Effect of cobalt ion contamination on proton conduction of ultrathin Nafion film. (21st September 2020)

• Record Type: Journal Article
• Authors: Han, Aidi; Fu, Cehuang; Yan, Xiaohui; Chen, Junren; Cheng, Xiaojing; Ke, Changchun; Hou, Junbo; Shen, Shuiyun; Zhang, Junliang
• Is Part Of: International journal of hydrogen energy. Volume 45:Number 46(2020)
• Page Start: 25276
• Page End: 25285
• Publication Date: 2020-09-21
• Subjects: PEMFC -- Cobalt contamination -- Proton conduction -- Ultrathin Nafion film -- Catalyst layer; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2020.06.205
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: With the wide use of platinum alloy electrocatalysts proton exchange membrane fuel cells, the dissolution of transition metal in the acid environment of catalyst layer becomes a major concern due to the decreased catalytic activity during long-term operation. Although great efforts have been done, few attention is paid to the effect of transition metal ion contamination of Nafion ionomer that wrapped around catalyst particles within catalyst layer which might greatly influence the proton conduction. To elucidate such effect, ultrathin Nafion film on SiO2 model substrate is prepared via self-assembly method to represent the ionomer in fuel-cell catalyst layers, and the ultrathin film with specific thickness is further equilibrated in Co(NO3 )2 /HNO3 solutions with different Co 2+ concentration to achieve different doping level. Conductivity measurements demonstrate that the non-precious metal contamination severely worsens proton conduction of Nafion ionomer, but it is always ignored before. In addition, when the occupation of H + in Nafion ionomer is less than 50%, the activation energy shows a sharp increase, indicating a possible change in proton conduction mechanism. Graphical abstract: Image 1 Highlights: 40 and 120 nm Nafion thin films with different cobalt doping levels are prepared. Effect of cobalt doping level on proton conduction of Nafion ionomer is tested. The increase of cobalt doping level seriously reduces the proton conductivity.