Facile colloidal synthesis of transition metal (Co, Fe, and Ni)-added Ir-W NPs for HER in acidic electrolyte

Abstract

Alloying earth-abundant transition metals with iridium, one of the promising catalysts for the hydrogen evolution reaction (HER), is an effective way to reduce the usage of precious metal without sacrificing its catalytic activity. In particular, tungsten and early transition metals (Co, Fe, and Ni) are known to promote the inherent HER activity by modulating surface adsorption energy, but ternary alloy nanoparticles (NPs) of those elements and their universal synthetic strategy are not well-established yet. In this study, we synthesized a new iridium-based ternary alloy NP with tungsten and transition metals of cobalt, iron, and nickel (Ir-M-W, M = Co, Fe, and Ni) through colloidal synthesis. All the constituent metal elements were uniformly distributed over the particle, forming a homogeneous solid solution. The Ir-M-W NPs showed excellent catalytic activity and mass activity toward HER in an acidic electrolyte compared with the binary Ir-W NPs. In particular, the Ir-Co-W NPs exhibited the lowest overpotential (35.82 mV of overpotential to drive −10 mA cm−2) and the highest mass activity (3.98 A/mgIr) with 40 µg cm−2 of catalyst loading. Such superior catalytic HER performance could be achieved by the modulation of the surface electronic structure induced by the inclusion of transition metal.