Development of a Press-Type Direct Carbon Fuel Cell for Higher and More Stable Power Output

Abstract

A triple phase boundary reaction site was formed in a direct carbon fuel cell (DCFC) when the char wetted by molten carbonate was in contact with the anode. It has been reported that gases such as CO 2 covered the anode during discharge, leading to high anode overpotential. In this study, a press-type DCFC was developed to overcome this issue. By pressing the perforated anode on the carbon/carbonate-packed bed, it was expected that the carbon particles would remain in contact with the anode, while the gas products would be released through the perforation due to their buoyancy. As a result, the power output achieved with the press-type DCFC was higher and more stable as compared with the conventional DCFC. The anodic impedance spectra showed that the arc size of the press-type DCFC was much smaller than that of the conventional DCFC. This was particularly noticeable at the low frequencies, indicating the anode resistance caused by the mass transfer processes including the gas products and the contact between the anode and carbon particles to be significantly less in the press-type DCFC.

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

“…A schematic of the press-type DCFC developed by our research group is shown in Figure . The details of conventional and press-type DCFCs are described elsewhere . The counter electrode (CE) and reference electrode (RE) were made from a circular gold plate (diameter of 13.5 mm and thickness of 0.5 mm) covered by a 100-mesh gold and a gold sheet with a height of 10 mm and a width of 5 mm, respectively.…”

“…The counter electrode (CE) and reference electrode (RE) were made from a circular gold plate (diameter of 13.5 mm and thickness of 0.5 mm) covered by a 100-mesh gold and a gold sheet with a height of 10 mm and a width of 5 mm, respectively. The gas products at the reaction sites in the conventional DCFCs simply remained around the anode, whereas these were released in press-type DCFC through the perforations as a result of their buoyancy . A quartz reactor was heated using an electric furnace, and argon was introduced into the reactor compartment during heating.…”

“…The CO 2 and CO production rates during discharge were measured in the constant current discharge, and the theoretical production rates were also calculated. When carbon is consumed through electrochemical oxidation of carbon (reaction ), the CO 2 production rate during discharge is calculated as follows: where F is the Faraday constant (96 450 C/mol), V m is the molar volume of CO 2 , and I is the constant current flow, and details are provided elsewhere. , …”

“…This lowered the performance of the conventional DCFC, in which the anode was inserted into the carbon/carbonate slurry. To overcome this issue, we developed a press-type DCFC, by pressing the perforated anode into the carbon/carbonate-packed bed, achieving a higher and more stable power output . The carbon/carbonate mixture was useful in the electrochemical conversion of solid carbon particles.…”

“…To overcome this issue, we developed a press-type DCFC, by pressing the perforated anode into the carbon/carbonate-packed bed, achieving a higher and more stable power output. 15 The carbon/carbonate mixture was useful in the electrochemical conversion of solid carbon particles. The design of the carbon/carbonate mixture is vital for improving the DCFC performance.…”