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Monitoring oxygen production on mass-selected iridium–tantalum oxide electrocatalysts

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Abstract

Development of low-cost and high-performance oxygen evolution reaction catalysts is key to implementing polymer electrolyte membrane water electrolysers for hydrogen production. Iridium-based oxides are the state-of-the-art acidic oxygen evolution reaction catalysts but still suffer from inadequate activity and stability, and iridium’s scarcity motivates the discovery of catalysts with lower iridium loadings. Here we report a mass-selected iridium–tantalum oxide catalyst prepared by a magnetron-based cluster source with considerably reduced noble-metal loadings beyond a commercial IrO2 catalyst. A sensitive electrochemistry/mass-spectrometry instrument coupled with isotope labelling was employed to investigate the oxygen production rate under dynamic operating conditions to account for the occurrence of side reactions and quantify the number of surface active sites. Iridium–tantalum oxide nanoparticles smaller than 2 nm exhibit a mass activity of 1.2 ± 0.5 kA gIr–1 and a turnover frequency of 2.3 ± 0.9 s−1 at 320 mV overpotential, which are two and four times higher than those of mass-selected IrO2, respectively. Density functional theory calculations reveal that special iridium coordinations and the lowered aqueous decomposition free energy might be responsible for the enhanced performance.

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Fig. 1: Preparation and characterization of mass-selected Ir–Ta NPs.
Fig. 2: Monitoring oxygen evolution on gold-supported mass-selected Ir0.1Ta0.9O2.45 NPs.
Fig. 3: Comparison of OER catalytic performance.
Fig. 4: Stability of mass-selected Ir0.1Ta0.9O2.45 NPs.
Fig. 5: Isotope labelling coupled with EC-MS-determined surface active sites and TOF values of mass-selected Ir0.1Ta0.9O2.45 NPs.
Fig. 6: Theoretical analysis of OER activity and stability.

Data availability

The authors declare that all data supporting the findings of this study are available within the paper and its Supplementary Information files and on DTU Data (https://doi.org/10.11583/DTU.16818703.v1). Source data are provided with this paper.

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Acknowledgements

Y.-R.Z. and Z.W acknowledge funding from the Toyota Research Institute. This project has received funding from VILLUM FONDEN (grant no. 9455) and the European Research Council under the European Union’s Horizon 2020 research and innovation programme (grants no. 741860-CLUNATRA, no. 815128−REALNANO and no. 770887−PICOMETRICS). S.B. and S.V.A. acknowledge funding from the Research Foundation Flanders (FWO, G026718N and G050218N). T.A. acknowledges the University of Antwerp Research Fund (BOF). STEM measurements were supported by the European Union’s Horizon 2020 Research Infrastructure-Integrating Activities for Advanced Communities under grant agreement no. 823717 – ESTEEM3.

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I.C., J.K. and J.K.N. conceived and supervised the project. Y.-R.Z. and Z.W co-wrote the manuscript. Y.-R.Z. performed electrochemical tests and collected and analysed the data. J.V., K.Z., T.-W.L., F.P. and N.M.S. performed the mass-selected NP preparation and XPS measurements. Z.W., A.C., M.A. and J.K.N. performed the DFT calculations. K.K., D.H. and S.B.S. assisted in the EC-MS data analysis. T.A., P.L. and S.B. performed the STEM experiments. J.F. and S.V.A. performed the quantitative analysis of the STEM data. C.M. performed the inductively coupled plasma MS measurements. All authors discussed the results and assisted during manuscript preparation.

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Correspondence to Jens K. Nørskov or Ib Chorkendorff.

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Zheng, YR., Vernieres, J., Wang, Z. et al. Monitoring oxygen production on mass-selected iridium–tantalum oxide electrocatalysts. Nat Energy 7, 55–64 (2022). https://doi.org/10.1038/s41560-021-00948-w

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