Author ORCID Identifier

https://orcid.org/0009-0003-5128-5958

Semester

Summer

Date of Graduation

2026

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

Yuxin Wang

Committee Member

Wenyuan Li

Committee Member

David Graham

Committee Member

V'yacheslav Akkerman

Abstract

The catalytic hydrogenation of carbon dioxide (CO2) to methane represents a promising strategy for carbon utilization and renewable energy storage within power-to-gas systems. When coupled with hydrogen derived from renewable electricity, CO2 methanation enables the conversion of intermittent energy sources into storable and transportable chemical fuels compatible with existing natural gas infrastructure. Nickel-based catalysts have emerged as leading candidates for this reaction due to their high activity towards CO2 methanation, abundance, and cost. However, the performance and long-term stability of Ni catalysts are strongly influenced by catalyst support properties, Ni nanoparticle size, and promoter effect, and a fundamental understanding of these effects remains incomplete.

This dissertation develops a comprehensive structure–reactivity framework for CO2 methanation over Ni-based catalysts by systematically investigating the roles of catalyst support, Ni nanoparticle size, and promoter. A series of well-defined Ni nanoparticle catalysts supported on reducible oxides (CeO2 and TiO2), a non-reducible but active oxide (Al2O3), and inert support (SiO2) were synthesized using controlled preparation methods to achieve varied Ni nanoparticle sizes on different supports. Extensive characterization, including transmission electron microscopy, chemisorption, temperature-programmed techniques, and in situ infrared spectroscopy, was employed to correlate catalyst structure with CO2 methanation activity, stability, and suggested reaction pathways.

The results show that, on reducible supports (TiO2 and CeO2), CO2 methanation reactivity initially increases and then decreases with increasing Ni nanoparticle size. Meanwhile, on the non-reducible but active support (Al2O3), CO2 methanation reactivity increases with increasing Ni nanoparticle size within the range studied. In situ infrared spectroscopic analysis further demonstrates that the methanation pathways depend strongly on both Ni particle size and support identity. In addition, the promotional effects of the f-block element gadolinium were examined in Ni-based catalysts. Gd promotion increased methanation activity and stability by enhancing CO2 adsorption, improving reducibility, while suppressing strong CO adsorption that leads to deactivation in monometallic Ni systems.

Overall, this dissertation provides fundamental insights into how catalyst support properties, metal particle size, and promoter elements govern CO2 methanation performance. The structure–reactivity relationships established in this dissertation offer guiding principles for the design of efficient and stable Ni-based catalysts for carbon utilization and sustainable energy applications.

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