Synergistically optimizing the electrocatalytic performance of IrO2 with double doping and bi-directional strains for acidic oxygen evolution reaction

Abstract

Because of the strong acidic environment and oxidative conditions, realizing highly active and stable iridium (Ir)-based electrocatalysts toward oxygen evolution reaction (OER) in a proton exchange membrane (PEM) electrolyzer is still a big challenge to overcome. To solve this problem, a novel core–shell structured Tm_0.1Sb_0.2Ir_0.7O_x@TB-IrO_x nanocatalyst with bi-directional (shear and axial) strains was fabricated. It only needs a low overpotential of 192 mV (10 mA cm⁻²) for OER in acidic electrolytes with impressive stability, exceeding most recently reported Ir-based electrocatalysts. Moreover, Tm_0.1Sb_0.2Ir_0.7O_x@TB-IrO_x exhibits an exceptionally high mass activity of 3.36 A mg_Ir⁻¹ (η = 270 mV). The enhanced catalytic activity resulted from the introduction of Tm, causing the Ir 5d band center (ε_d) to be closer to the Fermi level, which was demonstrated by theoretical calculations and microscopy characterizations. Additionally, a PEM electrolyzer adopting a Tm_0.1Sb_0.2Ir_0.7O_x@TB-IrO_x nanocatalyst indicates efficiency stability for a span of 500 hours and a cell voltage of 2.01 V to achieve 2 A cm⁻².