Low InterfacialContact Resistance between Carbon-BasedGas Diffusion Layer and Sputter-Deposited Anatase TiO2

Abstract

Abstract Reducing the interfacial contact resistance between separators and gas diffusion layers is critical for achieving high-power polymer-electrolyte membrane fuel cells. Stringent targets for contact resistance below 3.0 mΩ cm2 have been proposed; however, achieving such values using practical separator materials remains challenging. Here, we demonstrate that electrically conductive anatase Nb-doped TiO2 (TNO) thin films deposited onto stainless steel separators by RF magnetron sputtering exhibit a low contact resistance of 2.6 mΩ cm2 against carbon-based gas diffusion layers. Postdeposition vacuum annealing at 500 °C, suitable for practical stainless steel, reduces contact resistance. X-ray diffraction, electron backscattering diffraction, and Raman spectroscopy mapping reveal that a high carrier density (∼1021 cm–3) in Nb-doped TiO2 thin films plays a key role in reducing interfacial contact resistance. These findings highlight TNO as a promising inorganic coating material for next-generation high-power fuel cells.