Performance evaluation of a tubular direct carbon fuel cell operating in a packed bed of carbon

Abstract

The DCFC (direct carbon fuel cell) technology, based on the direct electrochemical oxidation of carbon, has the potential to double the electric efficiency and half the CO2 emissions compared to conventional coal fired power plants. In order to assess the scalability of the technology in terms of fabrication and fuel feed system, and to elucidate the possible causes of the cell degradation, a tubular DCFC has been fabricated and operated in a pulverised carbon packed bed at around 800 °C. The cell was operated for a total period of 11 days with many thermal cycles. The electrochemical impedance spectroscopy was used to elucidate the possible causes of the cell degradation. Post-mortem analysis of the cell with SEM (scanning electron microscopy) and XRD (X-ray diffraction) confirmed structural stability of both air and fuel electrodes. A peak power density of 30 mW cm−2 was obtained by direct contact of carbon to the fuel electrode with high purity He as the purge gas. The cell, at the end of operation was still found to produce 60% of the power relative to the power at the beginning of operation, and this study demonstrates the feasibility of continuous operation of the tubular fuel cell in a packed bed of carbon.