Fuel cells are an alternative source of energy. Electricity in fuel cells is generated directly from chemical reactions – for example, by combining oxygen and hydrogen to form water. The main element of such fuel cells is a bipolar plate. It separates the substances, passes the ions, removes heat and by-products. Therefore, its quality determines the reliability of the entire element. Most often, the plate is made of graphite due to its thermal and chemical resistance. However, the production of such plates is expensive, and graphite is not strong enough from the mechanical viewpoint. RUDN professor and his colleagues from Bulgaria, Iran, and the UK has proposed a novel methodology to make bipolar plates from steel with TiN and CrN coatings - so they become stronger and cheaper.
"Bipolar plates are the most crucial component of fuel cells. The performance and lifetime of such fuel cells is determined mainly by two factors - corrosion resistance and interphase contact resistance of metal bipolar plates. To ensure these properties, a thin hard film from a conductive coating is applied to the plate," said Reza Kashy Zadeh Kazem, Professor, Department of Transport, RUDN University.
For the metal bipolar plate, the researchers chose a stainless steel alloy AISI410. The authors were faced with the task of choosing the best coating of the steel plate, which would make it sufficiently resistant to corrosion and interfacial contact. Scientists tested two possible options - a coating of titanium nitride and chromium nitride.
It turned out that both titanium nitride and chromium nitride improve the corrosion resistance of steel. However, chromium nitride performs better, it reduces the corrosion rate three times - up to 0.032 milli inches per year, while in pure steel this parameter is 0.096.
"Stainless steel coated with chromium nitride can be an excellent candidate for use in fuel cells as a bipolar plate due to its corrosion resistance, low cost of materials, and ease of manufacture," said Reza Kashy Zadeh Kazem, Professor, Department of Transport, RUDN University.