Hybrid direct carbon fuel cell anode processes investigated using a 3-electrode half-cell setup

A 3-electrode half-cell setup consisting of a yttria-stabilized zirconia (YSZ) electrolyte support was employed to investigate the chemical and electrochemical processes occurring in the vicinity of a model hybrid direct carbon fuel cell (HDCFC) anode (Ni-YSZ) in contact with a molten carbon-alkali carbonate slurry. Electrochemical testing, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), with and without the Ni-YSZ layer highlighted the promotional effect of the Ni-YSZ anode layer, and revealed the contributions of Ni/NiO, and potentially K/K2O, redox couple(s). Treated anthracite and bituminous coals, as well as carbon black, were tested, revealing similar open circuit potential and activation energies in mixed 96–4 vol% N2–CO2 and 50–50 vol% CO–CO2 environments between 700 and 800 °C. Bituminous coal showed the highest activity, likely associated to a high O/C ratio and hydrogen content. Based on acquired data, a reaction scheme was proposed for processes at the working electrode, including the role of bubble formation in the vicinity of the electrochemically active solid/molten medium interface.This work was funded in part by the European Commission Research Fund for Coal and Steel, as the Efficient Conversion of Coal to Electricity – Direct Coal Fuel Cells project (RFC-PR-10007), in collaboration with the University of St. Andrews, University of Western Macedonia, and the Spanish Instituto Nacional del Carbón (INCAR). Additional funding was supplied by the Department of Energy Conversion and Storage at the Danish Technical University (DTU)-Risoe Campus. We extend our thanks to M. Nielsen, A. Petersen and F. Vico, as well as to Drs. C. Graves, P. Holtappels, D. Ippolito, M. Mogensen, and S. Veltzé at the DTU Department of Energy Conversion and Storage for all assistance.Peer reviewe