Intermediate Temperature - SOFCs: Nanoparticles Synthesis through Coprecipitation By Nitrate Route and By Oxide Route

Solid Oxide Fuel Cells (SOFCs) are very promising devices to generate electrical energy for stationary applications as auxiliary power units for several purposes such as electrical grids, smart grids, cogeneration in different industrial processes, and also for transport, using mainly hydrogen and alternative fuels as syngas with high H₂ - content. Additionally the SOFCs have the advantage of a high efficiency considering cogeneration (80-93%) and also this technology produces minimal pollutant emissions.

Despite of enormous progresses made to date, this technology has to reach all technical requirements in order to be competitive. In this sense, the SOFCs must operate at intermediate temperatures (450 – 650 °C) instead high temperatures (around 1000°C). To reach this objective the research of the chemical routes to synthesize the catalysts for anode and cathode, and also the electrolyte is a key step to achieve the best electrochemical behavior of SOFCs operating at intermediate temperatures.

The electrochemical and mechanical properties of anode, cathode and electrolyte oxides for SOFCs are primordially determined by the chemical synthesis route. In this work a comparison between two coprecipitation routes is presented using: i) nitrates and ii) oxides. These synthesis routes were tested for the anode (nickel oxide – NiO), the cathode (lanthanum strontium cobalt ferrite - LSCF) and the electrolyte (gadolinium and samarium doped ceria – GDC and SDC, respectively).

For these four compounds (NiO, LSCF, GDC and SDC) the physical characterization consisted in SEM – morphology analysis. Also the crystal structure and the nanoparticle size is determined by X-ray diffraction (XRD). The chemical characterization is carried out using energy-dispersive analysis (EDS). In addition to the physical and chemical characterization a symmetrical two-electrode electrochemical test cell is tested in the range of intermediate temperatures (450 – 650 °C).

These two routes of synthesis by coprecipitation are compared determining the most suitable and economical method to produce anodic, cathodic and electrolytic powders oriented to a better electrochemical behavior for intermediate-temperature solid oxide fuel cells (IT-SOFCs).