The role of surface oxides in formic acid oxidation on Au |
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Authors: | J.O. Besenhard Roger Parsons R.M. Reeves |
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Affiliation: | Department of Physical Chemistry, The University, Bristol BS8 1TS England |
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Abstract: | Compared to Pt or Pd electrodes, Au is a poor catalyst for the direct anodic oxidation of HCOOH, but the formation of Au surface oxides in acidic solutions is accompanied by a fast oxidation of HCOOH. This fast reaction is not simply a secondary reaction of Au surface oxides since those oxides are kinetically stable in HCOOH solutions. They do oxidize HCOOH only via a slow and purely electrochemical process which occurs on free Au sites and is “driven” by oxide reduction. The fast HCOOH oxidation is due to a highly reactive intermediate which is able either to form stable Au oxides AunOm or to react with HCOOH. Our results are consistent with the model that by the charge transfer step a reactive non-equilibrium {Au…O> species is formed which converts to stable equilibrium oxides AunOm after migration and rearrangement steps. Pre-equilibrium oxidizes HCOOH and this oxidation is of lower order with respect to compared with the formation of AunOm. |
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