Modeling atomically dispersed metals on oxides as catalysts for oxidative decomposition of chemical warfare agents
Abstract
Facile decomposition and neutralization of chemical warfare agents (CWAs) under ambient conditions is a major challenge in the modern world. Recent events demonstrate that there is an unmet need to better protect soldiers using personal protective ensembles that neutralize or destroy CWAs under ambient conditions. To achieve the goal of efficient CWA destruction under ambient conditions, new highly efficient catalysts are required. We propose to develop, from ab initio modeling, principles for designing new materials comprised of highly dispersed metal atoms, including single atoms, supported on metal oxides as catalysts for efficient oxidative decomposition of CWAs under ambient conditions. This proposed modeling has the potential for design of catalysts with high reactivity under moderate, ambient conditions by exploiting the high reactivity of open coordination sites on highly dispersed metal centers. The proposed research will address several key questions: ¥ What combination of metal oxides and metals yield stable highly dispersed metals centers in ambient conditions? What is the equilibrium oxidation state of theses highly dispersed metal centers? What are the underlying factors that determine stability? ¥ Which of these materials are computationally predicted to be most effective for oxidative decomposition of CWAs (sarin and mustard) and their simulants (Dimethyl methylphosphonate, DMMP and 2-Chloroethyl ethyl sulfide, CEES) and what is the mechanism and the kinetics for this decomposition, including the possible role of reactive peroxo species formed from O2? ¥ Can products be removed from the active site and stored on the oxide support? Or is there a threat that the active site is contaminated by the products? ¥ How do other gases in the environment, as water, affect the structure of the highly dispersed metal center and their efficiency for the catalytic oxidative decomposition? Density functional theory (DFT) calculations will be used to investigate the structure of highly dispersed metal sites, their oxidation state in ambient conditions, their stability against sintering and their reactivity for oxidation of CWAs (sarin and mustard) and their simulants (DMMP and CEES). The calculations will be performed with the VASP code Total energies will be combined with a thermodynamic treatment in order to assess the stability of various catalyst structures in reaction conditions. The exploration of geometric configuration will be performed manually for small catalytic species, but will use automated global optimization techniques for larger ones. Reaction pathways will be determined using a combination of nudged elastic band and dimer methods. DFT studies enable to rapidly screen for candidate materials that can then be tested experimentally. This approach will yield design principles for predicting stability and reactivity of catalysts. Simulants will be considered to facilitate the interaction with Virginia Tech. DFT will be used to also model actual CWAs to understand their reactivity, and to assess how well simulant used in academic experimental studies can predict CWA behavior. Experimental studies of CWAs on model materials will be performed in collaboration with researchers at Chemical and Biological Center (CBC) to further benchmark the theory. The longer-term goal of this work is to use the understanding gained from the modelling to design active and cost-effective catalysts for efficient CWA decomposition that can be incorporated into protective equipment.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 07, 2021
- Source ID
- W911NF2110361
Entities
People
- Philippe Sautet
Organizations
- Army Contracting Command
- United States Army
- University of California, Los Angeles