Faculty Advisor or Committee Member
N. Aaron Deskins, Advisor
Faculty Advisor or Committee Member
Michael M. Timko, Committee Member
Faculty Advisor or Committee Member
Ravindra Datta, Committee Member
Faculty Advisor or Committee Member
George Kaminski, Committee Member
Identifier
etd-061518-162659
Abstract
Record high CO2 emissions in the atmosphere and the need to find alternative energy sources to fossil fuels are major global challenges. Conversion of CO2 into useful fuels like methanol and methane can in principle tackle both these environment and energy concerns. One of the routes to convert CO2 into useful fuels is by using supported metal catalyst. Specifically, metal atoms or clusters (few atoms large in size) supported on oxide materials are promising catalysts. Experiments have successfully converted CO2 to products like methanol, using TiO2 supported Cu atoms or clusters. How this catalyst works and how CO2 conversion could be improved is an area of much research. We used a quantum mechanical tool called density functional theory (DFT) to obtain atomic and electronic level insights in the CO2 reduction processes on TiO2 supported metal atoms and clusters.
We modeled small Cu clusters on TiO2 surface, which are experimentally synthesizable. Our results show that the interfacial sites in TiO2 supported Cu are able to activate CO2 into a bent configuration that can be further reduced. The Cu dimer was found to be the most reactive for CO2 activation but were unstable catalysts. Following Cu, we also identified other potential metal atoms that can activate CO2. Compared to expensive and rare elements like Pt, Au, and Ir, we found several early and mid transition metals to be potentially active catalysts for CO2 reduction. Because the supported metal atom or cluster is a reactive catalyst, under reaction conditions they tend to undergo aggregation and/or oxidation to form larger less active catalysts. We chose Co, Ni, and Cu group elements to study their catalyst stability under oxidizing reaction conditions. Based on the thermodynamics of Cu oxidation and kinetics of O2 dissociation, we found that TiO2 supported Cu atom or a larger Cu tetramer cluster were the likely species observed in experiments. Our work provides valuable atomic-level insights into improving the CO2 reduction activities and predicts potential catalysts for CO2 reduction to valuable fuels.
Publisher
Worcester Polytechnic Institute
Degree Name
PhD
Department
Chemical Engineering
Project Type
Dissertation
Date Accepted
2018-06-13
Copyright Statement
All authors have granted to WPI a nonexclusive royalty-free license to distribute copies of the work, subject to other agreements. Copyright is held by the author or authors, with all rights reserved, unless otherwise noted.
Accessibility
Unrestricted
Repository Citation
Iyemperumal, S. (2018). Conversion of Carbon Dioxide to Fuels using Dispersed Atomic-Size Catalysts. Retrieved from https://digitalcommons.wpi.edu/etd-dissertations/505
Subjects
atomic-size catalysts supported catalyst density functional theory Modeling reaction conditions supported cluster stability CO2 reduction