Highly effective IrxSn1−xO2 electrocatalysts for oxygen evolution reaction in the solid polymer electrolyte water electrolyser

Abstract

We developed an advanced surfactant-assistant method for the Ir_xSn_1−xO₂ (0 < x ≤ 1) nanoparticle (NP) preparation, and examined the OER performances by a series of half-cell and full-cell tests. In contrast to the commercial Ir black, the collective data confirmed the outstanding activity and stability of the fabricated Ir_xSn_1−xO₂ (x = 1, 0.67 and 0.52) NPs, which could be ascribed to the amorphous structure, good dispersion, high pore volume, solid-solution state and Ir-rich surface for bi-metal oxides, and relatively large size (10–11 nm), while Ir_0.31Sn_0.69 exhibited poor electro-catalytic activity because of the separated two phases, a SnO₂-rich phase and an IrO₂-rich phase. Furthermore, compared with highly active IrO₂, the improved durability, precious-metal Ir utilization efficiency and correspondingly reduced Ir loading were realized by the addition of Sn component. When the Ir_0.52Sn_0.48O₂ cell operated at 80 °C using Nafion® 115 membrane and less than 0.8 mg cm⁻² of the noble-metal Ir loading, the cell voltages we achieved were 1.631 V at 1000 mA cm⁻², and 1.821 V at 2000 mA cm⁻². The IR-free voltage at the studied current density was very close to the onset voltage of oxygen evolution. The only 50 μV h⁻¹ of voltage increased for the 500 h durability test at 500 mA cm⁻². In fact, these results are exceptional compared to the performances for OER in SPEWE cells known so far. This work highlights the potential of using highly active and stable IrO₂–SnO₂ amorphous NPs to enhance the electrolysis efficiency, reduce the noble-metal Ir loading and thus the cost of hydrogen production from the solid polymer electrolyte water electrolysis.