Organophosphorus compounds have a wide range of reactivity depending on the coordination and oxidation state of the P atom. Due to their toxicity, certain organophosphonates are used as pesticides, herbicides, and, notoriously, as chemical nerve agents. The organophosphonate decomposition mechanism depends strongly on the substrate material, which motivates careful analysis of a range of potential materials for decontamination and sensing applications. Here, we present a study of the decomposition of dimethyl methylphosphonate (DMMP), a simulant molecule for the nerve agent sarin, on polycrystalline cuprous oxide surfaces (Cu2O). We use ambient pressure X-ray photoelectron spectroscopy (APXPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to monitor the pressure-dependent surface chemistry during exposure to DMMP vapor. At room temperature, we observe extensive degradation of DMMP, which includes the formation of reduced P products on the sample surface. We identify five unique P-containing species in the P 2p APXPS spectra, including atomic P and a surface-bound phosphinate [O=PH(OCH3)Osingle bondCu]. Here we propose a DMMP decomposition pathway whereby accumulation of this phosphinate species leads to an autocatalytic reaction on the Cu2O surface which yields reduced P species. After DMMP exposure, heating the Cu2O sample to 265°C leads to complete removal of all carbonaceous species and accumulation of a phosphate layer with stoichiometry similar to P2O5. These results introduce a new mechanism of room-temperature DMMP decomposition on metal oxides, which could be leveraged for the design of tailored metal oxide materials for catalyzing organophosphonate decomposition.
Trotochaud, Lena, Head, Ashley R., Büchner, Christin, et al., "Room temperature decomposition of dimethyl methylphosphonate on cuprous oxide yields atomic phosphorus," Surface Science 680, no. C (2018), https://doi.org/10.1016/j.susc.2018.10.003
@article{osti_1543597,
author = {Trotochaud, Lena and Head, Ashley R. and Büchner, Christin and Yu, Yi and Karslıoğlu, Osman and Tsyshevsky, Roman and Holdren, Scott and Eichhorn, Bryan and Kuklja, Maija M. and Bluhm, Hendrik},
title = {Room temperature decomposition of dimethyl methylphosphonate on cuprous oxide yields atomic phosphorus},
annote = {Organophosphorus compounds have a wide range of reactivity depending on the coordination and oxidation state of the P atom. Due to their toxicity, certain organophosphonates are used as pesticides, herbicides, and, notoriously, as chemical nerve agents. The organophosphonate decomposition mechanism depends strongly on the substrate material, which motivates careful analysis of a range of potential materials for decontamination and sensing applications. Here, we present a study of the decomposition of dimethyl methylphosphonate (DMMP), a simulant molecule for the nerve agent sarin, on polycrystalline cuprous oxide surfaces (Cu2O). We use ambient pressure X-ray photoelectron spectroscopy (APXPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to monitor the pressure-dependent surface chemistry during exposure to DMMP vapor. At room temperature, we observe extensive degradation of DMMP, which includes the formation of reduced P products on the sample surface. We identify five unique P-containing species in the P 2p APXPS spectra, including atomic P and a surface-bound phosphinate [O=PH(OCH3)Osingle bondCu]. Here we propose a DMMP decomposition pathway whereby accumulation of this phosphinate species leads to an autocatalytic reaction on the Cu2O surface which yields reduced P species. After DMMP exposure, heating the Cu2O sample to 265°C leads to complete removal of all carbonaceous species and accumulation of a phosphate layer with stoichiometry similar to P2O5. These results introduce a new mechanism of room-temperature DMMP decomposition on metal oxides, which could be leveraged for the design of tailored metal oxide materials for catalyzing organophosphonate decomposition.},
doi = {10.1016/j.susc.2018.10.003},
url = {https://www.osti.gov/biblio/1543597},
journal = {Surface Science},
issn = {ISSN 0039-6028},
number = {C},
volume = {680},
place = {United States},
publisher = {Elsevier},
year = {2018},
month = {10}}
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); University of Maryland, College Park, MD (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB); Defense Threat Reduction Agency (DTRA); National Science Foundation (NSF); Alexander von Humboldt Foundation; US Department of Education
Frank Ogletree, D.; Bluhm, Hendrik; Hebenstreit, Eleonore D.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 601, Issue 1-2https://doi.org/10.1016/j.nima.2008.12.155