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1. 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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2. New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na ₂ WO ₄ /SiO ₂ Catalysts

   https://doi.org/10.1002/anie.202108201  

   Sourav, Sagar; Wang, Yixiao; Kiani, Daniyal; Baltrusaitis, Jonas; Fushimi, Rebecca_R; Wachs, Israel_E (August 2021, Angewandte Chemie International Edition)

   Abstract The complex structure of the catalytic active phase, and surface‐gas reaction networks have hindered understanding of the oxidative coupling of methane (OCM) reaction mechanism by supported Na₂WO₄/SiO₂catalysts. The present study demonstrates, with the aid of in situ Raman spectroscopy and chemical probe (H₂‐TPR, TAP and steady‐state kinetics) experiments, that the long speculated crystalline Na₂WO₄active phase is unstable and melts under OCM reaction conditions, partially transforming to thermally stable surface Na‐WO_xsites. Kinetic analysis via temporal analysis of products (TAP) and steady‐state OCM reaction studies demonstrate that (i) surface Na‐WO_xsites are responsible for selectively activating CH₄to C₂H_xand over‐oxidizing CH_yto CO and (ii) molten Na₂WO₄phase is mainly responsible for over‐oxidation of CH₄to CO₂and also assists in oxidative dehydrogenation of C₂H₆to C₂H₄. These new insights reveal the nature of catalytic active sites and resolve the OCM reaction mechanism over supported Na₂WO₄/SiO₂catalysts. 

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3. Selectivity for ethanol partial oxidation: the unique chemistry of single-atom alloy catalysts on Au, Ag, and Cu(111)

   https://doi.org/10.1039/C9TA04572D  

   Li, Hao; Chai, Wenrui; Henkelman, Graeme (October 2019, Journal of Materials Chemistry A)

   Recently, we found that the atomic ensemble effect is the dominant effect influencing catalysis on surfaces alloyed with strong- and weak-binding elements, determining the activity and selectivity of many reactions on the alloy surface. In this study we design single-atom alloys that possess unique dehydrogenation selectivity towards ethanol (EtOH) partial oxidation, using knowledge of the alloying effects from density functional theory calculations. We found that doping of a strong-binding single-atom element ( e.g. , Ir, Pd, Pt, and Rh) into weak-binding inert close-packed substrates ( e.g. , Au, Ag, and Cu) leads to a highly active and selective initial dehydrogenation at the α-C–H site of adsorbed EtOH. We show that many of these stable single-atom alloy surfaces not only have tunable hydrogen binding, which allows for facile hydrogen desorption, but are also resistant to carbon coking. More importantly, we show that a rational design of the ensemble geometry can tune the selectivity of a catalytic reaction. 

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4. Facet-selective deposition of Au and Pt on Ag nanocubes for the fabrication of bifunctional Ag@Au–Pt nanocubes and trimetallic nanoboxes

   https://doi.org/10.1039/c8nr01794h  

   Zhang, Zhiwei; Ahn, Jaewan; Kim, Junki; Wu, Zhengyun; Qin, Dong (January 2018, Nanoscale)

   We report a facile route to the synthesis of Ag@Au–Pt trimetallic nanocubes in which the Ag, Au, and Pt atoms are exposed at the corners, side faces, and edges, respectively. Our success relies on the use of Ag@Au nanocubes, with Ag 2 O patches at the corners and Au on the side faces and edges, as seeds for the site-selective deposition of Pt on the edges only in a reaction system containing ascorbic acid (H 2 Asc) and poly(vinylpyrrolidone). At an initial pH of 3.2, H 2 Asc can dissolve the Ag 2 O patches, exposing the Ag atoms at the corners of a nanocube. Upon the injection of the H 2 PtCl 6 precursor, the Pt atoms derived from the reduction by both H 2 Asc and Ag are preferentially deposited on the edges, leading to the formation of Ag@Au–Pt trimetallic nanocubes. We demonstrate the use of 2,6-dimethylphenyl isocyanide as a molecular probe to confirm and monitor the deposition of Pt atoms on the edges of nanocubes through surface-enhanced Raman scattering (SERS). We further explore the use of these bifunctional trimetallic nanoparticles with integrated plasmonic and catalytic properties for in situ SERS monitoring the reduction of 4-nitrothiophenol by NaBH 4 . Upon the removal of Ag via H 2 O 2 etching, the Ag@Au–Pt nanocubes evolve into trimetallic nanoboxes with a wall thickness of about 2 nm and well-defined openings at the corners. The trimetallic nanoboxes embrace plasmon resonance peaks in the near-infrared region with potential in biomedical applications. 

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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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