Novel characterization method of ceria-based catalyst and electrode in solid oxide fuel cells

Abstract

Due to the worldwide rising awareness for environmental protection, there is a needfor novel energy sourceswith high efficiency and low pollutant emission. Solid oxide fuel cells (SOFCs) have received more and more attention for their ability to fulfill such requirementsand theirfuel flexibility. Materials with mixed ionic and electronic conductivity (MIEC) have emerged to be a promising class of candidates for SOFCs’ electrodes. However, due to the participation of dual-phase boundary and the resulting complex electrochemical and chemical reaction mechanism, the knowledge on the properties of MIEC materials is still insufficient. Therefore, it is difficult to quantitatively assess the relation of microstructures and performance of MIEC electrodes and efficiently improve the design strategy. In this thesis, efforts are made on the development of characterization method for gadolinium-doped ceria anode for SOFCs, to investigate the mechanism of hydrogen and methane reaction on the electrodes and the relationship between the performance and microstructures. A meliorated methane pulse transient experiments is first performed onimpregnated Ni/CGO catalyst along with in-situ Raman spectroscopy. Through qualitative and quantitative analysis of the peaks, the mechanism of methane oxidation on Ni/CGO is revealed. Furthermore, the relationship of Ni surface area, CGO oxidation state,CGO surface oxygen with the methane uptake and carbon resistance is revealed. This implication is further applied in combined with electrochemical impedance spectroscopy in the characterization of aged Ni/CGO electrodes, to investigate the influence of aging to its performance. The influence of co-impregnation of Cu is also investigated via methane pulse transient experiment. In the final chapter, a general approach of deconvoluting the DPB and TPB processes in MIEC electrodes is developed and applied to summarize a general design strategy for this class of materials. According to the strategy a novel structure is synthesized and shows better performance compared with conventional structures.