Electrochemical oxidation of graphite in an intermediate temperature direct carbon fuel cell based on two-phases electrolyte

As a promising intermediate temperature fuel cell, Direct Carbon Fuel Cell (DCFC) with composite electrolyte composed of Samarium-Doped Ceria (SDC) and a binary carbonate phase (67 mol% Li2CO3/33 mol% Na2CO3) has a much higher efficiency compared with conventional power suppliers. In the present work, SDC powder has been synthesized by an oxalate co-precipitation process and used as solid support matrix for the composite electrolyte. Single cell with composite electrolyte layer is fabricated by a dry-pressing technique using LiNiO2/Li2Na2CO3/SDC as cathode and 1:9 (weight ratio) graphite mixture with 67 mol% Li2CO3/33 mol% Na2CO3 molten carbonate as anode. The cell is tested at 600–750 °C using electrolytical graphite mixture as fuel and O2/CO2 mixture as oxidant. A relatively good performance with high power density of 58 mW cm−2 at 700 °C is achieved for a DCFC using 0.8 mm thick composite electrolyte layer. The sensibility of the 1 cm2 DCFC single cell performance to the anode gas nature is also investigated. At temperatures higher than 700 °C, both carbon (C) and carbon monoxide (CO) can be considered as reacting fuel for the DCFC system.