IrO₂–ZnO Composite Nanorod Array as an Acid-Stable Electrocatalyst with Superior Activity for the Oxygen Evolution Reaction

Abstract

An IrO 2 −ZnO composite nanorod array with distinct morphological features was successfully fabricated through a facile method via a simple acid−base reaction, followed by a postcalcination process. A modulation in the annealing treatment time (t) generated the variation in morphology, at a constant temperature (600 °C), and the nanorod-like growth on the surfaces was revealed at t ≥ 3 h. Especially, the IrO 2 −ZnO composite nanorod array exhibited superior OER catalytic activities (e.g., a potential of 1.481 V at 10 mA cm −2 (vs RHE) and a Tafel slope of 42.9 mV dec −1 ). Moreover, there was no apparent potential shift with robust long-term cycling stability under acidic conditions, which were much better than those of IrO 2 and commercial iridium (cIr) and comparable with those of the previously reported outstanding Ir-based OER catalysts. Considering that the nanorod array was fabricated with the loading of the Zn metal component, which showed generally low catalytic activity and poor durability, this study suggests a promising strategy with an extended synthetic methodology for preparing Zn-mixed metal oxides as highly efficient electrocatalysts.

Atomically dispersed Ru sites on MOF-derived NC-ZnO for efficient oxygen evolution reaction in acid media

“…The Tafel slope has been widely investigated in relation to the rate-determining step for OER electrocatalysis. [52][53][54][55] The chemical stages involved in the mechanism of the OER on the electrode's active metal oxide are oen proposed to involve the following in acidic medium:…”

Enhancement of ZnO@RuO2 bifunctional photo-electro catalytic activity toward water splitting

“…More specifically, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) rule the energy storage system through electrocatalytic water splitting; the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) control fuel cells; and the ORR and OER are predominant in electrochemically rechargeable metal–air batteries ( Li et al, 2019 ). Due to the slow kinetics, the main problem in the electrochemical reactions, with a large overpotential and low round-trip efficiency as consequences, the development and implementation of highly efficient electrocatalysts are needed for HER, OER, and ORR to increase the reaction rate and the efficiency of the overall system ( Jiang et al, 2019 ; Li et al, 2019 ; Jin et al, 2022 ). A plethora of developed electrocatalysts can be used to improve individual electrocatalytic reactions.…”

“…Since HER, OER, and ORR occur in completely different potential windows, few commercially available catalysts can act as multifunctional electrocatalysts; more specifically, the best OER catalyst usually has poor HER activity, while the best ORR catalyst does not have the best OER catalysis performance, and vice versa ( Li et al, 2019 ). Currently, the best electrocatalysts for HER and ORR are Pt-based materials, while RuO 2 and IrO 2 exhibit the best OER electrocatalytic activity ( Li et al, 2019 ; Devadas et al, 2020 ; Xie et al, 2020 ; Jin et al, 2022 ; Milikić et al, 2023 ). However, despite their high catalytic activity toward OER and their potential for use as efficient bifunctional HER/OER catalysts, both RuO 2 and IrO 2 are limited by their poor long-term stability, natural scarcity, and high price ( Guan et al, 2018 ; Liang et al, 2020 ).…”

“…Therefore, interest is increasing in the development of low-cost and more stable efficient bi- or even trifunctional catalysts. So far, various composites with precious metal oxides such as RuO 2 and IrO 2 , and abundant materials, such as ZnO, MoO 3 , WO 3 , and g-C 3 N 4 , have been developed and tested as catalysts ( Tariq et al, 2020 ; Wang et al, 2021a ; Jin et al, 2022 ; Nur et al, 2022 ).…”