NEXAFS FINGERPRINTING OF TIO2(110)-SO2

Polarisation-dependent S K-edge NEXAFS has been used to monitor the progression of the thermally-activated reaction between TiO2(110) and SO2.SO2 chemisorbs at 105 K, reacting to form a surface sulphate-like species as the substrate is heated to greater-than-or-equal-to 135 K. This is the final reaction product, having a coverage of 0.1 ML up to at least 450 K. A sulphite-like species is identified as an intermediate in this reaction, having a maximum concentration of approximately 0.2 ML at 155 K. Structural models are suggested in which SO2 initially bonds to Ti sites, subsequently forming complex anion-like species by incorporation into the raised row of bridging O atoms.