A Novel Anion Exchange Membrane Enabling Generation of Syngas from Water and Carbon Dioxide at Industrially Important Rates

The electrochemical production of syngas would enable production of transportation fuels from carbon dioxide (CO₂), water and renewable energy, but a suitable process does not exist.  CO₂ reduction to carbon monoxide (CO) has been a particular problem, in that high overpotentials are often needed to drive the CO₂ reduction process, so the cost of the process was too high to be economic. Recently, we discovered a helper catalyst, an imidazolium-based ionic liquid (IL), by which CO₂ can be reduced to CO at an overpotential as low as 0.17 V on silver (Ag) particle catalysts [1]. The IL suppresses hydrogen evolution on the Ag electrode to a degree tunable by modifying, for instance, the pH and water content of the IL electrolyte.

In previous work, the currents were too low to be practical.  In the present paper, we present results using a newly developed DX4-13 membrane.   We find that the new membranes allow us to obtain 300 mA/cm² of CO current at room temperature and atmospheric pressure. 

We also find that by changing the membrane composition, or varying the pH, we can produce syngas from a single electrolyzer. We have observed syngas production from a single cell running at room temperature at 100 mA/cm² total current, however H₂production is reduced at higher currents due to CO poisoning of the hydrogen production process.   These and other results will be discussed.     

[1] Rosen, B. A.; Salehi-Khojin, A.; Thorson, M. A.; Zhu, W.; Whipple, D. T.; Kenis, P. J. A.; Masel, R. I.  Science, 2011, 334, 643.