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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. 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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3. 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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4. Emergence of exchange bias in van der Waals magnetic alloy CrxPt1−xTe2

   https://doi.org/10.1038/s44306-024-00028-1  

   Bailey-Crandell, Ryan; Huey, Warren_L B; Williams, Archibald J; Zhou, Wenyi; Goldberger, Joshua E; Kawakami, Roland K (December 2024, npj Spintronics)

   Abstract Cr_xPt_1−xTe₂is a recently developed van der Waals magnetic alloy noted for its stability under ambient conditions. Here, we report the emergence of an exchange bias effect in Cr_xPt_1−xTe₂, without typical exchange bias sources such as an adjacent antiferromagnetic layer. We find that the exchange bias is present forx = 0.45 and absent forx = 0.35, which is correlated to the presence of a Cr modulation where the Cr concentration alternates each vdW layer (modulation period of 2 layers) forx ≥ 0.4. We perform Monte Carlo simulations utilizing exchange parameters from first-principles calculations, which recreate the exchange bias in hysteresis loops of Cr_0.45Pt_0.55Te₂. From our simulations, we infer the source of exchange bias to be magnetic moments locked into free energy minima that resist magnetization reversal. This work presents a way to introduce desirable magnetic properties to van der Waals magnets. 

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5. 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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