Reduction of carbon dioxide

COUPLING OF ELECTRODE ELECTRON TRANSFERS WITH CHEMICAL REACTIONS 

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Besides chemical catalytic reduction of carbon dioxide with hydrogen, which is already possible in the laboratory, we are exploring a new approach to recycling carbon dioxide into methyl alcohol or related oxygenates via aqueous eleetrocatalytic reduction using what can be called a regenerative fuel cell system. The direct methanol fuel cell... 

The conventional electrochemical reduction of carbon dioxide tends to give formic acid as the major product, which can be obtained with a 90% current efficiency using, for example, indium, tin, or mercury cathodes. Being able to convert CO2 initially to formates or formaldehyde is in itself significant. In our direct oxidation liquid feed fuel cell, varied oxygenates such as formaldehyde, formic acid and methyl formate, dimethoxymethane, trimethoxymethane, trioxane, and dimethyl carbonate are all useful fuels. At the same time, they can also be readily reduced further to methyl alcohol by varied chemical or enzymatic processes. 

New Synthesis. Many attempts have been made to synthesize oxaUc acid by electrochemical reduction of carbon dioxide in either aqueous or nonaqueous electrolytes (53—57). For instance, oxaUc acid is prepared from CO2 as its Zn salt in an undivided ceU with Zn anodes and stainless steel cathodes ia acetonitrile containing (C4H2)4NC104 and current efficiency of >90% (53). Micropilot experiments and a process design were also made. 

The net result of photosynthesis is reduction of carbon dioxide to form carbohydrates. A key intermediate is phosphoglyceric acid, from which various simple sugars are produced and disproportionated to form other carbohydrates. 

Taniguchi, I. Electrochemical and Photoelectrochemical Reduction of Carbon Dioxide 20... 

The reduction of carbon dioxide is another of the basic electrochemical reactions that has been studied at modified electrodes. The reduction at Co or Ni phthalocyanine in acidic solution yields formic acid or carbon monoxide A very high selectiv-... 

Figure 8.8 Reduction of carbon dioxide with formate dehydrogenase and porphyrin complex using light energy [6h].

In particular, the photo(electro)chemical reduction of carbon dioxide is connected to one of the most important environmental problems necessitating an urgent solution, that is, the fixation of CO2 in the atmosphere. The feasibility of CO2... 

Benniston AC, Haniman A (2008) Artificial photosynthesis. Materials Today 11 26-34 Inoue T, Fujishima A, Konishi S, Honda K (1979) Photoelectrocatalytic reduction of carbon dioxide in aqueous suspensions of semiconductor powders. Nature 277 637-638 Halmann M (1978) Photoelectrochemical reduction of aqueous carbon dioxide on p-type gallium phosphide in liquid junction solar cells. Nature 275 115-116 Heminger JC, Carr R, Somorjai GA (1987) The photoassisted reaction of gaseous water and carbon dioxide adsorbed on the SrH03 (111) crystal face to form methane. Chem Phys Lett 57 100-104... 

Taniguchi I, Aurian-Blajeni B, Bockris O MJ (1983) Photo-aided reduction of carbon dioxide to carbon monoxide. J Electroanal Chem 157 179-182... 

Bockris O MJ, Wass JC (1989) The photoelectrocatalytic reduction of carbon dioxide. J Electrochem Soc 136 2521-2528... 

Kuwabata S, Nishida K, Tsuda R, Inoue H, Yoneyama H (1994) Photochemical reduction of carbon dioxide to methanol using ZnS microcrystaUite as a photocatalyst in the presence of methanol dehydrogenase. J Electrochem Soc 141 1498-1503... 

Reduction of Carbon Dioxide Electrocatalytic Properties of Carbon 19... 

Electrochemical reduction of carbon dioxide has found no extensive application so far, yet it is of great interest for scientists in the fields of theoretical and applied electrochemistry. To a certain extent, it is analogous to the photochemical carbon dioxide reduction, but it involves no chlorophyll and yields simpler products. In recent years some books and reviews on this topic have been published (e.g., Taniguchi, 1989 Sullivan et al., 1993 Bagotsky and Osetrova, 1995). 

Electrochemical reduction of carbon dioxide is usually conducted in aqueous or nonaqueous electrolyte solutions at cathodes made of various materials. As a result, various organic substances can form. The most common reactions are as follows ... 

The reaction products often compromise a mixture of various substances. Moreover, the reduction of carbon dioxide in aqueous solutions in the cathodic potential region is always accompanied by hydrogen evolution. Hence, an important criterion that describes the reaction selectivity is the faradaic yield ri for each individual Mh organic reaction product. 

Formates and carbon monoxide are products of a shallow reduction of carbon dioxide (two electrons per one CO2 molecule). In the last few years, much attention has been paid the problem of obtaining products of deeper reduction (e.g., methanol or methane) which may be used as fuels in engines or in fuel cells. 

The mechanism of carbon dioxide reduction in aqueous and nonaqueous solutions was investigated by several authors. It is now generally accepted that the reduction of carbon dioxide to formate ions is a multistep reaction with the intermediate formation of free radicals CO2 and HCO2 either in the solution or adsorbed on the electrode ... 

Summing up, it can be said that the reaction of the electrochemical reduction of carbon dioxide will be the subject of painstaking research for a long time to come. In the future this reaction is very likely to play an important role in the electrochemical industry. 

Bagotsky, V. S., and N. Osetrova, Electrochemical reduction of carbon dioxide, Russ. J. 

Taniguchi, L, Electrochemical and photoelectrochemical reduction of carbon dioxide, in Modem Aspects of Electrochemistry, J. Bockris et al., Eds., Vol. 20, Kluwer, New York, 1989, p. 327. 

Great promise exists in the use of graphitic carbons in the electrochemical synthesis of hydrogen peroxide [reaction (15.21)] and in the electrochemical reduction of carbon dioxide to various organic products. Considering the diversity in structures and surface forms of carbonaceous materials, it is difficult to formulate generalizations as to the influence of their chemical and electron structure on the kinetics and mechanism of electrochemical reactions occurring at carbon electrodes. 

It is relevant and, of course, not out of context to touch briefly on the technologies used for the reduction of carbon dioxide emissions from many origins, including several examples referred to in the present text. The up-swing in global temperature over the previous... 

However, process (6.5.5) cannot be a universal photosynthetic process because H2S is unstable and is not available in sufficient quantities in nature. Water is the only substance that can be used in the reduction of carbon dioxide whose presence in nature is independent of biological processes. 

The characterization and crystal structure of the dimer [Pt2( -dppm)3] (dppm = bis(diphenyl-phosphino)methane), first reported as a deep red complex in 1978, was described by Manojlovic-Muir et al. in 1986.11 The structure, the first of its type, is made up of two parallel and almost eclipsed trigonal-planar platinum moieties bridged by three diphosphine ligands. The Pf Pt separation is 3.0225(3) A, too long to be considered a bond.11 [Pt2(//-dppm)3] catalyzes the hydrogenation/reduction of carbon dioxide with dimethylamine to give dimethylformamide12 (Equation (1)) and the reverse reaction.13... 

Inoue, T., Fujishima, A., Konishi, S. and Honda, K. Photoelectrocatalytic Reduction of Carbon Dioxide in Aquesous Suspensions of Semiconductor Powders. Nature. 1979, 277 637. 

Kohno, Y., Hayashi, H., Takenaka, S., Tanaka, T., Funabiki, T. and Yoshida, S. Photo-enhanced reduction of carbon dioxide with hydrogen over Rh/Ti02. Journal of Photochemistry and Photobiology. 1999. A 126,117-123. 

Here, some recent studies of the electrochemical and photo-electrochemical reduction of carbon dioxide as well as some other related subjects will be reviewed and discussed. Attention is focused especially on the work done in the last ten years, to avoid duplication of previous review articles.2,4... 

A little later, Russell et al.19 tried to obtain methanol from carbon dioxide by electrolysis. Reduction of carbon dioxide to formate ion took place in a neutral electrolyte at a mercury electrode. On the other hand, formic acid was reduced to methanol either in a perchloric acid solution at a lead electrode or in a buffered formic acid solution at a tin electrode. The largest faradaic efficiency for methanol formation from formic acid was ca. 12%, with poor reproducibility, after passing 1900 C in the perchloric acid solution at Pb in a very narrow potential region (-0.9 to -1.0 V versus SCE). In the buffered formic acid solution (0.25 M HCOOH + 0.1 M... 

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