Rational Design of Rhodium–Iridium Alloy Nanoparticles as Highly Active Catalysts for Acidic Oxygen Evolution

Abstract

The oxygen evolution reaction (OER) is pivotal for renewable energy conversion and storage devices, such as water electrolyzers and rechargeable metal–air batteries. However, the rational design of electrocatalysts with suitably high efficiencies and stabilities in strongly acidic electrolytes remains a significant challenge. Here, we show the demonstration of sub-10 nm, composition-tunable Rh–Ir alloy nanoparticles (NPs) prepared using a scalable microwave-assisted method as superior acidic OER catalysts. The OER activities showed a volcano-shaped dependence on Ir composition, with Ir-rich NPs (Ir ≥ 51%) achieving better OER performance than pure Ir NPs, as reflected by lower overpotentials and higher mass activities. Most significantly, Rh22Ir78 NPs achieved a maximum mass activity of 1.17 A mg–1 Ir at a 300 mV overpotential in 0.5 M H2SO4, which corresponds to a 3-fold enhancement relative to pure Ir NPs, making it one of the most active reported OER catalysts under acidic conditions. Density functional theory calculations reveal that owing to the synergy of ensemble and electronic effects by alloying a small amount of Rh with Ir, the binding energy difference of the O and OOH intermediates is reduced, leading to faster kinetics and enhanced OER activity. Furthermore, Rh–Ir alloy NPs demonstrated excellent durability in strongly acidic electrolyte. This work not only provides fundamental understandings relating to composition–electrochemical performance relationships but also represents the rational design of highly efficient OER electrocatalysts for applications in acidic media.

Exclusive Strain Effect Boosts Overall Water Splitting in PdCu/Ir Core/Shell Nanocrystals

“…Thec urrent overpotential and mass activity of PdCu/Ir/C represent one of the best level of the Ir-based OER electrocatalysts in acidic conditions yet reported (Figure 2e &T able S1). [29][30][31][32][33][34][35][36][37][38] Stability,a so ne of the most important issues of electrocatalysts,i sa lso evaluated by accelerated durability tests (ADTs) and chronoamperometry (CP) measurement. After 2000 CV cycles between 1.40 and 1.65 V(vs.RHE) before IR correction at an accelerated scan rate of 50 mV s À1 ,t he overpotential of PdCu/Ir/C at acurrent density of 10 mA cm À2 only increases 5mV (Figure 2f).…”

Recent Progress in Electrocatalysts for Acidic Water Oxidation

“…[ 103,104 ] The Rh x Ir (100− x ) NPs display efficient OER catalytic performance with the decrease of Rh content (Rh, Rh 73 Ir 27 , Rh 49 Ir 51 , and Rh 22 Ir 78 ). [ 105 ] The overpotential of Rh 22 Ir 78 could reach 292 mV at 10 mA cm −2 in 0.5 m H 2 SO 4 , which is lower than Ir NPs and other Rh x Ir (100− x ) samples. A series of precious‐ and nonprecious‐based alloy catalysts, such as Ru‐M binary OER catalysts (where M = Cr, Pd, Re, Ni, Cu, Ir, and Co) are used for the electrolytic water oxidation.…”

Amorphous/Crystalline Heterostructured Cobalt‐Vanadium‐Iron (Oxy)hydroxides for Highly Efficient Oxygen Evolution Reaction

“…[5] The design of high-performance catalysts is an important step for efficient OER. Previously, iridium (Ir)-and ruthenium (Ru)based materials [6,7] are often used for OER catalysts, but the scarcity and high cost of these noble metals limit their wide applications. [8,9] Therefore, the development of earth-abundant and inexpensive electrocatalysts, which can reduce the overpotential of OER process, has long been the challenges for practical applications.…”