Electrical and thermal transport properties of vanadium oxide thin films on metallic bipolar plates for fuel cell applications

We have focused on the in-depth comparative evaluation of the suitability of electrically-induced thermal transport characteristics of highly disordered vanadium oxide thin films deposited onto metallic bipolar plates as an expeditious self-heating source for the successful cold-start of fuel cells in a subfreezing environment. To achieve this, sol-gel derived vanadium oxide thin films on the non-polished surface of 316L austenitic and 446M ferritic substrates have been fabricated by a dip-coating process. The effects of electrical properties on thermal energy dissipation rate of the as-synthesized thin films deposited onto 316L and 446M stainless steel plates were firstly investigated and compared with each other. Subsequently, a series of physical, chemical, and structural analyses of the thin films have been performed using several analytical techniques such as the ASTM D3359, the ASTM D5946, XPS, and FE-SEM. The most important finding of this study was that the electrical resistivity of the thin films on 446M ferritic substrate was extremely low on a level of 4.8% of the 316L sample at −20 °C, and then the surface temperature rise of the thin film on 316L austenitic substrates was approximately 21.8 times greater than that of 446M ferritic substrates under simulated cold starting conditions (i.e., at a current density of 0.1 A·cm−2 at −20 °C). Therefore, we concluded that vanadium oxide thin films on 316L austenitic stainless steel plates appears to be more applicable than those of 446M ferritic substrates for the cold-start enhancement of fuel cells from the practical point of view.