Adsorption and Photo-Degradation of Organophosphates on Sulfate-Terminated Anatase TiO2 Nanoparticles

The adsorption and photocatalytic degradation of trimethyl phosphate (TMP) triethyl (TEP), two environmentally relevant model pollutants, have been studied on commercial anatase TiO2 sulfate-terminated nanoparticles by means operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy 2D correlation (2D COS). It is concluded that both TMP TEP adsorb dissociatively TiO2, while the associatively. Upon UV illumination, are completely oxidized as evidenced evolution IR bands characteristic for water carbon dioxide. In contrast, illumination leads to formation stable surface-coordinated carboxylate products, which impedes complete oxidation. COS analysis suggests parallel reaction pathways occur during oxidation under viz. methoxide/ethoxide (ads) → carboxylates aldehydes (ads). A occurs sulfated yields CO2 H2O direct radical reactions with methoxide groups little, or no, intermediates. Sulfated favor aldehyde intermediates, rates 10 times 30 faster TEM, respectively, compared TiO2. About 37% (33%) 32% (24%) (TEP) were degraded sulfated-terminated pure after first 9 min illumination. We show sulfate-functionalization has main functions. First, it prevents strongly bonded bridging carboxylates, thereby alleviating deactivation. Second, promotes full organic side-chains into dioxide water. Improved electron-hole separation electrophilic S(VI) in combination blocking intermediates proposed contribute improved activity. presented results give insights how acidic surface modifications change adsorbate chemistries, can be used increase sustained activity low-temperature photocatalysts.