Electrochemical oxidation of carbon monoxide with carbon-supported group VIII metal chelates: mechanistic aspects

✍ Scribed by J.F. van Baar; J.A.R. van Veen; J.M. van der Eijk; Th.J. Peters; N. de Wit

• Publisher: Elsevier Science
• Year: 1982
• Tongue: English
• Weight: 485 KB
• Volume: 27
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(82)80154-0

✦ Synopsis

The electrochemical oxidation of carbon monoxide with carbon-supported Group VIII transition-metal chelates has heen studied both in acid and in alkaline electrolyte. The systems based on Rhand b-porphyrins emerge as outstanding electrocatalysts in aqueous acid solutions, whereas in strongly alkaline media the Co and Fe counterparts appear to be excellent catalysts as well. By analogy with the behaviour of homogeneous catalysts for the water gas shift reaction, it is proposed that the catalytic cycle consists in essence of the following steps: (i) CO adsorption on an isolated metal centre, (ii) nucleophilic attack by H,O (acid) or OH (alkaline solution) on the adsorbed CO molecule, and (iii) decarboxylation. It turns out that the activity of each catalyst, and the mechanism whereby it oxidizes CO, can be straightforwardly explained in terms of both the redox properties of the metal centre and the CO affinity of the metal ion in-various oxidation states.