HTE, a highly promising method for producing hydrogen - Part4-

over 1 year ago

In the previous article, we discussed the problems caused by the materials used in the manufacture of interconnectors in the HTE electrolyzer, and how they would cause the cell to deteriorate. As a result, materials with specific properties must be used, the most important of which are: the capacity to resist high temperatures for an extended period of time, good electrical conductivity, no chromium poisoning, and resistance to oxidation. Some alloys have been proposed, most of them containing chromium, due to their corrosion and rust-resistant properties when formed with iron and nickel. But the problem is that this substance causes chromium poisoning. It was also explored that noble metals can be a great solution, but their cost is very high when we talk about industrial production.

In general, and with regard to all of the materials and alloys proposed in the previous article, researchers at The Atomic Energy and Alternative Energies Commission (CEA) believe that these solutions are relatively feasible for long-term operation of the electrolyzer HTE. As a result, the primary goal of their research was to investigate the feasibility of using chromium-free oxides in the fabrication of interconnectors in the electrolyzer HTE. The findings of a study on a mixed oxide of manganese and cobalt (CO, Mn)3O4 revealed that at 800 °C, this oxide has a conductivity a thousand times better than chromium oxide.

Researchers are also interested in other substances, such as lanthanum perovskites. Currently, ferritic stainless steel that has had cobalt vacuum-deposited onto it is available from metal alloy manufacturer Sandvik. Spinel-like oxides are created by high-temperature oxidation, which increase conductivity and lessen chromium evaporation.

Perovskite oxide thin film- Wikipedia- By Magnunor

The CEA researchers are working to improve the structure and properties of the layers of the metallic deposits of the cobalt-manganese mixture, by converting these deposits into spinel oxide, with the aim of using it as a coating. The researchers found that these deposits are sticky, thin and have a high density. The resistance of the alloy/deposit coupling to prolonged exposure to high temperature is being assessed. The ability to control the alloy-deposit reactivity using intermediary layers has already been made possible by these researches, which have also helped to identify the vacuum spraying track's limitations and prospective enhancements.

Application of a cordierite layer on substrate by vacuum plasma spraying (VPS)

In order to achieve the proper density during the procedures of depositing powder suspensions, the researchers focus on the regulation of crucial characteristics, such as viscosity or dry matter content. This is an alternative coating process option. Screen printing is used in this instance to create the coatings. It is a type of printing that involves depositing a suspension—a combination of powder, a solvent, and additives—through a screen to the surface to be coated.