Impact of Mass Transfer in the Carbon/Carbonate-Packed Bed on the Power Output of a Press-Type Direct Carbon Fuel Cell

• Published in: Energy & fuels Vol. 33; no. 12; pp. 12865 - 12870
• Main Authors: Watanabe, Hirotatsu, Shimada, Takashi, Nakanouchi, Minori, Hanamura, Katsunori
• Format: Journal Article
• Language: English
• Published: American Chemical Society 19.12.2019
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/acs.energyfuels.9b03032

The power output of a press-type direct carbon fuel cell (DCFC) with the perforated anode pressed on the carbon/carbonate-packed bed was studied by correlation with impedance spectroscopy at different carbon loads. Image analysis of the solidified carbon/carbonate-packed bed showed that the filling ratio of carbon and the contact area between carbon and the anode linearly increased as the initial carbon load increased. The power output of the DCFC also increased with increasing the initial carbon load and became almost saturated at an initial carbon load of 3.0 wt %. This trend coincided with the anode side impedance spectra. At high current densities, the power output became unstable and a continuous discharge could not be achieved at an initial carbon content of 5.0 wt %. Although the press-type DCFC is designed to release gas products through its perforated anode, those products likely still remained around the anode at high current densities. Spaces between the carbon particles in the packed bed worked as a channel for ion diffusion. Therefore, gas products likely blocked this ion diffusion channel, narrowing with increasing the filling ratio of carbon. By linking the impedance spectra with the power output of the press-type DCFC, it was suggested that the ion diffusion process in the carbon/carbonate-packed bed played an important role for stable continuous discharge at high current densities.