Ph.D. Dissertation Defense Committee:

• Ph.D. Advisor: Prof. Cafer Yavuz
• Committee Chair: Prof. Shadi Fatayer
• External Examiner: Prof. Qiang XU
• Committee Member: Prof. Dana Alsulaiman
• Committee Member: Prof. Anqi Wang

Abstract

Designing efficient and stable catalysts for CO2 conversion and methane reforming remains a critical challenge for sustainable energy technologies. This thesis presents two complementary studies that elucidate how metal-metal and metal-support interactions govern catalytic pathways in the dry reforming of methane (DRM) and reverse water-gas shift (RWGS) reactions. In the first part, Ni-Mo catalysts for DRM were investigated, demonstrating that controlled NiMo alloy formation significantly enhances CH4 and CO2 activation, suppresses carbon deposition, and improves long-term catalytic stability. Systematic optimization of the Ni/Mo ratio, coupled with structural and spectroscopic analyses, revealed that Mo incorporation tunes the electronic environment of Ni, promotes oxygen mobility, and stabilizes active Ni-Mo ensembles under high-temperature reforming conditions. In the second part, NiAu bimetallic catalysts supported on facet-engineered MgO—cubic MgO (100) and hexagonal MgO (111)—were investigated to elucidate facet-dependent hydroxyl environments and metal–support interactions. Au addition significantly enhanced CO2 conversion on Ni/MgO (100) by promoting NiAu alloying, accelerating carbonate decomposition, and weakening Ni–CO back-donation, thereby favoring selective RWGS and suppressing methanation. In contrast, strong Au binding and stable OH species on MgO (111) hindered alloy formation and reduced activity, with improved performance observed only at elevated temperatures due to OH desorption and enhanced Ni dispersion. Overall, these results highlight the critical roles of promoter effects, facet engineering, and hydroxyl-mediated interactions in tailoring catalytic pathways for CO2 conversion.