Development of Ir Nanocatalysts As CO2-Tolerant Anodes in Electrochemical Hydrogen Pumps for H2/CO2 Separation

Recently, various CO₂ capture and storage (CCS) technologies have been actively researched and developed. As CO₂ sources usually produce mixtures that contain other gases such as H₂ and H₂O, gas separation technologies are required to increase the efficiency of CCS processes, and the electrochemical hydrogen pump is expected to be effectively utilized for H₂/CO₂gas separation. Electrochemical hydrogen pumps will be suitable for the treatment of gas mixtures produced from coal gasification and steam-reforming processes, as well as the anode outlet gases from molten carbonate fuel cells integrated with fossil fuel power plants.

As electrocatalysts for electrochemical hydrogen pumps, carbon-supported Pt nanoparticles have been widely used for hydrogen compression [1] and hydrogen separation from gas mixtures [2, 3]. However, as Pt surfaces can be severely poisoned by the strong adsorption of CO molecules that are generated through the reverse water-gas shift reaction of CO₂ and adsorbed hydrogen [4], the Pt catalyst in the anodes can be largely deactivated when H₂/CO₂gas mixtures are supplied to electrochemical hydrogen pumps.

In this study, we synthesized Ir-based nanocatalysts for the application of hydrogen separation from CO₂-rich mixture gas and characterized them by XRD, XPS, TEM, and TGA. The electrochemical characteristics of Ir-based nanocatalysts were investigated by half-cell and single-cell tests, focusing on poisoning under CO₂ atmosphere. The Ir-based catalyst demonstrated higher HOR/HER activity than the commercial Pt catalyst, and, by CO₂ stripping analysis, it was confirmed that the CO poisoning under CO₂ atmosphere was much smaller for Ir-based catalysts. As a result, enhanced hydrogen pump performances could be achieved with the anode feed of H₂/CO₂mixture.

References

[1] K. Onda, K. Ichihara, M. Nagahama, Y. Minamoto, T. Araki, J. Power Sources, 164, 1 (2007).

[2] B. Ibeh, C. Gardner, M. Ternan, Int. J. Hydrogen Energy, 32, 908 (2007).

[3] C.L. Gardner, M. Ternan, J. Power Sources, 835, 171 (2007) -841.

[4] N. Hoshi, T. Izuwra, Y. Hore, Electrochim. Acta,  40, 883 (1995) -887.