In this study, a novel sol−gel-derived Cu/TiO2 adsorbent has been demonstrated to exhibit exceptional capacities of 40.62, 49.52, and 108.48 mg PH3/g Cu/TiO2 for the oxidative capture of phosphine (PH3) in N2, air, and humidified air, respectively. We have proposed the oxidative mechanisms for PH3 on the Cu/TiO2 sample on the basis of elemental, chemical state, functional group, and microstructural analysis. Moreover, the influence of O2 and water vapor on the capture capacity is discussed. The transformation of PH3 followed the sequence of PH2 → H2P−OH → HP(OH)2 → P(OH)3 → HO−P═O → H3PO4. At the same time, the CuO/Cu(OH)2 moieties in the TiO2 lattice were reduced to Cu0. The H2P−OH and HO−P═O are the two stable intermediates, and they occupied the active species to inhibit further chemisorption. Direct oxidation of PH3 or the intermediates with adsorbed O2 was not efficient. However, the Cu/TiO2 sample catalyzed their interactions via reduction and then oxidation of the Cu2+ ions. Water vapor acts as a cocatalyst to facilitate the oxidation of the intermediates. The end product, H3PO4, migrated to bound the TiO2 support and free the CuO/Cu(OH)2 for the following catalytic processes. Although competitive adsorption of water molecules initially retarded the adsorption rate, the high extent of oxidation greatly promoted the capture capacity of the Cu/TiO2 in humidified air.The research was conducted at the NSRRC beamline 01C1 .
S. M. Chang, Y. Y. Hsu, and T. S. Chan