Alkaline research challenges

The history of alkaline fuel cells (AFCs) is a story of discoveries in basic science posing a challenge to applied research and technology development, a story of 100 years of experiments and false starts that finally led to the first practical fuel cell in the 1930s [1]. 

Acetate is often the main product of the ethanol oxidation reaction. However, for concentrated alkaline solutions, side products are formed, including polymerized acetaldehyde and carbonate. Polyacetaldehyde is regarded as an unwanted by-product because it coats and blocks the catalyst layer. The complete oxidation of ethanol to carbonate is highly desired because it doubles the number of electrons per reagent molecule. The catalytic cleavage of the C-C bond in aqueous media is a challenging task in catalyst research. At DLR, this is a research topic in collaboration with the University of Diisseldorf [31, 32]. 

Because carbonylation is a process of high practical importance, considerable work has been done on developing a recyclable biphasic protocol. Carbonylation is a hard challenge for this task, because, similar to the case of the Heck reaction, this process leads to the formation of salts, which irreversibly change the composition of the aqueous catalyst-containing layer and lead to its degradation. Besides, the products of hydroxycar-bonylation, the carboxylates, are soluble in water and must be recovered from alkaline solution. Acidification leads to the formation of an additional amount of salt. Therefore, in spite of extensive research, the recyclability of the systems developed so far is only modest. Rarely can more than a single reuse be achieved. 

While the existence of such kinds of sites is now accepted by most researchers in this field, several years ago they were challenged by the finding that also virtually metal-free catalysts are good ORR catalysts in acid and even more in alkaline solution. These catalysts, however, needed the presence of a metal like Fe dming catalyst synthesis by chemical vapor... 

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