Baraa Werghi

All Publications

• Selective Catalytic Behavior Induced by Crystal-Phase Transformation in Well-Defined Bimetallic Pt-Sn Nanocrystals. Small (Weinheim an der Bergstrasse, Germany) Werghi, B., Wu, L., Ebrahim, A. M., Chi, M., Ni, H., Cargnello, M., Bare, S. R. 2023: e2207956

  Abstract

  The Pt-Sn bimetallic system is a much studied and commercially used catalyst for propane dehydrogenation. The traditionally prepared catalyst, however, suffers from inhomogeneity and phase separation of the active Pt-Sn phase. Colloidal chemistry offers a route for the synthesis of Pt-Sn bimetallic nanoparticles (NPs) in a systematic, well-defined, tailored fashion over conventional methods. Here, the successful synthesis of well-defined ≈2 nm Pt, PtSn, and Pt3 Sn nanocrystals with distinct crystallographic phases is reported; hexagonal close packing (hcp) PtSn and fcc Pt3 Sn show different activity and stability depending on the hydrogen-rich or poor environment in the feed. Moreover, face centred cubic (fcc) Pt3 Sn/Al2 O3 , which exhibited the highest stability compared to hcp PtSn, shows a unique phase transformation from an fcc phase to an L12 -ordered superlattice. Contrary to PtSn, H2 cofeeding has no effect on the Pt3 Sn deactivation rate. The results reveal structural dependency of the probe reaction, propane dehydrogenation, and provide a fundamental understanding of the structure-performance relationship on emerging bimetallic systems.

  View details for DOI 10.1002/smll.202207956

  View details for PubMedID 36807838

• Formic Acid Dehydrogenation via an Active Ruthenium Pincer Catalyst Immobilized on Tetra-Coordinated Aluminum Hydride Species Supported on Fibrous Silica Nanospheres ACS CATALYSIS Yaacoub, L., Dutta, I., Werghi, B., Chen, B. J., Zhang, J., Abou Hamad, E., Ang, E., Pump, E., Sedjerari, A., Huang, K., Basset, J. 2022: 14408-14417

  View details for DOI 10.1021/acscatal.2c04137

  View details for Web of Science ID 000884444100001

• Steering CO2 hydrogenation toward C-C coupling to hydrocarbons using porous organic polymer/metal interfaces. Proceedings of the National Academy of Sciences of the United States of America Zhou, C., Asundi, A. S., Goodman, E. D., Hong, J., Werghi, B., Hoffman, A. S., Nathan, S. S., Bent, S. F., Bare, S. R., Cargnello, M. 2022; 119 (7)

  Abstract

  The conversion of CO2 into fuels and chemicals is an attractive option for mitigating CO2 emissions. Controlling the selectivity of this process is beneficial to produce desirable liquid fuels, but C-C coupling is a limiting step in the reaction that requires high pressures. Here, we propose a strategy to favor C-C coupling on a supported Ru/TiO2 catalyst by encapsulating it within the polymer layers of an imine-based porous organic polymer that controls its selectivity. Such polymer confinement modifies the CO2 hydrogenation behavior of the Ru surface, significantly enhancing the C2+ production turnover frequency by 10-fold. We demonstrate that the polymer layers affect the adsorption of reactants and intermediates while being stable under the demanding reaction conditions. Our findings highlight the promising opportunity of using polymer/metal interfaces for the rational engineering of active sites and as a general tool for controlling selective transformations in supported catalyst systems.

  View details for DOI 10.1073/pnas.2114768119

  View details for PubMedID 35135880

• Colloidal Platinum-Copper Nanocrystal Alloy Catalysts Surpass Platinum in Low-Temperature Propene Combustion. Journal of the American Chemical Society Tahsini, N., Yang, A. C., Streibel, V., Werghi, B., Goodman, E. D., Aitbekova, A., Bare, S. R., Li, Y., Abild-Pedersen, F., Cargnello, M. 2022

  Abstract

  Low-temperature removal of noxious environmental emissions plays a critical role in minimizing the harmful effects of hydrocarbon fuels. Emission-control catalysts typically consist of large quantities of rare, noble metals (e.g., platinum and palladium), which are expensive and environmentally damaging metals to extract. Alloying with cheaper base metals offers the potential to boost catalytic activity while optimizing the use of noble metals. In this work, we show that PtxCu100-x catalysts prepared from colloidal nanocrystals are more active than the corresponding Pt catalysts for complete propene oxidation. By carefully controlling their composition while maintaining nanocrystal size, alloys with dilute Cu concentrations (15-30% atomic fraction) demonstrate promoted activity compared to pure Pt. Complete propene oxidation was observed at temperatures as low as 150 °C in the presence of steam, and five to ten times higher turnover frequencies were found compared to monometallic Pt catalysts. Through DFT studies and structural and catalytic characterization, the remarkable activity of dilute PtxCu100-x alloys was related to the tuning of the electronic structure of Pt to reach optimal binding energies of C* and O* intermediates. This work provides a general approach toward investigation of structure-property relationships of alloyed catalysts with efficient and optimized use of noble metals.

  View details for DOI 10.1021/jacs.1c10248

  View details for PubMedID 35050603

• Insights and comparison of structure-property relationships in propane and propene catalytic combustion on Pd- and Pt-based catalysts JOURNAL OF CATALYSIS Yang, A., Streibel, V., Choksi, T. S., Aljama, H., Werghi, B., Bare, S. R., Sanchez-Carrera, R. S., Schaefer, A., Li, Y., Abild-Pedersen, F., Cargnello, M. 2021; 401: 89-101

  View details for DOI 10.1016/j.jcat.2021.06.018

  View details for Web of Science ID 000691545800010