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Dong, Yan

University of British Columbia

Defect engineering is a promising strategy for tailoring the electronic structure and charge distribution of catalysts, which could achieve unexpected physical and chemical properties to enhance the catalytic activity and durability. Recently, defect engineering is widely used in the design of carbon-based catalysts for electrochemical reactions. However, most of the research involving carbon defects relates to the heteroatom defects. The concept of topological carbon defects has been proposed and investigated in oxygen reduction reaction (ORR), but the exploration of topological carbon defects is still in its infancy. The design of carbon materials with high density homogeneous topological carbon defects and their extended application in other key electrochemical reactions are still big challenges. In this thesis, an efficient NH3 thermal treatment strategy is proposed for thoroughly removing pyrrolic N and pyridinic N dopants from N-enriched porous carbon particles, to create high-density topological carbon defects in carbon frameworks. The as-prepared 3-dimensional topological defected porous carbon (DPC) particles are investigated by near-edge X-ray absorption fine structure measurements and local density of states analysis, and the defect formation mechanism is revealed by reactive molecular dynamics simulations. The resultant DPC is used as an electrocatalyst in electrochemical carbon dioxide reduction (ECR), yielding a superficial current density of -2.8 mA cm⁻² (-28 A m⁻²) with Faradaic efficiency of 95% for CO generation at 25 °C and 101 kPa in 0.1 M KHCO₃ aqueous solution. The role of the topological carbon defects is analyzed in ECR. Then the carbon-based material enriched with topological defects is selected to serve as a substrate material to investigate the heterojunction effect of Pt and topological carbon defects. Both experimental characterizations and theoretical simulations reveal that the strong Pt-defect interaction can modify the electronic structure and charge distribution on the interface of the catalyst. Different Pt-defect coupling catalysts are prepared and the influence of the topological carbon defects on Pt are analyzed. Pt supported on DPC (Pt-DPC) catalyst achieves a 55 mV positive shift of half-wave potential for ORR in O2 saturated 0.1 M HClO4 electrolyte compared with commercial Pt catalyst on graphitized carbon at 25 °C and 101 kPa.

Text; Still Image

2022-09-06

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/82667

Chemical and Biological Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/