Mechanisms of Pd nanoparticle formation and strong metal-support interaction in Pd/TiO2 revealed by operando XAS

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Elizaveta KOZYR,

E. Kozyr¹, P. Paciok², R. Pellegrini³, M. Chiesa¹, Elena Groppo¹, L. Mino¹, A. Bugaev⁴

¹University of Turin, Italy; ²Forschungszentrum Jülich GmbH, Germany; ³ALBAChimet S.p.A, Italy;
⁴Paul Scherrer Institute, Switzerland; elizaveta.kozyr@unito.it

Understanding the formation of active phases and metal-support interactions is essential for the rational design of efficient photocatalysts. In this work, Pd/TiO₂ catalysts prepared by photodeposition and deposition-precipitation were investigated using a combination of operando synchrotron-based X-ray absorption spectroscopy (XAS) and complementary microscopic and spectroscopic techniques. A custom operando photocatalytic cell enabled in situ monitoring of the Pd photodeposition process, revealing the formation of single-atom Pd(0) sites as an initial step followed by the growth of ~1 nm Pd nanoparticles with narrow size distribution. Photodeposited catalysts exhibit strong metal-support interaction (SMSI), associated with the presence of Ti³⁺ sites at the Pd/TiO₂ interface and direct Pd-Ti interactions observed by XAS, EPR, and EELS. These features lead to enhanced stabilization of metallic Pd even under oxidizing conditions, in contrast to catalysts prepared by deposition-precipitation. The results highlight how synthesis pathways govern nanoparticle formation mechanisms and metal-support interactions in Pd/TiO₂ photocatalysts.

Acknowledgements

We thank ReMade@ARIE funded by the European Union as part of the Horizon Europe call HORIZON-INFRA-2021-SERV-01 under grant agreement number 101058414 and co-funded by the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number 22.00187 for the access to the HR-STEM measurements (ERC, Julich, Germany) and XAS measurements at SuperXAS beamline of Swiss Light Source.