Electrochemical Oxidation of Carbon Monoxide

Gilman S. 1964. The mechanism of electrochemical oxidation of carbon monoxide and methanol on platinum. II. The reactant-pair mechanism for electrochemical oxidation of carbon monoxide and methanol. J Phys Chem 68 70-80. 

In Chapter 2, the electrochemical oxidation of carbon monoxide, which is considered as the key intermediate for methanol oxidation, is investigated using electrochemical and spectroscopic methods for polycrystalline and single crystal platiniim electrodes. In Chapter 3, the electrochemical oxidation of methanol on the same electrodes was treated. In Chapter 4, electrocatalytic activities of platinum modified by adding secondary elements will be disciissed. 

This section addresses the role of chemical surface bonding in the electrochemical oxidation of carbon monoxide, CO, formic acid, and methanol as examples of the electrocatalytic oxidation of small organics into C02 and water. The (electro)oxidation of these small Cl organic molecules, in particular CO, is one of the most thoroughly researched reactions to date. Especially formic acid and methanol [130,131] have attracted much interest due to their usefulness as fuels in Polymer Electrolyte Membrane direct liquid fuel cells [132] where liquid carbonaceous fuels are fed directly to the anode catalyst and are electrocatalytically oxidized in the anodic half-cell reaction to C02 and water according to... 

This opens up possibilities for an indirect electrochemical utilization of huge coal reserves. The possibility of direct electrochemical oxidation of carbon monoxide was soon questioned. It was suggested that hydrogen, rather than the carbon monoxide, is involved in the electrochemical reaction after being formed from CO by the Boudouard reaction ... 

Van Baar, J.F., J.A.R. Van Veen, J.M. Van der Eijk, T.J. Peters, and N. De Wit (1982). Electrochemical oxidation of carbon monoxide with carbon-supported Group VIII metal chelates Mechanistic aspects. Electrochim. Acta 27(9), 1315-1319. 

Figure 16.1. The energy level of carbon monoxide molecules, and the formation of metal-carbon monoxide bonding [449]. (Reprinted from Grgur BN, Markovic NM, Lucas CA, Ross PN. Electrochemical oxidation of carbon monoxide from platinum single crystals to low temperature fuel cells catalysis. Part 1 carbon monoxide oxidation onto low index platinum single crystals. J Serb Chem Soc 2001 66 785-97. With permission from the Serbian Chemical Society.)...

The possibility of a direct electrochemical oxidation of carbon monoxide was soon questioned. It was suggested that hydrogen, rather than carbon monoxide. 

The presence of defects opens new pathways which significantly decrease the thermal stability of the reconstructed Rh(llO) surfaces [39]. Although the activity of electrochemical oxidation of carbon monoxide and methanol electro-oxidation can be increased by increasing surface steps on Pt nanoparticles, the oxygen reduction reaction activity of the 2-nm-sized Pt nanoparticle has been found insensitive to the step area, as shown in Fig. 20.3 [40], in contrast to the methanol oxidation reaction activity. 

Carbon dioxide, formed by the water gas shift reaction (Eq. (7)) and by electrochemical oxidation of carbon monoxide (Eq. (6)), present in the exit gas leaving the anode, can be recirculated in the fuel supply at the cell inlet. It is well known that CO2 can act as an oxidant for hydrocarbons in the presence of a suitable catalyst, so called dry reforming (Eqs. (9) and (10) for methane and a general higher hydrocarbon, respectively) [38,39,42,43] ... 

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