All Publications

  • Effect of Fluoroalkylsilane Surface Functionalization on Boron Combustion. ACS applied materials & interfaces Baek, J., Jiang, Y., Demko, A. R., Jimenez-Thomas, A. R., Vallez, L., Ka, D., Xia, Y., Zheng, X. 2022


    Boron has been regarded as a promising high-energy fuel due to its high volumetric and gravimetric heating values. However, it remains challenging for boron to attain its theoretical heat of combustion because of the existence of its native boron oxide layer and its high melting and boiling temperatures that delay ignition and inhibit complete combustion. Boron combustion is known to be enhanced by physically adding fluorine-containing chemicals, such as fluoropolymer or metal fluorides, to remove surface boron oxides. Herein, we chemically functionalize the surface of boron particles with three different fluoroalkylsilanes: FPTS-B (F3-B), FOTS-B (F13-B), and FDTS-B (F17-B). We evaluated the ignition and combustion properties of those three functionalized boron particles as well as pristine ones. The boron particles functionalized with the longest fluorocarbon chain (F17) exhibit the most powerful energetic performance, the highest heat of combustion, and the strongest BO2 emission among all samples. These results suggest that the surface functionalization with fluoroalkylsilanes is an efficient strategy to enhance boron ignition and combustion.

    View details for DOI 10.1021/acsami.2c00347

    View details for PubMedID 35467848

  • Enhancing Electrochemical Water Oxidation toward H2O2 via Carbonaceous Electrolyte Engineering ACS APPLIED ENERGY MATERIALS Gill, T., Vallez, L., Zheng, X. 2021; 4 (11): 12429-12435
  • The Role of Bicarbonate-Based Electrolytes in H2O2 Production through Two-Electron Water Oxidation ACS ENERGY LETTERS Gill, T., Vallez, L., Zheng, X. 2021; 6 (8): 2854-2862
  • Operando Study of Thermal Oxidation of Monolayer MoS2 ADVANCED SCIENCE Park, S., Garcia-Esparza, A. T., Abroshan, H., Abraham, B., Vinson, J., Gallo, A., Nordlund, D., Park, J., Kim, T., Vallez, L., Alonso-Mori, R., Sokaras, D., Zheng, X. 2021
  • Effect of Adventitious Carbon on Pit Formation of Monolayer MoS2. Advanced materials (Deerfield Beach, Fla.) Park, S., Siahrostami, S., Park, J., Mostaghimi, A. H., Kim, T. R., Vallez, L., Gill, T. M., Park, W., Goodson, K. E., Sinclair, R., Zheng, X. 2020: e2003020


    Forming pits on molybdenum disulfide (MoS2 ) monolayers is desirable for (opto)electrical, catalytic, and biological applications. Thermal oxidation is a potentially scalable method to generate pits on monolayer MoS2 , and pits are assumed to preferentially form around undercoordinated sites, such as sulfur vacancies. However, studies on thermal oxidation of MoS2 monolayers have not considered the effect of adventitious carbon (C) that is ubiquitous and interacts with oxygen at elevated temperatures. Herein, the effect of adventitious C on the pit formation on MoS2 monolayers during thermal oxidation is studied. The in situ environmental transmission electron microscopy measurements herein show that pit formation is preferentially initiated at the interface between adventitious C nanoparticles and MoS2 , rather than only sulfur vacancies. Density functional theory (DFT) calculations reveal that the C/MoS2 interface favors the sequential adsorption of oxygen atoms with facile kinetics. These results illustrate the important role of adventitious C on pit formation on monolayer MoS2 .

    View details for DOI 10.1002/adma.202003020

    View details for PubMedID 32743836

  • ZnO As an Active and Selective Catalyst for Electrochemical Water Oxidation to Hydrogen Peroxide ACS CATALYSIS Kelly, S. R., Shi, X., Back, S., Vallez, L., Park, S., Siahrostami, S., Zheng, X., Norskov, J. K. 2019; 9 (5): 4593–99