Direct Carbon Fuel Cells

Abstract

Direct carbon fuel cells (DCFCs) are high temperature fuel cells which offer the possibility to directly convert the chemical energy of carbon materials (e.g. coal, lignite, char, carbonized biomass) into electricity. In addition to using solid carbon fuels, higher overall efficiencies should be possible because the thermodynamic efficiency is close to 100 %. This means higher than those of conventional fuel cell types for gaseous fuels. DCFC technology can employ three different electrolyte types: Molten carbonate electrolyte (liquid salt), molten hydroxide electrolyte (liquid salt) and solid oxide electrolyte (solid ceramic layer). Recently, also combined technologies have been developed. In this chapter, all the concepts are described and their advantages and difficulties are discussed.

Development of a Low Temperature, Molten Hydroxide Direct Carbon Fuel Cell

“…Carbon fuel corrosion occurs due to reaction with product CO 2 in the anode via the reverse Boudouard (or CO 2 gasification) reaction. Because this is an endothermic reaction, the equilibrium CO concentration increases with temperature; e.g., 25% at 600 °C, and 90% at 800 °C . Vutetakis et al .…”

Renewable Gas

“…The first part would use a thermochemical technique to draw off the hydrogen-rich volatiles as a fuel, aiming to leave a carbon-rich residue such as biochar or pure biocarbon, and this carbon-rich by-product would then be used to make electricity via electrochemistry -in a Direct Carbon Fuel Cell (DCFC) (Desclaux et al, 2010). If the concentrated carbon dioxide exit gas were to be sequestered, in total this hybrid system would be carbon-negative.…”

“…The use of fuel cells, for example, DCFC, for the processing of waste could be envisaged where the feedstocks are high in carbon, such as plastics (Desclaux et al, 2010), and are pre-processed into fine grains to permit efficient reaction contact surface area.…”

Samaria-Doped Ceria Electrolyte Supported Direct Carbon Fuel Cell with Molten Antimony as the Anode

“…According to the different electrolytes, DCFCs can be mainly grouped into three types, i.e., molten hydroxide, − molten carbonate, − and solid oxide electrolyte fuel cells. − Recently, lots of research has been carried out on DCFCs using solid oxide electrolytes (based upon solid oxide fuel cells, SOFCs) to separate the cathode and anode because advanced cathode materials can be used in these structured DCFCs. However, utilization of solid carbon fuels directly inside these fuel cells still presents serious challenges largely because of the difficulty in making physical contact between the fuel particles and charge-transfer reaction sites at the anode/electrolyte interface. − Various approaches were employed to improve the anode performance of the DCFC by adding different intermediaries into the anode chamber, including dispersing solid carbon in molten carbonate − ,,,, or molten metal − ,, in the anode compartment. Although molten carbonates exhibit high ionic conductivity at elevated temperature, they are poor electrical conductors that limit the performance of these cells.…”