Balancing Corrosion Resistance and Electronic Conductivity in Nanoscale Amorphous Carbon Layers via Oxidizing Engineering

A commercially available amorphous carbon (a-C)-coated bipolar plate (BP) faces critical challenges of mitigating the rapid deterioration of electronic conductivity resulting from the corrosion at high potential in proton-exchange membrane fuel cells (PEMFCs). This work proposes then verifies that creating an oxidized a-C layer on C/Ti coating is able to mitigate corrosion while reserving available conductivity. Controllable oxygen incorporation in the a-C layer effectively lowers the adsorption energy of corrosive ions. Meanwhile, owing to a downward shift of the valence band maximum (VBM), the coating achieves a positive transpassivation potential of 1.36 V and mitigates continuous dissolution. Particularly, as a benefit from controllable oxidation states (∼30%) and the electron tunneling effect through nanoscale oxide layer (∼15 nm), this coating reserves a considerable conductivity, which remarkably outperforms those of BPs with conventional a-C coatings. This work highlights the importance of oxidation states of the a-C layer on BPs to achieve balanced corrosion resistance and conductivity.