For in-situ gas analysis.
Developed for in-situ gas analysis of battery materials in a flow-through set-up the PAT-Cell-Gas features a gas inlet and outlet with self-locking couplings that are compatible with 1/16 in. Swagelok tube fittings. Optional built-in pressure sensor or valve port for gas sampling with a syringe are also available.
The PAT-Cell-Gas combines all capabilities of the ECC-Air, ECC-DEMS and PAT-Cell-Press test cells.
The cell stack is placed on top of a perforated or grooved current collector (flow field), which is to be purged with a gentle stream of gas. The lower electrode must be gas permeable, so as to allow for gas exchange with the feed gas. Typically, the cell is used with gas diffusion electrodes (such as for Li-air) or with Li-ion battery electrodes with a meshed current collector. This special design minimizes backmixing of the gas from the flowfield back into the headspace, and is thus very suitable for time-resolved gas analysis with a mass spectrometer, for example.
All PAT-Cell-Gas variants can be operated directly with the PAT-Tester-x potentiostat. If used with a 3rd party potentiostat, the PAT-Press-Box is required for all variants equipped with a pressure sensor.
There are two standard lower plungers available: a perforated plate (larger volume flows of gas) and spiral flow-field (best time resolution for analysis such as as mass spectrometry)
Mode 1: Air mode
The lower plunger with perforated plate allows for electrochemical characterization of gas diffusion electrodes used for instance in Li-air batteries. The lower electrode is contacted by and “breathes” through the perforated stainless steel current collector supporting it. During operation, the pressure gradient building up between cell headroom and the gas volume below the perforated plate effectively prevents back-mixing. The relatively large volume below the perforated is at the expense of time resolution, but makes this solution robust against clogging of the gas path.
Mode 1: OEMS mode
The PAT-Core setup using a lower plunger with flow field provides almost perfect plug-flow of the purge gas being essential for quantitative time-resolved analysis. Gases evolved or consumed at the working electrode may be analysed through the composition change of the gas stream that is to be passed along the spiral-type flow field below the working electrode. The composition of the outgoing gas can be analyzed by e.g. mass spectrometry. The pressure gradient between cell headroom and spiral-type flow field effectively prevents back-mixing. This and the tiny gas volume of the flow field ensure best possible time resolution.