More Like this

1. Enantiospecific equilibrium adsorption and chemistry of d ‐/ l ‐proline mixtures on chiral and achiral Cu surfaces

   https://doi.org/10.1002/chir.23153  

   Dutta, Soham; Gellman, Andrew J. (November 2019, Chirality)

   Abstract A fundamental understanding of the enantiospecific interactions between chiral adsorbates and understanding of their interactions with chiral surfaces is key to unlocking the origins of enantiospecific surface chemistry. Herein, the adsorption and decomposition of the amino acid proline (Pro) have been studied on the achiral Cu(110) and Cu(111) surfaces and on the chiral Cu(643)^R&Ssurfaces. Isotopically labelled 1‐¹³C‐l‐Pro has been used to probe the Pro decomposition mechanism and to allow mass spectrometric discrimination ofd‐Pro and 1‐¹³C‐l‐Pro when adsorbed as mixtures. On the Cu(111) surface, X‐ray photoelectron spectroscopy reveals that Pro adsorbs as an anionic species in the monolayer. On the chiral Cu(643)^R&Ssurface, adsorbed Pro enantiomers decompose with non‐enantiospecific kinetics. However, the decomposition kinetics were found to be different on the terraces versus the kinked steps. Exposure of the chiral Cu(643)^R&Ssurfaces to a racemic gas phase mixture ofd‐Pro and 1‐¹³C‐l‐Pro resulted in the adsorption of a racemic mixture; i.e., adsorption is not enantiospecific. However, exposure to non‐racemic mixtures ofd‐Pro and 1‐¹³C‐l‐Pro resulted in amplification of enantiomeric excess on the surface, indicative of homochiral aggregation of adsorbed Pro. During co‐adsorption, this amplification is observed even at very low coverages, quite distinct from the behavior of other amino acids, which begin to exhibit homochiral aggregation only after reaching monolayer coverages. The equilibrium adsorption ofd‐Pro and 1‐¹³C‐l‐Pro mixtures on achiral Cu(110) did not display any aggregation, consistent with prior scanning tunneling microscopy (STM) observations ofdl‐Pro/Cu(110). This demonstrates convergence between findings from equilibrium adsorption methods and STM experiments and corroborates formation of a 2D random solid solution. 

   more » « less
2. Reaction pathways for HCN on transition metal surfaces

   https://doi.org/10.1039/C8CP07548D  

   Abdel-Rahman, Mohammed; Feng, Xu; Muir, Mark; Ghale, Kushal; Xu, Ye; Trenary, Michael (February 2019, Physical Chemistry Chemical Physics)

   The adsorption and decomposition of HCN on the Pd(111) and Ru(001) surfaces have been studied with reflection absorption infrared spectroscopy and density functional theory calculations. The results are compared to earlier studies of HCN adsorption on the Pt(111) and Cu(100) surfaces. In all cases the initial adsorption at low temperatures gives rise to a ν (C–H) stretch peak at ∼3300 cm −1 , which is very close to the gas phase value indicating that the triple CN bond is retained for the adsorbed molecule. When the Pd(111) surface is heated to room temperature, the HCN is converted to the aminocarbyne species, CNH 2 , which was also observed on the Pt(111) surface. DFT calculations confirm the high stability of CNH 2 on Pd(111), and suggest a bi-molecular mechanism for its formation. When HCN on Cu(100) is heated, it desorbs without reaction. In contrast, no stable intermediates are detected on Ru(001) as the surface is heated, indicating that HCN decomposes completely to atomic species. 

   more » « less
3. Structure Sensitivity and Catalyst Restructuring for CO2 Electro-reduction on Copper

   https://doi.org/10.1038/s41467-025-59267-3  

   Cheng, Dongfang; Nguyen, Khanh-Ly_C; Sumaria, Vaidish; Wei, Ziyang; Zhang, Zisheng; Gee, Winston; Li, Yichen; Morales-Guio, Carlos_G; Heyde, Markus; Roldan_Cuenya, Beatriz; et al (April 2025, Nature Communications)

   Abstract Cu is the most promising metal catalyst for CO₂electroreduction (CO₂RR) to multi-carbon products, yet the structure sensitivity of the reaction and the stability versus restructuring of the catalyst surface under reaction conditions remain controversial. Here, atomic scale simulations of surface energies and reaction pathway kinetics supported by experimental evidence unveil that CO₂RR does not take place on perfect planar Cu(111) and Cu(100) surfaces but rather on steps or kinks. These planar surfaces tend to restructure in reaction conditions to the active stepped surfaces, with the strong binding of CO on defective sites acting as a thermodynamic driving force. Notably, we identify that the square motifs adjacent to defects, not the defects themselves, as the active sites for CO₂RR via synergistic effect. We evaluate these mechanisms against experiments of CO₂RR on ultra-high vacuum-prepared ultraclean Cu surfaces, uncovering the crucial role of step-edge orientation in steering selectivity. Overall, our study refines the structural sensitivity of CO₂RR on Cu at the atomic level, highlights the self-activation mechanism and elucidates the origin of in situ restructuring of Cu surfaces during the reaction. 

   more » « less
4. Crotonaldehyde Adsorption on Cu-Pt Surface Alloys: A Quantum Mechanics Study

   https://doi.org/10.3390/chemistry5010034  

   Ruvalcaba, Ricardo; Guerrero-Sanchez, Jonathan; Takeuchi, Noboru; Zaera, Francisco (March 2023, Chemistry)

   The adsorption of crotonaldehyde on Cu-Pt alloy surfaces was characterized by density functional theory (DFT). Two surfaces were considered: Cu2Pt/Cu(111) and Cu3Pt/Cu(111). It was determined that the presence of Pt on the surface, even when isolated as single atoms fully surrounded by Cu, provides additional stability for the adsorbates, increasing the magnitude of the adsorption energy by as much as 40 kJ/mol. The preferred bonding on both surfaces is via multiple coordination, with the most stable configuration being a cis arrangement with di-σ bonding of the C=O bond across a Cu–Cu bridge and an additional π bonding to a Pt atom. The fact that Pt significantly affects the adsorption of unsaturated aldehydes such as crotonaldehyde explains why the kinetics of their hydrogenation using single-atom alloy (SAA) catalysts vary with alloy composition, as we previously reported, and brings into question the simple model in which the role of Pt is only to promote the dissociation of H2. 

   more » « less
5. Templated Growth of a Homochiral Thin Film Oxide

   https://doi.org/10.1021/acsnano.0c00398  

   Schilling, Alex C.; Therrien, Andrew J.; Hannagan, Ryan T.; Marcinkowski, Matthew D.; Kress, Paul L.; Patel, Dipna A.; Balema, Tedros A.; Larson, Amanda M.; Lucci, Felicia R.; Coughlin, Benjamin P.; et al (April 2020, ACS Nano)

   Chiral surfaces are of growing interest for enantioselective adsorption and reactions. While metal surfaces can be prepared with a wide range of chiral surface orientations, chiral oxide surface preparation is much more challenging. Herein, we demonstrate that the chirality of a metal surface can be used to direct the homochiral growth of a thin film chiral oxide. Specifically, we study the chiral ‘29’ copper oxide, formed by oxidizing a Cu(111) single crystal at 650 K. Surface structure spread single crystals which expose a continuous distribution of surface orientations as a function of position on the crystal, enabled us to systematically investigate the mechanism of chirality transfer between metal and oxide with high-resolution scanning tunneling microscopy. We discovered that the local underlying metal facet directs the orientation and chirality of the oxide overlayer. Importantly, single homochiral domains of the ‘29’ oxide were found in areas where the Cu step edges that templated growth were ≤20 nm apart. We used this information to select a Cu(239 241 246) oriented single crystal and demonstrate that a ‘29’ oxide surface can be grown in homochiral domains by templating from the subtle chirality of the underlying metal crystal. This work demonstrates how a small degree of chirality induced by very slight misorientation of a metal surface (~1 sites/ 20 nm2) can be amplified by oxidation to yield a homochiral oxide with a regular array of chiral oxide pores (~75 sites/ 20 nm2). This offers a general approach for making chiral oxide surfaces via oxidation of an appropriately miscut metal surface. 

   more » « less