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Iridium metallene oxide for acidic oxygen evolution catalysis.

ABSTRACT: Exploring new materials is essential in the field of material science. Especially, searching for optimal materials with utmost atomic utilization, ideal activities and desirable stability for catalytic applications requires smart design of materials' structures. Herein, we report iridium metallene oxide: 1 T phase-iridium dioxide (IrO₂) by a synthetic strategy combining mechanochemistry and thermal treatment in a strong alkaline medium. This material demonstrates high activity for oxygen evolution reaction with a low overpotential of 197 millivolt in acidic electrolyte at 10 milliamperes per geometric square centimeter (mA cm_geo^-2). Together, it achieves high turnover frequencies of 4.2 s_UPD^-1 (3.0 s_BET^-1) at 1.50 V vs. reversible hydrogen electrode. Furthermore, 1T-IrO₂ also shows little degradation after 126 hours chronopotentiometry measurement under the high current density of 250 mA cm_geo^-2 in proton exchange membrane device. Theoretical calculations reveal that the active site of Ir in 1T-IrO₂ provides an optimal free energy uphill in *OH formation, leading to the enhanced performance. The discovery of this 1T-metallene oxide material will provide new opportunities for catalysis and other applications.

SUBMITTER: Dang Q

PROVIDER: S-EPMC8516950 | biostudies-literature | 2021 Oct

REPOSITORIES: biostudies-literature

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Iridium metallene oxide for acidic oxygen evolution catalysis.

Dang Qian Q Lin Haiping H Fan Zhenglong Z Ma Lu L Shao Qi Q Ji Yujin Y Zheng Fangfang F Geng Shize S Yang Shi-Ze SZ Kong Ningning N Zhu Wenxiang W Li Youyong Y Liao Fan F Huang Xiaoqing X Shao Mingwang M

Nature communications 20211014 1

Exploring new materials is essential in the field of material science. Especially, searching for optimal materials with utmost atomic utilization, ideal activities and desirable stability for catalytic applications requires smart design of materials' structures. Herein, we report iridium metallene oxide: 1 T phase-iridium dioxide (IrO<sub>2</sub>) by a synthetic strategy combining mechanochemistry and thermal treatment in a strong alkaline medium. This material demonstrates high activity for oxy ...[more]

PMID: 34650084

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Project description:Proton exchange membrane water electrolysis (PEMWE) is a promising technology to produce hydrogen directly from renewable electricity sources due to its high power density and potential for dynamic operation. Widespread application of PEMWE is, however, currently limited due to high cost and low efficiency, for which high loading of expensive iridium catalyst and high OER overpotential, respectively, are important reasons. In this study, we synthesize highly dispersed IrRu nanoparticles (NPs) supported on antimony-doped tin oxide (ATO) to maximize catalyst utilization. Furthermore, we study the effect of adding various amounts of Ni to the synthesis, both in terms of catalyst structure and OER activity. Through characterization using various X-ray techniques, we determine that the presence of Ni during synthesis yields significant changes in the structure of the IrRu NPs. With no Ni present, metallic IrRu NPs were synthesized with Ir-like structure, while the presence of Ni leads to the formation of IrRu oxide particles with rutile/hollandite structure. There are also clear indications that the presence of Ni yields smaller particles, which can result in better catalyst dispersion. The effect of these differences on OER activity was also studied through rotating disc electrode measurements. The IrRu-supported catalyst synthesized with Ni exhibited OER activity of up to 360 mA mgPGM -1 at 1.5 V vs RHE. This is ∼7 times higher OER activity than the best-performing IrO x benchmark reported in the literature and more than twice the activity of IrRu-supported catalyst synthesized without Ni. Finally, density functional theory (DFT) calculations were performed to further elucidate the origin of the observed activity enhancement, showing no improvement in intrinsic OER activity for hollandite Ir and Ru compared to the rutile structures. We, therefore, hypothesize that the increased activity measured for the IrRu supported catalyst synthesized with Ni present is instead due to increased electrochemical surface area.

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Iridium metallene oxide for acidic oxygen evolution catalysis.

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Iridium metallene oxide for acidic oxygen evolution catalysis.

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