Significant enhancement of corrosion resistance of stainless steel with nanostructured carbon coatings by substrate-catalytic CVD

Abstract

The bipolar plate is the major component of proton-exchange membrane fuel cells and also a critical contributor to the fuel cell performance. Metallic bipolar plate (MBP) has high impact resistance but its poor chemical stability limits the service lifetime and stack stability. One of the feasible methods to enhance the corrosion resistance of MBPs is the formation of conductive protective coatings on the MBP surface. In this work, nanostructured carbon coatings were deposited on stainless steel by chemical vapor deposition using the substrate itself as catalysts. Under the optimized conditions, the corrosion potential of carbon coatings with dense spherical structure on stainless steel (2.1 V RHE ) is much higher than that of uncoated one (1.2 V RHE ), and even greater than that of commercial graphite bipolar plates (1.7 V RHE ), showing 75% and 23.5% improvement in corrosion resistance, respectively. Moreover, the corrosion current density of stainless steel with dense sphere-assembled coatings decreases to 0.2 mA/cm 2 , which is two orders of magnitude lower than that of graphite bipolar plates (27.4 mA/ cm 2 ) at the same applied potential (2.2 V RHE ). The coated stainless steel with excellent anticorrosion properties has potential applications for MBPs in proton-exchange membrane fuel cells, electrochemical treatment of waste water, and current collectors in lithium-ion batteries.

Development of Microstructured Carbon Coatings by Substrate-Catalytic CVD

“…Similarly, Chen et al pointed out the formation of CµSs with diameters between 500 nm and 3 µm as a consequence of the high C 2 H 2 :H 2 ratio (using an AISI 304 SS as the substrate) [2]. On the other hand, Shu et al described that the formation of CµSs assemblies is due to the growth rate of the carbon layer, which exceeds the migration rate of metal atoms (from the substrate to the surface), which would otherwise catalyze the formation of filament [1]. However, while in the study mentioned above, the increase in temperature favors particle formation, in the present one, the increase in temperature hampers the formation of the CµSs.…”

“…Nanostructured carbon coatings for steel electrodes, due to their remarkable characteristics, such as high electrical conductivity, hydrophobicity, and chemical inertness, have found a place in many applications as proton-exchange membrane fuel cells [1], porous current collectors for lithium-ion batteries [2], and as an effective support to grow carbon nanotubes [3][4][5], vertically-oriented graphene [6], carbon fibers [5] and micro-sized carbon spheres [5]. However, the coating properties can vary widely due to the substrate composition and synthesis conditions, for example, different qualities of the carbon layer can both support or worsen the substrate corrosion resistance.…”