High temperature co-electrolysis of steam and carbon dioxide using a solid oxide cell (SOC) has been shown to be an efficient route to produce syngas (CO + H2), which can then be converted to synthetic fuel. Optimization of co-electrolysis requires detailed understanding of the complex reactions, transport processes and degradation mechanisms occurring in the SOC during operation. Thermal imaging, Raman spectroscopy and Diffuse Reflectance Infrared Fourier Transform Spectroscopy are being developed to probe in-situ both the reactions occurring during operation and any associated changes within the structure of the electrodes and electrolyte. Here we discuss the challenges in designing experimental apparatus suitable for high temperature operation with optical spectroscopic access to the areas of the SOC that are of interest. In particular, issues with sealing, temperature gradients, signal strength and cell configuration are discussed and final designs are presented. Preliminary results obtained during co-electrolysis operation are also presented.
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High temperature co-electrolysis of steam and carbon dioxide using a solid oxide cell (SOC) has been shown to be an efficient route to produce syngas (CO + H2), which can then be converted to synthetic fuel. Optimization of co-electrolysis requires detailed understanding of the complex reactions, transport processes and degradation mechanisms occurring in the SOC during operation. Currently, electrochemical measurements are conducted in-situ during electrolysis operation, however many analytical techniques are only used ex-situ, before and/or after electrolysis operation. In some cases the analytical techniques used are destructive (e.g. SEM imaging of the cell microstructure). In order to fully understand and characterize co-electrolysis in SOCs, in-situ monitoring of the reactants, products, and the cell itself are necessary.
As part of the UK-wide £5.7m 4CU project (A Comprehensive, Coordinated Programme for Carbon Capture and Utilisation Research) we are developing a suite of in-situ characterization techniques for high temperature SOC operation. In this paper we report the use of DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) to probe the reactions occurring during dry CO2 electrolysis and co-electrolysis.
The design and commissioning of the rig for in-situ characterization will be presented, along with a discussion on the challenges of spectroscopic access to the areas of interest of an SOC operating at high temperature. Infrared spectra showing CO adsorption on Ni-YSZ powdered catalyst and electrode surfaces will be presented.
A technique is described f> the preparation of beryl liu;;i foils by vapor deposition. The hitjh-purity, pinhoie-free foils are v.icimn tight and suitable for nany x-ray analysis applications. The beryllium is evaporated from an electron heai'i healed crucible source onto a heated substrate. Substrate temperatures of 4bO to 700°C are necessary to obtain the desired mechanical properties of thp foi!s. At these temperatures, contamination of the foils by diffusion of the substrate material into the beryllium can be a significant problem, as impurity levels of more than several hundred ppro arc detrimental to the x-ray transparency of the windows. This problem is minimized by careful selection and preparation cf the substrate. A clean deposition system and pure source naterial are necessary to preserve elemental integrity of the vapor-deposited foils.
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