Date of Award
Open Access Dissertation
John R. Monnier
In heterogeneous catalysis, it is a proven factor that the surface-specific activity and the catalyst selectivity strongly depends on the active sites which are determined by the composition, size, and shape of the particle. For structure-sensitive reactions favored by specific surface sites, such as corners, steps, or edges, TOF and selectivity can be greatly changed by the size of catalyst particles since the active site distribution will change with the size of the catalysts. Usually, metal particles are synthesized by two methods in industry, namely precipitation and impregnation, which often exhibit a broad size distribution. The grand challenge of colloidal chemistry, on the other side, is that the surfactants need to be thermally removed without losing original particle size distribution. Therefore, a precise composition and size control catalyst synthesis method needs to be developed to get a catalyst that have high activity and selectivity towards the desired product.
In this thesis, we therefore studied the electroless deposition (ED) in metal particles synthesis with precise control on the catalyst particle size and composition. Firstly, continuous ED is introduced to grow Pt particle on carbon support, and Pt particle average size and size distribution was found to be a function of the deposition time. Alumina supported silver (Ag) particles with different size are then generated using percolating ED bed by varying the deposition time. The catalyst performance on ethylene epoxidation under real conditions shows that the rate of ethylene oxide formation is a function of Ag particle size and the selectivity increases with Ag size. Lastly, the composition of the particles is tuned by depositing two or more metals through the ED method. In this case, a Pt-Ru bimetallic catalysts are prepared on oxygen groups functionalized carbon nanotubes support and its electro-catalytic activity toward methanol oxidation have been studied. Cyclic voltammetry (CV) testing shows that the ED driven Pt-Ru catalysts with strong Pt-support interaction have higher mass activities than the commercial Pt-Ru catalysts in the direct methanol fuel cells (DMFC). Moreover, co-ED is developed to co-deposit Cu and Pd and Ag plasmon with controlled composition, and the catalyst performance have been tested on the CO2 reduction reactions.
Based on the work in this thesis, we demonstrate that the ED method we proposed can be readily used in precise size and composition control metal catalyst synthesis at industry scale.
Xiong, W.(2021). Preparation, Characterization and Evaluation of Rationally Designed Catalysts by Electroless Deposition. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/6865