Monday, November 8, 2010: 10:36 AM
254 C Room (Salt Palace Convention Center)
For HCOOH, H2C(OH)2, and CH3OH, the oxidation reaction mechanism depends on Pt surface geometry, reactant molecular structure, and potential. All these are related to the strength of interaction between Pt&H, Pt&C, Pt&O, and the hydrophilic C-OH / hydrophobic C-R interaction with H2O. Strong Pt&H and Pt&C interaction facilitates the dehydrogenation and adsorption to C end, e.g. *COOH / *CH(OH)2. Further with strong P&O interaction, or/and hydrophobic C-R&H2O repulsion enhanced dehydration of C-(OH)2, *CO / *CHO formation is catalyzed. On the other hands, with relatively weaker Pt&C and Pt&H interaction yet adequately strong Pt&O interaction, adsorption into *OCHO* or *OCH2O* is easier. *OCHO* and *OCH2O* could compete with H2O* and *OH. Hence at high potential *CO oxidation is delayed due to more difficult formation of *OH. However at low potential the surface catalyzed C-OH cleavage from *COOH / *CH(OH)2 is also slowed down, resulting more selective direct CO2 pathway via deprotonation of O-H to surrounding H2O. Lastly, depending on the (110) step density on (111) terrace, the formation / cleavage of C-OH, and hence direct alcohol to carboxylic acid via *CR(OH)2 or *CRO pathway is catalyzed. This clear understanding is obtained through a systematic critical analysis over literatures that are often too specified to allow general mechanism understanding.