Surface Chemistry of 2-Propanol on TiO2(110): Low- and High-Temperature Dehydration, Isotope Effects, and Influence of Local Surface Structure

摘要

Dosed on rutile TiO2(110) at 100 K, the thermal chemistry of 2-propanol in three forms-C_3H_7OH, C_3D_7OD, and C_3H_7OD-was characterized using temperature-programmed desorption. Only 2-propanol, propene, and water desorb with no evidence for acetone. The propene forms and desorbs by two paths, a heretofore unreported low-temperature path extending from 300 to 450 K and, concurring with prior work, a high-temperature path peaking between 570 and 580 K. Both paths exhibit isotope effects. The high-temperature path is interpreted in terms of decomposition of 2-propoxy species located on bridging oxygen atom rows. The low-temperature path is attributed to 2-propanol dehydration on undercoordinated Ti~(4+) ions of the Ti~(4+) rows. The low-temperature path characteristics vary with the long-range order and bridge-bonded oxygen atom vacancy concentration.