(182e) Amine Promotion of CO2 Conversion for Artificial Photosynthesis

The objective of our work is to learn how to use artificial photosynthesis to create feedstocks for renewable fuels. We imagine collecting electricity via a series of mirrors and a solar panel and using the electricity to convert CO2 and water to CO, H2 and formic acid. At present the limiting factor in these processes is the ability to convert CO2. So far one can only obtain reasonable efficiencies by using a catalyst like mercury at high overportentials, and even then the efficiency is low. Instead most of the electrons go to electrolyzing water.

We have been exploring the use of amines to suppress water electrolysis and enhance CO2 electrolysis. We find that choline chloride raises the onset of hydrogen evolution by about 0.5 volt, and lowers the overpotential for CO2 conversion by a similar amount. The result is that there is a region of potential where CO2 electrolysis is more rapid than hydrogen evolution. The products vary with the catalyst with CO evolution dominating on nickel catalysts, and formic acid dominating on palladium catalysts. More work needs to be done, but it appears that this work will lead to a practical route for artificial photosynthesis.