Optimization of titanium alloy bipolar plate performance in proton exchange membrane water electrolysis with Cr/W/diamond-like carbon coating

Abstract

The operating environment for bipolar plates in proton exchange membrane water electrolysis (PEMWE) systems is highly challenging, characterized by high electrical potential, acidic pH, and elevated temperatures. Bipolar plates must possess high corrosion resistance and electrical conductivity to ensure stable and efficient system perfomance. Therefore, surface coatings are essential to decelerate oxidation on the substrate surface, preventing a significant increase in interfacial contact resistance (ICR). This investigation applied a Cr/W/diamond-like carbon (DLC) coating to titanium alloy (Ti-6Al-4 V, also known as TC4) surfaces using magnetron sputtering. The multilayer coating system was designed to enhance electrical conductivity and corrosion resistance of the bipolar plate while ensuring good coating adhesion. At potentials of 1.2 V, 1.5 V, and 1.8 V, the current densities measured during potentiostatic polarization were 0.11 μA·cm^-2, 0.19 μA·cm^-2, and 0.4 μA·cm^-2, respectively, showing a significant reduction compared to the TC4 matrix and demonstrating long-term stability. The Cr/W/DLC-coated TC4 bipolar plates exhibited an ICR of 16.98 mΩ/cm² under a contact pressure of 1.4 MPa. These results suggest that the coating provides exceptional corrosion resistance under PEMWE operating conditions while retaining electrical conductivity.