• Energy Research

Abstract In order to adapt the anodisation technique to SOFC application, zirconium and zirconium–niobium alloys were tested in various electrolytic media and applied potentials (up to 420 V). The elaborated ZrO 2 insulating layers were characterised in situ by electrochemical impedance spectroscopy and their thicknesses were determined as ranging up to 1 μm. The effect of thermal annealing treatment of layers prepared in various experimental conditions was investigated by X-ray diffraction (XRD) and solid-state electrochemical impedance spectroscopy in a planar configuration. The effect of the growing conditions on significant parameters such as zirconia crystallite size, zirconia conductivity and activation energy were deduced up to 800 °C. The possibility of using the anodisation process for fuel cell devices is discussed. This study demonstrates that it surely requires the use of more efficient dopants, such as yttria.

Solid oxide fuel cell (SOFC) is a mature opportunity for producing power energy in remote areas like islands, where access to the electrical grid is not favoured, and gas distribution is the only viable approach. In this context, generally, biogas represents the most convenient fuel resources in these areas. However, the direct use of biogas in SOFCs is still an issue to be solved due to its negative effect on the conventional Ni-YSZ anode. In this study, to overcome this issue, we suggested using a protective layer coated on the anode of a commercial SOFC. A nickel manganite showing mixed ionic and electronic conductivity tailored specifically for this approach was investigated. The preliminary characterisations showed that the formation of a Ruddlesden-Popper (RP) n ¼ 1 structure supporting fine encapsulated particles based on Ni was formed around 800 C in consequence of the reducing environment. The electrochemical experiments carried out for 270 h demonstrated for the coated cell significant stability in the presence of dry biogas, albeit an ageing effect was noticed in the electrical percolation of both cell electrodes. The post mortem analyses revealed an attractive redox property for the nickel manganite, which partially returned to the RP n ¼ 2 phase. Moreover, the absence of carbon deposits on the anode suggests possible applications for this approach.

One step electrochemical deposition of Cu-In-Ga mixed oxide precursor film on Mo substrate is carried out by potentiostatic method in an acidic nitrate based electrolyte. Deposition parameters, such as ions concentration, deposition time and potential, enable to control accurately the layer composition and thickness. The oxide layer is subsequently transformed into metallic alloy by thermal reduction, and selenized into Cu(In,Ga)Se2 compound. First cell results show conversion efficiency up to 9.4%.