Laser-based production of reduced graphene oxide coatings on metallic bipolar plates for improved corrosion resistance and interfacial contract resistance in PEM-FC

The corrosion-induced degradation of metallic bipolar plates (BPP)in proton exchange membrane fuel cells (PEM-FC) leads to increased interfacial contact resistance (ICR, R_IC, R_BPP/GDL), limiting the fuel cell stacks efficiency and lifetime. Conventionally, thin (precious) metal coatings are applied via vacuum-based processes to mitigate these issues, but these methods are costly and energy-intensive. The research presented in this work evaluates a new, highly inline-capable, laser-based approach for the generation of corrosion resistant reduced graphene oxide (rGO) coatings on metallic bipolar plates, in ambient conditions. Graphene oxide (GO) thin films, deposited by ultrasonic spray coating on AISI 316 L stainless steel, are reduced to conductive, corrosion resistant rGO layers utilizing nanosecond-pulsed fiber laser radiation (λ = 1064 nm) The study investigates the influence of different laser processing parameters (average laser power P_avg, track spacing d_y and pulse repetition frequency f_rep) on the reduction process. Structural and compositional transformation of GO to rGO during thermal and laser-induced reduction are analyzed via optical microscopy, UV-Vis-NIR spectroscopy, and X-ray diffraction (XRD). The electrical and electrochemical properties of GO and rGO coatings were assessed through-plane and interfacial contact resistance analysis and potentiodynamic polarization experiments. The results indicate that the laser reduction of GO is an effective method for the generation of rGO thin films. The transition between GO and rGO was successfully observed in UV-Vis-NIR spectroscopy and XRD and a processing window (X- and Y-dimension 25 x 25 mm², d_y 0.03 mm, P_avg 3.8 W, V_scan 800 mm/s, f_rep 950 kHz) was established. An interfacial contact resistance of rGO to a gas diffusion layer was determined to 3.25 mΩcm², meeting the U.S. Department of Energy 2025 technology targets (⪅10 mΩcm² at 140 N/cm²). Electrochemical corrosion analysis shows that rGO-coated AISI 316 L possess I_corr of 0.246 μA/cm² and E_corr of 0.63 V vs. RHE, exhibiting improved stability compared to uncoated steel samples and performance comparable to gold-coated AISI 316 L. The work demonstrates a scalable and energy-efficient method to produce GO-based BPP coatings offering promising properties. Further studies are planned to investigate the effects of laser processing on the coating properties in depth.