Graphene-Dominated Hybrid Coatings with Highly Compacted Structure on Stainless Steel Bipolar Plates

Highly conductive corrosion protection coatings are necessary
for
metallic bipolar plates (BPs) of the proton-exchange membrane fuel
cell. Graphene coatings have the potential of protecting metal substrates
from corrosion without obscuring their excellent electrical conductivity.
The electron transfer in the coatings facilitates the formation of
galvanic cells, so the challenge is to block the mass transfer of
the corrosion process. Here, we constructed highly compacted hybrid
coatings with aligned water-dispersible graphene layers. The water-dispersible
graphene (SG) held an electrical conductivity of >270 S cm–1 while providing an unprecedented dispersibility,
which can be redispersed
from filter cake with a concentration of 120 mg mL–1 or even dry state. The cohesion of the hybrid coatings was attributed
to the interaction between highly aligned SG layers and the heterointerface
between SG and polydopamine (PDA), as proven by the molecular dynamics
simulations. The hybrid coatings presented a corrosion current density
of 0.023 μA cm–2 and an interfacial contact
resistance of 9.94 mΩ cm2, which meets the requirements
of corrosion protection and electron transfer for the coatings on
metallic BPs. The water-based fabrication method of the graphene-dominated
hybrid coatings was a promising alternative of the vacuum-based deposition
method for industrial production.

质子交换膜燃料电池（proton-exchange membrane fuel cell）的金属双极板（BPs）亟需兼具高导电性与防腐性能的涂层。石墨烯涂层可在不损害金属基底优异导电性能的前提下，对其实现防腐保护。涂层内的电子转移会促进原电池的形成，因此阻断腐蚀过程中的传质过程成为核心挑战。本研究构建了具有定向排列水分散性石墨烯（water-dispersible graphene，SG）层的高致密复合涂层。该水分散性石墨烯的电导率大于270 S cm⁻¹，同时具备前所未有的分散性能：可从浓度为120 mg mL⁻¹的滤饼中重新分散，甚至可在干燥状态下实现再分散。复合涂层的内聚性源于高度定向排列的SG层之间的相互作用，以及SG与聚多巴胺（PDA）之间的异质界面作用，该结论已通过分子动力学模拟得到验证。该复合涂层的腐蚀电流密度为0.023 μA cm⁻²，界面接触电阻为9.94 mΩ cm²，可满足金属双极板涂层的防腐与电子传输需求。这种以石墨烯为主体的水基复合涂层制备方法，有望成为工业生产中替代真空沉积法的极具潜力的备选方案。