs) was synthesized by a solvent-free microwave method. By optimising its composition, we find that the RuNiMoCrFeO_x/CNT catalyst shows high performance in 0.5 M H₂SO₄, with the overpotential of the HEO being only 219 mV (better than the 280 mV of commercial RuO₂) at 10 mA cm⁻² and the Tafel slope reaching 47 mV dec⁻¹. It is worth noting that this high entropy oxide (HEO) can operate at a high current density of 100 mA cm⁻² for up to 100 hours. The isotopic gas detection and electron spin resonance (ESR) experiments show that the OER tends to proceed through the LOM, and the high conformational entropy stabilizes the involvement of lattice oxygen in acidic solutions.