Exploration of New Applications of Inductively Coupled Plasma Mass Spectrometry (ICPMS) to Fuel Cell Electrochemistry
The electrochemically active surface area of catalysts in fuel cells can be increased using nanoparticles (NPs). To assess their stability, the mass concentration and the size of NPs, along with the portion that is dissolved, must be determined. Inductively coupled plasma mass spectrometry (ICPMS) allows ultra-trace analysis of solutions and, in single particle (sp) mode, can measure the mass of inorganic NPs in aqueous medium. In fact, if the shape, density and composition of the NPs are known, their masses can be converted into sizes, and a size distribution can then be readily obtained. This thesis presents simple ways to extend the capabilities of ICPMS for the analysis of electrolyte and NPs. Firstly, it demonstrates that spICPMS can accurately characterize synthetic 10-nm Pt NPs and that it nicely complements transmission electron microscopy (TEM), which provides the NPs shape from their two dimensional projection. For a known shape, spICPMS measures the NPs size distribution much faster than TEM. Secondly, it introduces flow injection (FI) coupled to spICPMS, i.e., FI-spICPMS, which is then validated through the accurate characterization of 60 nm Au NPs standard suspension. Thirdly, FI-spICPMS is applied for the first time to synthetic Ni NPs and its performance is compared to that of spICPMS, TEM and X-ray diffraction. FI-spICPMS is beneficial over spICPMS as it eliminates the need to measure the transport efficiency and the sample uptake rate in order to determine the mass of NPs. Fourthly, a correction factor to the transport efficiency is proposed to improve the accuracy of spICPMS based on conventional standard solution calibration for ICPMS instruments exhibiting a significant settling time compared to the dwell time used to measure NPs. The suitability of the correction factor is confirmed through the accurate analysis of standard Au NPs. Finally, for the first time, mono-segmented flow analysis (MSFA) is coupled to ICPMS to facilitate the analysis of volume-limited and corrosive samples: 0.5 M H2SO4 electrolyte collected during cyclic voltammetry under simulated fuel cell conditions and minute amounts of differentially glycosylated purple acid phosphatase glycoforms. In the latter case, such amounts were insufficient for analysis by analytical service laboratories.
URI for this recordhttp://hdl.handle.net/1974/25923
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