Graphite electrodes have long been the leading choice for industrial electrochemical applications such as oxygen production, hydrogen production and carbon monoxide detection. For these applications, they are chosen due to high conductivity. As a result of their many advantages, graphite electrodes are much cheaper than alternative solutions.
Production of graphite electrodes begins with the graphitization process, where raw materials are extruded to a rod shape and baked without oxygen. The electrode's unique characteristics are due to the baking process. The rod will be machined into the shape and size desired after the baking process. This is an important step in the production of graphite electrodes as it must be done to ensure that the electrode has the required dimensions and thickness.
The graphite can be machined to suit a number of uses. Graphite electrodes are made to be used as electrodes or nozzles when casting metals. Graphite is also used to make semiconductor crystals, and for metallurgical purposes.
Electrodes are coated in various materials that enhance performance. Carbon black, nickel and silver are some of the most common coatings. These are applied to the surface of the electrode to improve corrosion resistance and reduce adhesion of the electrode to the workpiece. These substances also improve the reactivity and corrosion resistance of electrodes.
Graphite also makes a great choice in cases where a higher level of purity must be maintained. In contrast to stainless steel graphite, which is also a conductor material, does not require the presence of an oxide coating on electrodes. The graphite material is also not affected by the oxidation of dissolved oxygen.
For low-cost gas sensor applications, home-made edge type screen-printed electrodes can be produced using RTIL. These are up to 10 times cheaper than the platinum equivalents. The current-sensing behaviour of these SPGEs towards dissolved oxygen in RTIL solvents is explored and compared to that of commercially available carbon screen-printed electrodes (C-SPE) from the company DropSens.
In this paper, the results of LTCA experimentation at varying levels of oxygen ([C2mim][NTf2] & [C4mim][PF6]) on SPGE and C SPE are described, with calibration charts, LODs & R2 values. These SPGEs and C-SPEs are also evaluated for their stability at high oxygen concentrations. The stability tests show that IEM scans with smaller areas and slower scan rates reduce the decline in current due to graphite-corrosion products. However, larger scan zones and faster scan speeds decrease ECE to get the same amount of current. Results of long-term constant-state analysis confirms this. These results show that low-cost graphite CEs are suitable for oxygen detection within RTILs, with performance acceptable at upper limits of permissible range.
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