Vertical‐Graphene‐Reinforced Titanium Alloy Bipolar Plates in Fuel Cells

Abstract

membrane electrode assembly, collecting current, transporting gas reactants, and enabling thermal and water management. [2] In terms of these functions, a good BP material is required to possess the characteristics of reliable mechanical strength, high electrical and thermal conductivities, low gas permeability, good hydrophobicity, etc. Traditional graphite BPs are hindered from the mass production and long-term use by their brittleness and large gas permeability. [3,4] In contrast, metallic BPs, such as stainless steel, aluminum, titanium (Ti), and their alloys, can satisfy the requirements nicely, making them the attractive BP material candidates for PEMFCs. [5] Among these metals, Ti and its alloys have received widespread attention in recent years owing to their high specific strength and anticorrosion performance. [6] However, there remain two major challenges for the practical application of Ti and its alloys: i) their surfaces are naturally covered with a nonconductive passivation layer, which hampers the power density of PEMFCs due to the interface contact resistance (ICR) between BP and gas diffusion layer (GDL); ii) although the passive oxide layer benefits the anticorrosion performance of Ti and its alloys, corrosion will inevitably occur in the acidic operating environment of PEMFCs, leading to the degradation of PEMFCs' performance. [6,7] The bipolar plate (BP) serves as one of the crucial components in proton exchange membrane fuel cells (PEMFCs). Among BP materials, metallic BPs are widely employed due to their outstanding comprehensive properties. However, the interfacial contact resistance (ICR) between BP and gas diffusion layer together with corrosion of metallic BP under acidic operating conditions degrades the performance and stability of PEMFCs. Herein, an approach is proposed for the surface reinforcement of titanium (Ti) alloy BPs, relying on a directly grown vertical graphene (VG) coating via the plasma-enhanced chemical vapor deposition method. Compared with bare Ti alloy, the corrosion rate of VG-coated Ti alloy reduces by 1-2 orders of magnitude in the simulated PEMFC operating environments and ICR decreases by ≈100 times, while its thermal conductivity improves by ≈20% and water contact angle increases by 68.1°. The results can be interpreted that the unique structure of VG enables excellent electrical and thermal conduction in PEMFCs, and the highly hydrophobic VG coating suppresses the penetration of corrosive liquid as well as contributing to water management. This study opens a new opportunity to reinforce metallic surfaces by the robust and versatile VG coating for highperformance electrodes used in energy and catalyst applications.

Bush‐Shaped Vertical Graphene/Nichrome Wire for Blackbody‐Like Radiative Heating

“…PECVD has emerged as a significant approach for synthesizing graphene at a low temperature by coupling the energy of a plasma generator to boost the dissociation of precursors. [24][25][26][27] Here, the plasma was ignited using CH 4 as the carbon source at a radio frequency (RF) power of 150 W, leading to the growth of graphene on the Ni-Cr wire (Figure 1a). After the PECVD process, BVG/Ni-Cr wire turned quite black in contrast to the silver-gray surface of bare Ni-Cr wire (Figure 1b), which suggests the enhanced absorption in the visible wavelength.…”

Direct-Chemical Vapor Deposition-Enabled Graphene for Emerging Energy Storage: Versatility, Essentiality, and Possibility

“…The main bottleneck of industrial Al current collector lies in the local anodic corrosions during long-term electrochemical operation in organic electrolyte, which substantially impedes the achievement of long-lifespan and high-voltage rechargeable batteries. 60 Benefiting from the PECVD-enabled graphene coating, GA current collector is in favor of mitigating anodic corrosion and sustaining durable operation. As for anticorrosion performance evaluation, half cells using lithium foil as the anode and GA or pure Al foil (PA) as the cathode were subject to the cyclic voltammetry (CV) measurement.…”

Improvement in Corrosion Resistance and Interfacial Contact Resistance Properties of 316L Stainless Steel by Coating with Cr, Ti Co-Doped Amorphous Carbon Films in the Environment of the PEMFCs

“…Significant attention has been devoted to developing suitable coatings to improve corrosion resistance and ICR by mitigating these problems. Some surface engineering techniques exist for applying coatings, including chemical vapor deposition, magnetron sputtering, and electroplating [ 12 , 13 , 14 ]. Among the choices, magnetron sputtering is a desirable method for manufacturing various films on stainless steel.…”