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1. Atomic level fluxional behavior and activity of CeO2-supported Pt catalysts for CO oxidation

   https://doi.org/10.1038/s41467-021-26047-8  

   Vincent, Joshua L.; Crozier, Peter A. (October 2021, Nature Communications)

   Abstract Reducible oxides are widely used catalyst supports that can increase oxidation reaction rates by transferring lattice oxygen at the metal-support interface. There are many outstanding questions regarding the atomic-scale dynamic meta-stability (i.e., fluxional behavior) of the interface during catalysis. Here, we employ aberration-correctedoperandoelectron microscopy to visualize the structural dynamics occurring at and near Pt/CeO₂interfaces during CO oxidation. We show that the catalytic turnover frequency correlates with fluxional behavior that (a) destabilizes the supported Pt particle, (b) marks an enhanced rate of oxygen vacancy creation and annihilation, and (c) leads to increased strain and reduction in the CeO₂support surface. Overall, the results implicate the interfacial Pt-O-Ce bonds anchoring the Pt to the support as being involved also in the catalytically-driven oxygen transfer process, and they suggest that oxygen reduction takes place on the highly reduced CeO₂surface before migrating to the interfacial perimeter for reaction with CO. 

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2. Modeling surface spin polarization on ceria-supported Pt nanoparticles

   https://doi.org/10.1088/1361-648X/ac62a3  

   Kang, Byungkyun; Vincent, Joshua L; Lee, Yongbin; Ke, Liqin; Crozier, Peter A; Zhu, Qiang (April 2022, Journal of Physics: Condensed Matter)

   Abstract In this work, we employ density functional theory simulations to investigate possible spin polarization of CeO 2 -(111) surface and its impact on the interactions between a ceria support and Pt nanoparticles. With a Gaussian type orbital basis, our simulations suggest that the CeO 2 -(111) surface exhibits a robust surface spin polarization due to the internal charge transfer between atomic Ce and O layers. In turn, it can lower the surface oxygen vacancy formation energy and enhance the oxide reducibility. We show that the inclusion of spin polarization can significantly reduce the major activation barrier in the proposed reaction pathway of CO oxidation on ceria-supported Pt nanoparticles. For metal-support interactions, surface spin polarization enhances the bonding between Pt nanoparticles and ceria surface oxygen, while CO adsorption on Pt nanoparticles weakens the interfacial interaction regardless of spin polarization. However, the stable surface spin polarization can only be found in the simulations based on the Gaussian type orbital basis. Given the potential importance in the design of future high-performance catalysts, our present study suggests a pressing need to examine the surface ferromagnetism of transition metal oxides in both experiment and theory. 

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3. α-MoC Supported Noble Metal Catalysts for Water–Gas Shift Reaction: Single-Atom Promoter or Single-Atom Player

   https://doi.org/10.1021/acs.jpclett.1c02762  

   Li, Juan; Sun, Li; Wan, Qiang; Lin, Jian; Lin, Sen; Wang, Xiaodong (November 2021, The Journal of Physical Chemistry Letters)

   In this work, we study the water−gas shift (WGS) reaction catalyzed by α- MoC(100) supported typical platinum group metal (PGM) single atoms (Rh1, Pd1, and Pt1) and Au1 via density functional theory calculations. The adsorption energies of key reaction intermediates and the kinetic barriers of the proposed rate-determining step in the WGS were systematically investigated. It is found that Rh1, Pd1, and Pt1 can serve as single-atom promoters (SAPs) to improve the WGS performance of surface Mo atoms on α-MoC(100). The enhanced activity originates from the fact that SAP modifies the electronic structure of Mo active sites. Comparatively, the Au1 species not only acts as an SAP but also directly participates in the catalysis as a single-atom player. The additional experiments with singleatomcatalyst performance and kinetic studies confirm the theoretical calculation conclusions. This study can provide a basis to further develop efficient WGS catalysts by tuning the activity of the substrate with intercalation of SAPs. 

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4. The effect of strong metal–support interaction (SMSI) on Pt–Ti/SiO ₂ and Pt–Nb/SiO ₂ catalysts for propane dehydrogenation

   https://doi.org/10.1039/d0cy00897d  

   Zhu Chen, Johnny; Gao, Junxian; Probus, Paige R.; Liu, Wei; Wu, Xianli; Wegener, Evan C.; Kropf, A. Jeremy; Zemlyanov, Dmitry; Zhang, Guanghui; Yang, Xin; et al (September 2020, Catalysis Science & Technology)

   null (Ed.)

   In this study, we show how strong metal–support interaction (SMSI) oxides in Pt–Nb/SiO 2 and Pt–Ti/SiO 2 affect the electronic, geometric and catalytic properties for propane dehydrogenation. Transmission electron microscopy (TEM), CO chemisorption, and decrease in the catalytic rates per gram Pt confirm that the Pt nanoparticles were partially covered by the SMSI oxides. X-ray absorption near edge structure (XANES), in situ X-ray photoelectron spectroscopy (XPS), and resonant inelastic X-ray scattering (RIXS) showed little change in the energy of Pt valence orbitals upon interaction with SMSI oxides. The catalytic activity per mol of Pt for ethylene hydrogenation and propane dehydrogenation was lower due to fewer exposed Pt sites, while turnover rates were similar. The SMSI oxides, however, significantly increase the propylene selectivity for the latter reaction compared to Pt/SiO 2 . In the SMSI catalysts, the higher olefin selectivity is suggested to be due to the smaller exposed Pt ensemble sites, which result in suppression of the alkane hydrogenolysis reaction; while the exposed atoms remain active for dehydrogenation. 

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5. Interpretable design of Ir-free trimetallic electrocatalysts for ammonia oxidation with graph neural networks

   https://doi.org/10.1038/s41467-023-36322-5  

   Pillai, Hemanth Somarajan; Li, Yi; Wang, Shih-Han; Omidvar, Noushin; Mu, Qingmin; Achenie, Luke E.; Abild-Pedersen, Frank; Yang, Juan; Wu, Gang; Xin, Hongliang (December 2023, Nature Communications)

   Abstract The electrochemical ammonia oxidation to dinitrogen as a means for energy and environmental applications is a key technology toward the realization of a sustainable nitrogen cycle. The state-of-the-art metal catalysts including Pt and its bimetallics with Ir show promising activity, albeit suffering from high overpotentials for appreciable current densities and the soaring price of precious metals. Herein, the immense design space of ternary Pt alloy nanostructures is explored by graph neural networks trained on ab initio data for concurrently predicting site reactivity, surface stability, and catalyst synthesizability descriptors. Among a few Ir-free candidates that emerge from the active learning workflow, Pt₃Ru-M (M: Fe, Co, or Ni) alloys were successfully synthesized and experimentally verified to be more active toward ammonia oxidation than Pt, Pt₃Ir, and Pt₃Ru. More importantly, feature attribution analyses using the machine-learned representation of site motifs provide fundamental insights into chemical bonding at metal surfaces and shed light on design strategies for high-performance catalytic systems beyond thed-band center metric of binding sites. 

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