The electrochemical study of NixCe1−xO2−δ electrodes using natural gas as a fuel

Abstract

Solid oxide fuel cells (SOFCs) enable the direct electrochemical conversion of hydrocarbon-based fuels, such as natural gas, to electricity with high efficiency. Nevertheless, the direct utilization of natural gas in the presence of Ni-based anodes is still challenging as it causes severe deposition of carbon (coke). An excellent doping matrix is the ceria (CeO₂), which can lose oxygen without altering its structure. In this study, Ni_xCe_1−xO_2−δ, where x = 0.2, 0.4, 0.6 or 0.8, is prepared using a sol–gel technique. The XRD results confirm the cubic structure of the prepared samples. The SEM analysis shows the porous and inhomogeneous nature of the particles with calculated sizes from ∼22.83 to ∼119 nm. The FTIR verifies the presence of nitrates in all the prepared anodes. UV-Vis spectroscopy demonstrates that the bandgap and optical constants decrease with increasing Ni content up to x = 0.6. The thermodynamic parameters of Ni oxidation and carbon formation are employed to study the reforming of natural gas in a SOFC system. Among the four samples, Ni_0.6Ce_0.4O_2−δ possesses the highest electronic conductivity (∼5.97 S cm⁻¹) at 650 °C and a low activation energy of ∼0.120 eV, which indicates good catalytic activity with enhanced electrochemical performance for the SOFC. A maximum power density of ∼386 mW cm⁻² is obtained for NDC3 at 600 °C, which is comparable to those of other prepared electrodes. The electrochemical impedance spectrum (EIS) of NDC3 was also analysed in a hydrogen atmosphere at 600 °C. Thus, Ni-doped ceria can be considered a potential anode material for SOFCs due to its efficient and excellent catalytic properties, ease in redox-based reactions, and improved resistance against the formation of coke.