We have previously demonstrated that pyridinium is electrocatalytic for the reduction of CO2 to methanol and related C1 products at certain metal and semiconductor electrodes. In our earlier work, we speculated that the electrocatalytic mechanism proceeded through the one-electron reduction of the pyridinium ring to form a pyridinyl radical. However, recent theoretical work by Batista along with experimental work in our labs suggests that reduction of pyridinium at a platinum electrode initially involves the reduction of the acidic proton to generate a surface hydride. This finding is supported by a recent report out of Saveant's laboratory. We suspect that this surface hydride is the primary agent in the reduction of CO2 as suggested by Batista. At other electrode interfaces, the initial reduction of pyridinium may involve other intermediates, including the initially speculated pyridinyl species as supported by Musgrave's theoretical analysis, or a dehydropyridinium, proposed by Carter and Keith. Reaction of CO2 with these various intermediates is then expected to generate formate via a variety of two-electron transfer pathways. In some cases, formate reduction proceeds to generate formaldehyde followed by methanol. Here we consider the details of the proposed reaction mechanisms provided by the researchers noted above in light of our experimental findings. We find that the details of the reactivity are both dependent on the electrode material and the exact pyridinium species employed. Evidence suggests an important role for electrolyte pH in the vicinity of the electrode interface. Independent of the specifics of the mechanism, we continue to support the finding that pyridinium is electrocatalytic for the reduction of CO2 at low overpotential.

Pyridinium as an electrocatayst for the reduction of carbon dioxide to C<sub>1</sub> products: Mechanistic considerations

248th National Meeting (2014)

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Pyridinium as an electrocatayst for the reduction of carbon dioxide to C1 products: Mechanistic considerations

Pyridinium as an electrocatayst for the reduction of carbon dioxide to C₁ products: Mechanistic considerations