Adsorption and Decomposition of Dimethyl Methylphosphonate on ZnO And TiO2
The accelerated decomposition of organophosphorus compounds on semiconductor oxide surfaces is being investigated as a method of destroying pesticide pollutants. Fourier transform infrared (FTIR) spectroscopy was used to monitor the gas-solid thermal and photochemical decomposition of dimethylmethylphosphonate (DMMP) on ZnO and Ti02 powder. DMMP adsorbs onto the semiconductor surface through the P=0 bond as indicated by a 20 cm−1 shift to lower frequency for the P=0 stretch. The other vibrations of the adsorbed DMMP changed by less than 4 cm−1. The intermediate is stable indefinitely on ZnO at room temperature and cannot be removed by pumping. The DMMP is less strongly bound on TiO2 and at ambient temperature either desorbs or rearranges to the bridged structure (vide infra).