Nickel core-iridium oxide shell catalysts prepared by galvanic replacement method for enhancing oxygen evolution reaction in proton exchange membrane water electrolysis

Oxygen evolution reaction (OER) catalysts for proton exchange membrane water electrolysis (PEMWE) typically rely on precious metals. However, they are expensive and their synthetic procedure is complicated. To overcome the challenges and further enhance OER activity, new nickel core-iridium oxide shell (Ni@IrO₂) catalysts are suggested with galvanic replacement synthetic method. By this rapid and simple method, the amount of used iridium (Ir) is considerably reduced and their catalytic performance is well preserved. The Ni@IrO₂ catalysts are synthesized in just 2 h by one-pot system. When 0.5 mM Ir precursor that is its optimal concentration is used, Ni@IrO₂ catalysts have dense and stable Ir shell morphology, which improves stability of Ni core and OER activity. Evaluations of PEMWEs including such optimally determined Ni@IrO₂ catalyst demonstrate that cell voltage of 1.69 V is achieved at 1 A cm⁻² with low loading amount of Ir (0.16 mg_Ir cm⁻²) and degradation rate (0.258 mV h⁻¹ over 100 h). Based on that, it is proved that by the adoption of new galvanic replacement method, excellent Ni@IrO₂ catalysts are prepared and the performance of PEMWEs using the catalyst is improved.