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WEB Functionalized Oxygenated Materials to Study Effects of Interfaces for Energy Conversion Devices

Wednesday (23.09.2020)
17:20 - 17:35 Z: Special Symposia I
Part of:

The study of energy conversion devices such as unitized regenerative fuel cells (URFC) is necessary for both space exploration missions and renewable energy concerns. To optimize such devices, use of functionalization is necessary when using materials such as transition metal oxides (TMOs) and multidimension carbon structures (MCSs). However, when doing so, choosing the correct combination of TMOs, MCSs, and their functional oxygen groups (FOGs) can prove to be very difficult as little research has been done [1,2]. To better understand and encompass the enormity of the problem, representative catalysts within the field were utilize in several variations: graphene oxide (GO), metal-organic frameworks (MOFs), several TMOs (ZrO2-x, TiO2-x, & CeO2-x), and FOGs (epoxy, hydroxyl, carboxyl, & phosphate). MCSs are used to leverage their large surface area and excellent electronic conductivity. However, for GO, oxygen-based FOGs exist on edges and wrinkles while the basal plane stays relatively non-reactive to provide adsorption for nanoparticles [3]. To catalytically activate the basal sites for adsorption between TMOs and GO, the use of phosphoric, hydrobromic and/or oxalic acids were used. These were reacted with metal precursors (Ce(NO3)3 or ZrOCl2) or nanoparticles (P25) or nanoparticles using the hydrothermal method. For MOF structures, due their susceptibility towards degradation after the common step of pyrolysis, a thin film of TMOs are used. However, to adhere the TMOs properly onto the MOF, we leverage acid treatment similar to our treatment of GO. The hydroxylated CeO2/GO hybrids showed the best performance in typical electrochemical electrolyte. Using both material/experimental analyses, a strong adsorption of TMOs GO’s basal plane prohibited restacking and that, the particle-carbon interfaces (as oppose to the particle or GO itself) dictates the performance and reaction route as indicated in density functional theory calculations. In addition, a hybrid catalyst where TiO2 nanodots are uniformly adsorbed on phosphorylated MOF by atomic layer deposition (ALD) showed better performance when compared the aforementioned CeO2/GO hybrid. Materials characterization emphasizes a strong adhesion of TMOs upon MOF structures, thus providing ample surface interactions for favorable reaction route is important. Therefore, activation of catalytic sites can be realized by a proper engineering of interfaces in each hybrid systems.

Simranjit Grewal
University of California