Formation of 3D graphene-Ni foam heterostructures with improved performance and durability for bipolar plates in a polymer electrolyte membrane fuel cell

Abstract

Improving the lifetime and the operational stability of polymer electrolyte membrane fuel cells (PEMFCs) is critical for realizing their implementation as a highly-efficient energy conversion system. However, the chemical instability of metal bipolar plates in the destructive operating environment inside PEMFCs leads to decreased performance and durability. Therefore, rational interface passivation techniques are critical for further boosting the development of PEMFCs. In this work, we report a novel method for coating highly-crystalline multilayer graphene (Gr) as a superficial protective layer (thickness of ~12 nm) onto 6 x 6 cm2 Ni foam within short periods (t≤5 min) via the facile and rapid thermal annealing (RTA) of poly(methylmethacrylate) as a solid-state C source. The synthesized graphene layers have a low defect density and completely cover the 3D-structured surface of the Ni foam, dramatically enhancing its corrosion resistance, interfacial contact resistance(ICR), and hydrophobicity. Electrochemical analysis revealed that the 3D Gr-coated Ni foam outperforms bare Ni foam and amorphous-C-coated Ni foam by providing a two-order-of-magnitude lower corrosion rate in the operational environment for a PEMFC. After stability tests in aggressive environments, the 3D Gr-coated Ni foam retained its outstanding ICR of 9.3 mΩ∙cm2 at 10.1 kgf∙cm-2. A H2/air PEMFC fabricated using the Gr-coated Ni foam as bipolar plates showed a substantially enhanced maximum power density of ~967 mW∙cm-2, which is the best among the reported metal foam bipolar plates. This study demonstrates that 3D Gr-coated Ni foam prepared using our proposed new coating method exhibits superior characteristics as an inhibitor for high-efficiency performance of a PEMFC with durability. Our facile coating approach can pave the way to further enhance energy conversion systems through interface engineering.