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Modulating electronic properties of trimetallic sites on defective ceria for efficient CO 2 conversion Charvi Singhvi 1 , Gunjan Sharma 1 , Rishi Verma 1 , Vinod K. Paidi 2 , Pieter Glatzel 2 , Paul Paciok 3 , Vashishtha B. Patel 4 , Ojus Mohan, 4 Vivek Polshettiwar *1 1 Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai, India. 2 European Synchrotron Radiation Facility, Grenoble, France. 3 Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India. 4 Ernst-Ruska Center for Microscopy and Spectroscopy with Electrons, Jülich, Germany. E-mail: charvi.singhvi@tifr.res.in, vivek.pol@tifr.res.in Despite the advancements made in the domain of heterogeneous catalysis, the development of optimal catalysts is hampered by challenges such as moderate catalytic activity, poor stability, coking, and loss of selectivity at high reaction temperatures, which made the processes unsustainable. SMSI, as reported by Tauster et al. 1 enables strong anchoring of metal active sites on the support inhibiting deactivation of the catalyst via sintering. The phenomenon also offers a distinct advantage in orchestrating electron shuffling between metallic sites and oxide support at the metal nanoparticle and support interface, leading to unique electron density distribution at the active sites. 2,3 It facilitates the creation of abundant electron-rich or deficient interfacial active sites, thereby exerting significant influence on the adsorption behaviour of reactant molecules and intermediate species, consequently tuning on catalytic activity and selectivity by catalysing the reaction through targeted reaction pathways. We designed and synthesised a Ni-Cu-Zn/CeO 2 catalyst featuring a unique electron density distribution, achieved through the strategic integration of defects and SMSI. This catalyst demonstrated a CO productivity of 49,279 mmol g -1 h -1 (equivalent to 10,484,894 mmol gmetal -1 h -1 ) at 650 °C—a nine-fold improvement over the best-reported catalysts. 4 It also delivered CO selectivity of up to 99%, with activity remaining unchanged even after 100 hours on stream at 500 °C. This raises an intriguing question: with conventional ceria and typical metal sites, what makes this combination of trimetallic Ni-Cu-Zn sites and defective ceria support so exceptional? The catalyst’s extraordinary activity and stability arise from the synergistic interplay among the Ni-Cu-Zn sites and their SMSI with the defective ceria support. Insights from in-situ TEM, STEM-EELS, and HERFD-XANES studies revealed the dynamic interactions and the distinctive electron density distribution between the CeO 2 support, its defects, and the trimetallic nanoparticles. These studies highlighted the critical role of ceria oxygen vacancies in both CO2 activation and coke suppression during catalysis. In-situ TEM imaging under catalytic conditions captured the movement and growth of active trimetallic sites, showing that their diffusion and sintering ceased once SMSI was established, even at elevated temperatures. These insights provide a unique perspective on catalyst design, defect engineering and SMSI in achieving unparalleled catalytic performance. Key words: SMSI, trimetallic nanoparticles, defects, in-situ TEM, in-situ XAS References 1. S. J. Tauster, S. C. Fung, R. M. Baker, J. A. Horsley, Science 211 , 1121– 1125 (1981). 2. R. Belgamwar, R. Verma, T. Das, S. Chakraborty, P. B. Sarawade, V. Polshettiwar, J. Am. Chem. Soc. 145, 8634–8646 (2023). 3. A. K. Mishra, R. Belgamwar, R. Jana, A. Datta, V. Polshettiwar, P roc. Natl. Acad. Sci. U. S. A. 117 , 6383–6390 (2020). 4. C. Singhvi, G. Sharma, R. Verma, et al. Proc. Natl. Acad. Sci. U. S. A. 122 , e2411406122 (2025).
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