Enhanced corrosion resistance of LaBC film for bipolar plate coatings in proton exchange membrane fuel cells

LaB6 have been using as hot electron emission materials to serve as hollow cathode ions source, which can help to enhance forming densen films. Besides, La can easy oxide to form La2O3 which can hinder penetration of water to improve the anti-corrosion properties. Thus, we embed LaB6 in carbon which can be employed as sputtering target, expecting to hot the plasma to get more sp2 carbon involved in growth a-C films. As a result, the LaBC film show higher ID/IG values, which improves the graphitization of the carbon matrix, thus partially solving the contradiction between electrical conductivity and corrosion resistance of the LaBC film. The corrosion current density of the LaBC film coated SS316L reduced by one and two orders of magnitude compared to the a-C film coated and uncoated SS316L, respectively, which can be attributed to the formation of boron oxide and lanthanum oxide on the surface of the film. Boron oxide is a waxy substance, and under the dual obstruction of boron oxide and lanthanide oxide, the corrosive solution is difficult to penetrate into the surface and reach the substrate, which greatly delays the oxidation and corrosion of the substrate. Therefore, the LaBC film are expected to be effective bipolar plate coatings for proton exchange membrane fuel cells.