Janus structure Ir–Ir3Ce@IrO2 nanocrystals as excellent bifunctionality catalysts for acidic overall water splitting

Abstract

Enhancing the catalytic performance of iridium (Ir)-based catalysts for water electrolysis under acidic conditions presents a significant challenge. This difficulty primarily arises from the substantial energy barriers associated with the four-electron–proton coupled oxygen evolution reaction (OER) at the anode and the two-electron transfer hydrogen evolution reaction (HER) at the cathode. This study successfully synthesized a novel type of Ir–Ir₃Ce@IrO₂ nanoparticles supported on defective carbon materials (DCMs; Ir–Ir₃Ce@IrO₂/DCMs) using freeze-drying and conversion methods. Notably, the catalyst core features a unique Janus structure comprising metal and alloy components. This catalyst demonstrates exceptional acidic OER activity, overall water-splitting catalytic performance, and high stability. Experimental results indicate that the Ir–Ir₃Ce@IrO₂/DCMs electrocatalyst delivers an ultralow overpotential of 210 mV at 10 mA cm⁻² for OER in 0.5 M H₂SO₄. Both structural characteristics and theoretical calculations suggest that Ir–Ir₃Ce@IrO₂/DCMs facilitate charge redistribution owing to various factors, including the alloying of precious metals and rare earth alloys, the Janus structure, and heterogeneous interfaces. The Ir–Ir₃Ce@IrO₂/DCMs || Ir–Ir₃Ce@IrO₂/DCMs electrolyzer can operate in acidic electrolytes for >40 h. This study presents a viable strategy to address the issues of instability and low efficiency associated with Ir-based OER electrocatalysts for acidic overall water splitting.