Influence of surface roughness and hydrophobicity of bipolar plates on PEM performance

• Published in: Surface & coatings technology 2020-05, Vol.389, p.125676, Article 125676
• Main Authors: Madadi, F., Rezaeian, A., Edris, H., Zhiani, M.
• Format: Article
• Language: English
• Subjects: Aluminum; Atomic force microscopy; Coatings; Contact angle; Flooding; Fuel cell performance; HVOF; Hydrophobic coating; Hydrophobicity; Nuclear fuels; Plates; Profilometers; Protective coatings; Proton exchange membrane fuel cells; Relative humidity; Sprayed coatings; Substrates; Surface roughness; Surface roughness effects; Topology; Wettability
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2020.125676

The effect of surface roughness on wettability of different coating materials on bipolar plates employed in proton exchange membrane fuel cells (PEMFC) was investigated in this study. Aluminum substrate was coated with three different materials (NiCr, NiCrBSi, and Co(Ni)CrAlY) using high velocity oxy fuel (HVOF) process. Surface topology and roughness were then evaluated using atomic force microscopy and roughness profilometer. Moreover, the contact angle (CA) of different coatings was measured both in as-sprayed condition and after grinding in order to investigate the influence of roughness on the surface hydrophobicity parameter. It was found that among the three coatings with hydrophobic nature, NiCrBSi and Co(Ni)CrAlY showed the highest (128°) and the lowest (106°) CAs, respectively, whereas the CA of the uncoated Aluminum was determined to be 84° showing the hydrophilic nature of the substrate. The surface roughness of NiCrBSi, Co(Ni)CrAlY and NiCr were Ra = 7.632 μm, Ra = 5.510 μm and Ra =5.974, respectively. It shows that NiCrBSi and Co(Ni)CrAlY exhibited the highest and lowest surface roughness. It was also found that for all coating materials, power-current curves of the single cells illustrated a rising trend in power with increasing relative humidity from 30% to 100%. Such behavior was found to be due to the hydrophobic property of the coated surfaces through the removal of the produced water. This in turn prevented water blocking and flooding known as fuel cell performance and durability weakness points.. Among the sprayed coating materials used in this study, NiCrBSi exhibited the highest hydrophobic property, and hence, the greatest cell performance. •Effect of surface hydrophobicity on PEMFC performance has been investigated.•Hydrophobicity property was improved by increasing surface roughness.•Water removing in PEMFC process is manageable by surface properties amendment.•Among coatings, NiCrBSi exhibited higher hydrophobic and greater performance.