Alkali Metal Iridates as Oxygen Evolution Catalysts Via Thermal Transformation of Amorphous Iridium (oxy)hydroxides.

Mario Falsaperna; Rosa Arrigo; Frank Marken; Simon J. Freakley

doi:10.1002/cctc.202401326

Alkali Metal Iridates as Oxygen Evolution Catalysts Via Thermal Transformation of Amorphous Iridium (oxy)hydroxides.

Mario Falsaperna, Rosa Arrigo, Frank Marken, Simon J. Freakley

University of Salford

Research output: Contribution to journal › Article › peer-review

Abstract

Efficient water-splitting is severely limited by the anodic oxygen evolution reaction (OER). Iridium oxides remain one of the only viable catalysts under acidic conditions due to their corrosion resistance. We have previously shown that heat-treating high-activity amorphous iridium oxyhydroxide in the presence of residual lithium carbonate leads to the formation of lithium-layered iridium oxide, suppressing the formation of low-activity crystalline rutile IrO ₂. We now report the synthesis of Na-IrO _x and K-IrO _x featuring similarly layered crystalline structures. Electrocatalytic tests confirm Li-IrO _x retains similar electrocatalytic activity to commercial amorphous IrO ₂ ⋅ 2H ₂O and with increasing size of the intercalated cation, the activity towards the OER decreases. However, the synthesised electrocatalysts that contain layers show greater stability than crystalline rutile IrO ₂ and amorphous IrO ₂ ⋅ 2H ₂O, suggesting these compounds could be viable alternatives for industrial PEM electrolysers where durability is a key performance measure.

Original language	English
Article number	e202401326
Journal	ChemCatChem
Early online date	23 Aug 2024
DOIs	https://doi.org/10.1002/cctc.202401326
Publication status	E-pub ahead of print - 23 Aug 2024

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Acknowledgements

We are grateful to Dr J. Yang (College of International Education, ECUST, Shanghai, China) for providing us with the crystallographic model for KIrO\u2009\u22C5\u20090.6HO. We would also like to thank Johnson Matthey for providing us with precursors for our synthesis and for conducting ICP measurements on our samples. We thank Dr M. E. Schuster (Johnson Matthey) for carrying out the HR\u2010TEM measurements. Part of the illustrations in Scheme\u2005 1 were created using Chemix. 0.3 2 2

Funding

We are grateful for support from the UK Catalysis Hub funded by EPSRC grant reference EP/R026645/1. We are grateful to Diamond Light Source for providing instrument time and support for the B07 (SI35991) and B18 beamlines (SP33143\u20131). We want to thank Dr D. Morgan (Cardiff University, UK) for carrying out XPS work through the support of the EPSRC National Facility for X\u2010ray photoelectron spectroscopy (\u2018HarwellXPS\u2019, EP/Y023587/1, EP/Y023609/1, EP/Y023536/1, EP/Y023552/1 and EP/Y023544/1).

Funders	Funder number
Cardiff University	EP/Y023544/1, EP/Y023552/1, EP/Y023609/1, EP/Y023587/1, EP/Y023536/1
Cardiff University
Engineering and Physical Sciences Research Council	EP/R026645/1
Engineering and Physical Sciences Research Council

Keywords

amorphous iridium oxo-hydroxide
electrocatalysis
hydrothermal synthesis
iridium oxide
oxygen evolution reaction

ASJC Scopus subject areas

Catalysis
Physical and Theoretical Chemistry
Organic Chemistry
Inorganic Chemistry

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1002/cctc.202401326Licence: CC BY

Cite this

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title = "Alkali Metal Iridates as Oxygen Evolution Catalysts Via Thermal Transformation of Amorphous Iridium (oxy)hydroxides.",

abstract = "Efficient water-splitting is severely limited by the anodic oxygen evolution reaction (OER). Iridium oxides remain one of the only viable catalysts under acidic conditions due to their corrosion resistance. We have previously shown that heat-treating high-activity amorphous iridium oxyhydroxide in the presence of residual lithium carbonate leads to the formation of lithium-layered iridium oxide, suppressing the formation of low-activity crystalline rutile IrO 2. We now report the synthesis of Na-IrO x and K-IrO x featuring similarly layered crystalline structures. Electrocatalytic tests confirm Li-IrO x retains similar electrocatalytic activity to commercial amorphous IrO 2 ⋅ 2H 2O and with increasing size of the intercalated cation, the activity towards the OER decreases. However, the synthesised electrocatalysts that contain layers show greater stability than crystalline rutile IrO 2 and amorphous IrO 2 ⋅ 2H 2O, suggesting these compounds could be viable alternatives for industrial PEM electrolysers where durability is a key performance measure.",

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AU - Freakley, Simon J.

PY - 2024/8/23

Y1 - 2024/8/23

N2 - Efficient water-splitting is severely limited by the anodic oxygen evolution reaction (OER). Iridium oxides remain one of the only viable catalysts under acidic conditions due to their corrosion resistance. We have previously shown that heat-treating high-activity amorphous iridium oxyhydroxide in the presence of residual lithium carbonate leads to the formation of lithium-layered iridium oxide, suppressing the formation of low-activity crystalline rutile IrO 2. We now report the synthesis of Na-IrO x and K-IrO x featuring similarly layered crystalline structures. Electrocatalytic tests confirm Li-IrO x retains similar electrocatalytic activity to commercial amorphous IrO 2 ⋅ 2H 2O and with increasing size of the intercalated cation, the activity towards the OER decreases. However, the synthesised electrocatalysts that contain layers show greater stability than crystalline rutile IrO 2 and amorphous IrO 2 ⋅ 2H 2O, suggesting these compounds could be viable alternatives for industrial PEM electrolysers where durability is a key performance measure.

AB - Efficient water-splitting is severely limited by the anodic oxygen evolution reaction (OER). Iridium oxides remain one of the only viable catalysts under acidic conditions due to their corrosion resistance. We have previously shown that heat-treating high-activity amorphous iridium oxyhydroxide in the presence of residual lithium carbonate leads to the formation of lithium-layered iridium oxide, suppressing the formation of low-activity crystalline rutile IrO 2. We now report the synthesis of Na-IrO x and K-IrO x featuring similarly layered crystalline structures. Electrocatalytic tests confirm Li-IrO x retains similar electrocatalytic activity to commercial amorphous IrO 2 ⋅ 2H 2O and with increasing size of the intercalated cation, the activity towards the OER decreases. However, the synthesised electrocatalysts that contain layers show greater stability than crystalline rutile IrO 2 and amorphous IrO 2 ⋅ 2H 2O, suggesting these compounds could be viable alternatives for industrial PEM electrolysers where durability is a key performance measure.

KW - amorphous iridium oxo-hydroxide

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Alkali Metal Iridates as Oxygen Evolution Catalysts Via Thermal Transformation of Amorphous Iridium (oxy)hydroxides.

Abstract

Data Availability Statement

Acknowledgements

Funding

Keywords

ASJC Scopus subject areas

UN SDGs

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