Towards stable and highly active IrO2 catalysts supported on doped tin oxides for the oxygen evolution reaction in acidic media

Sofia Delgado,Eva Sousa,K.A Friedrich,Paranjeet Lakhtaria,Adélio Mendes,Tiago Lagarteira,V Cigolotti

doi:10.1051/e3sconf/202233403001

Sofia Delgado, Eva Sousa + Show 5 more

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https://doi.org/10.1051/e3sconf/202233403001

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Abstract

Iridium oxide is the preferred catalyst for water oxidation but it is required to maximize its utilization to deploy Proton Exchange Membrane Water Electrolyzers (PEMWEs) into the large-scale applications panorama. A promising pathway for dispersing this precious catalyst is on an electric conductive and stable support. However, there is a lack of understanding how the support-catalyst interactions affect the stability/activity of the electrocatalyst under anodic conditions. This work discloses a modified, easy-scalable, polyol synthesis protocol to produce a highly active and stable iridium-based catalyst, supported on metal-doped tin oxides. The loading of Ir was reduced 30 wt.% compared to the reference IrO2, and dispersed on Sb-SnO2 (IrOx/ATO), In-SnO2 (IrOx/ITO) and SnO2 supports. All synthesized electrocatalysts not only surpassed the OER-mass activity of a commercial catalyst (IrO2) – reference – but also reached higher electrochemical active surface areas and enhanced stability under the OER conditions. The highest performance was achieved with Ir NPs supported on ITO (176 A/gIr vs. 15.5 A/gIr for the reference catalyst @ 1.51 V vs. RHE) and both IrOx/ITO and IrOx/SnO2 catalysts demonstrated remarkable stability after cycling the electrode and performing long-term chronopotentiometry. ITO is, therefore, an auspicious support to serve Ir-based catalysts as it favors a good bargain between activity and stability, while drastically reducing the amount of noble metal.

Highlights

Proton exchange membrane water electrolyzers (PEMWEs) exhibit excellent features for the production of green hydrogen, by mitigating the intermittency and fluctuation of renewable energy sources, and allowing the decarbonization of the electrical grids[1]
From ca. 850 °C to 1000 °C, iridium tends to degrade from IrO2 to IrO and the fact that Ir is dispersed on a tin oxide support enables to increase the thermal stability as the weight drop is less significant for all the prepared electrocatalysts comparatively, to non-supported commercial IrO2 [12]
A modified polyol chemical reduction synthesis route was effectively utilized to produce highly active and stable electrocatalysts consisting of 30 wt. % of noble Ir metal dispersed on ATO, ITO and SnO2 nanoparticles

Summary

Introduction

Proton exchange membrane water electrolyzers (PEMWEs) exhibit excellent features for the production of green hydrogen, by mitigating the intermittency and fluctuation of renewable energy sources, and allowing the decarbonization of the electrical grids[1]. For lowering the loading of such PGMs, the development of highly-structured catalysts that utilize PGM more effectively, the catalyst must display high mass activities, while being durable and possessing low volumetric packing density [5] Overcoming these challenges will push PEM electrolysis into an economically feasible panorama to serve the large-scale production of green hydrogen. By dispersing Ir catalysts onto high electrical conductive, large surface area (m2/g) and highly corrosion resistant supports, there is a possibility to reduce the Ir-loading, while ensuring the maximum utilization of the noble metal to increase the OER mass activity [6] These approaches are required to achieve the target for the reduction of today’s Ir-specific power density in ca. These approaches are required to achieve the target for the reduction of today’s Ir-specific power density in ca. 50-fold, down to ca. 0.01 gIr/kW while maintaining high efficiency (assuming electrolyzer efficiency of 70 % LHV – cell potential of ca.1.79 V ) [7]

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