Doped Tin Oxide Aerogels As Oxygen Evolution Reaction Catalyst Supports
Authors: Sola-Hernandez Lluis , Beauger Christian , Maillard Frédéric , Claudel Fabien 
Published: May 2020

Lowering the noble metal (Ir or Ru) loading of Oxygen Evolution Reaction (OER) catalysts while maintaining both a high activity and a long-term stability for Proton Exchange Membrane Water Electrolysis (PEMWE) cells is a challenging topic for industry and academia. A possible strategy is the use of support materials (Figure 1) that are stable under OER conditions (> 1.4 V vs. the standard hydrogen electrode).

Due to its large specific surface area and high electrical conductivity, carbon black is a popular and widely used catalyst support for electrochemical applications.[i] However its use is limited by the high anodic potentials required for the OER which would, due to corrosion, cause detachment of the supported catalyst.[ii] Therefore, non-carbon based supporting materials are required. Titanium dioxide (TiO2)[iii] or tin dioxide (SnO2)[iv] based materials are promising candidates due to their good corrosion resistance and strong interaction with noble metals catalysts. Wang and co-workers, reported enhanced OER activity and stability of antimony doped tin oxide (ATO)[v] aerogels supported Ir oxide nanoparticles.[vi] Uchida et al. also reported improved utilization of Ir deposited on tantalum doped tin oxide (TaTO) catalysts used at a PEMWE anode.[vii] However, Claudel et al. underlined that the stability of the doping element is a key issue for doped tin oxide to be implemented in PEMWE anodes.[viii]

In this work[ix], our 3D highly porous aerogel materials were revisited to prepare Sb or Ta-doped tin oxide based catalyst support. IrOx nanoparticles were in-situ deposited over the different doped tin oxide based aerogels. After synthesis and characterization of both the support and the IrOx nanoparticles, the OER activity was measured on glassy carbon rotating disk electrodes under conditions simulating PEMWE anode operation. Investigations were based on N2 sorption, Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD) and electrochemical characterization to analyse the physicochemical properties of the support and their impact on the catalytic activity and the stability of the catalysts.

Our results show that supported Ir oxide nanoparticles are both more active and more stable than unsupported ones. Consistently with the results reported by Uchida et al.,[vii] despite very different electronic conductivities of the supports, the OER mass activities of supported IrOx nanoparticles were found similar in thin-film electrode configuration.

Figure 1: Graphical representation of the designed anode for a PEWE cell, where the IrOx NPs are supported on a 3D porous aerogel material based on doped SnO2.

Acknowledgements

The authors wish to thank Pierre Ilbizian for supercritical drying, Frédéric Georgi for XPS analysis, Suzanne Jacomet for SEM/EDX analysis and Gabriel Monge for XRD analysis. This work was funded by the European Union's H2020 Program within the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement 779478 (FCH-JU project PRETZEL) and the French National Research Agency (ANR-17-CE05-0033 project MOISE). It was supported by Capenergies and Tenerrdis.

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Figure 1