Ultrafine IrRu Nanoparticles toward Efficient Oxygen Evolution Reaction in Acidic Media

Abstract

Proton exchange membrane water electrolyzers (PEMWEs) are capable of mass-producing green hydrogen with renewable and wave-trough electricity, but confront the challenge of the lack of advanced electrocatalysts to accelerate sluggish oxygen evolution reaction (OER). Herein, we report the synthesis of ultrafine IrRu alloy nanoparticles (1.6 ± 0.3 nm) by coprecipitation of IrCl3, RuCl3, and HCOONa in water to allow Ir3+ and Ru3+ to be well dispersed and enclosed in the matrix of crystalline HCOONa, followed by heat treatment of HCOONa to reduce Ir3+ and Ru3+. Remarkably, the overpotential of IrRu toward acidic OER at 10 mA cm–2 is merely 230 and 194 mV at 51 and 204 μgIrRu cm–2, respectively. The high electrochemically active surface area (ECSA) of 577.1 m2 g–1 and high specific activity (SA) of 22.7 μA cm–2 at 1.45 V vs RHE would contribute to the exceptional OER activity. In addition, the electron transfer from Ir to Ru in IrRu should significantly boost the OER activity according to X-ray photoelectron spectroscopy (XPS). IrRu also shows an excellent stability during 10 h of a chronopotentiometry (CP) test at 10 mA cm–2. Eventually, the high OER activity of IrRu was verified in a PEMWE.

Engineering Iridium-Based Oxygen Evolution Reaction Electrocatalysts for Proton Exchange Membrane Water Electrolyzers

“…Most bimetal alloys for OER involve the alloying Ir with other metals (M), e.g., Fe, Ni, Co, Ag, W, Os, Rh, Ru, etc. ,− For instance, Ir-coated Pd nanocube with unique concave surface (Pd@Ir c-nc) and flat surface (Pd@Ir f-nc) structures were controlled deposited by Lee and co-workers . In Figure e,f, the unique structure of Pd@Ir c-nc was proved by high-angle annular dark-field scanning TEM combined with energy-dispersive X-ray (STEM-EDX) mappings.…”

Nanoelectrocatalysts for Anodic Oxygen Evolution in Acid: A Review

“…Meanwhile, some metals are more thermodynamically stable when mixed together. , At present, alloying is considered a feasible approach to further tune catalytic properties. Based on this, Sun et al successfully synthesized ultrafine IrRu alloy nanoparticles by coprecipitation and heat treatment. Due to the transfer of Ir to Ru electrons in the catalyst, the OER activity is significantly improved and the catalyst can run stably for more than 10 h.…”

Ce-Modified Flowerlike NiFe-MOF Nanostructure Based on Ion Competitive Coordination for Enhancing the Oxygen Evolution Reaction

“…11−13 At present, Ru, Ir, and their oxides are generally considered as the mainstream catalysts for the OER. 14,15 However, the rarity and high cost of these noble metals cannot fulfill the increasing demand for energy. Therefore, how to design earth-abundant catalysts with both good catalytic performance and lower price is an interesting topic currently.…”

“…One is the hydrogen evolution reaction (HER) on the cathode, while the other is the oxygen evolution reaction (OER) on the anode. , Owing to the complex four-electron transfer process, the OER process usually requires a higher reaction activation energy compared with the HER. Thereupon, the catalytic activity of OER catalysts is an essential factor that affects the performance of overall water splitting. − At present, Ru, Ir, and their oxides are generally considered as the mainstream catalysts for the OER. , However, the rarity and high cost of these noble metals cannot fulfill the increasing demand for energy. Therefore, how to design earth-abundant catalysts with both good catalytic performance and lower price is an interesting topic currently …”