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Oxidative Chemical Vapor Deposition of Conjugated Polymers: Electroactive Organic Thin Films
The combination of wind, solar, and electrochemical devices (e.g., batteries and supercapacitors) are cost-competitive alternatives to fossil fuel sources. To justify the use of electrochemical devices, we need to enhance the kinetics of the reactions involved in electrochemical devices by employing catalysts. The high cost of platinum group catalysts, as the traditional choice of catalysts, and the relatively high amount of needed material make the catalyst the primary barrier to large-scale employment of electrochemical devices. Thus, the development of cheap, abundant, and effective catalysts is an essential step toward the advancement of green energy conversion and storage technologies. In this thesis, we have been focused on investigating Conjugated polymers (CPs) for their electrocatalytic applications. We use a vacuum-based method, oxidative chemical vapor deposition (oCVD), to synthesize, coat, and dope thin films of CPs in a single step. Here, we expanded the use of oCVD to polymerize 3,4-ethylenedioxythiophene (EDOT) using antimony pentachloride and vanadium oxytrichloride as novel oxidants. We investigated the catalytic activity of the oCVD-PEDOT films toward oxygen reduction reaction (ORR) and their applications as air cathodes. As-deposited oCVD-PEDOT thin films catalyzed ORR with the onset of 0.74 vs RHE. For the first time, we also synthesized poly(3,4-ethylenedithiathiophene) (PEDTT) thin films in the oCVD reactor. PEDTT revealed bifunctional electrocatalytic activity toward ORR, and oxygen evolution reaction (OER), with catalysis onsets of 0.87 and 1.72 vs RHE, respectively. Furthermore, we studied the effect of dopants on the electrocatalytic activity of oCVD-poly(selenophene) thin films toward ORR. The results revealed that dopant exchange of the oCVD-poly(selenophene), either chemically or electrochemically, significantly enhances the catalytic activity of the material. Finally, we developed a novel technique based on nanoconfinement of the substrates to induce the heterogeneous nucleation and growth of highly crystalline polymeric thin films. The synthesized crystalline CPs are uniaxially oriented toward the (00l) direction that is not observed previously. Highly crystalline CPs showed enhanced charge storage properties up to 96% compared to the amorphous counterpart.
Chemical engineering|Molecular chemistry|Electromagnetics|Polymer chemistry|Climate Change
Kaviani, Shayan, "Oxidative Chemical Vapor Deposition of Conjugated Polymers: Electroactive Organic Thin Films" (2021). ETD collection for University of Nebraska - Lincoln. AAI28645090.