Carbon dioxide (CO2), known as a greenhouse gas, has been released substantially into the atmosphere due to fossil fuel combustion by human activities. Exceptional amounts of CO2 will cause global warming and climate change, resulting in an irreparable loss of biodiversity and habitat. However, CO2 could be used as an abundant C1 feedstock for renewable energy storage. The reduction of CO2 is hard to achieve due to its kinetic and thermodynamic stability. Existing catalysts such as transition metal and metal complexes suffer from either low selectivity or low CO2 conversion efficiency. Biocatalysts are an attractive alternative because of their high selectivity, low overpotential and ability to function at mild conditions. Recently developed molybdenum dependent formate dehydrogenase (Mo-FDH) from Escherichia coli has high efficiency to interconvert formate and CO2. However, the direct electron transfer of Mo-FDH is inefficient, and so far, no immobilized mediating system has been designed with Mo-FDH to support CO2 reduction. Reductive redox polymers are rare due to a limited number of mediators and stability issues. Here we developed a reductive redox polymer (cobaltocene modified poly allyl amine; Cc-PAA) by a facile method, to wired Mo-FDH at the electrode surface and simultaneously mediate electrons to facilitate CO2 reduction. Formate, confirmed by NMR and a secondary enzymatic assay, is the exclusive product. This electroenzymatic interface can reduce CO2 at a mild applied potential (-0.66 V. vs SHE) with a high Faradaic efficiency (99 ± 5%). Reductive redox polymers, when coupled with enzymatic systems, can catalyze previously unattainable reduction reactions which are useful to a broad scientific community. It has huge potential to design mediating systems for enzymatic N2 reduction to NH3 and H+ reduction to H2. Therefore, the system described here is likely to produce even more interesting developments in the future.

Designing electroenzymatic interface for CO2 reduction

2019 Spring National Meeting

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