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As the impacts of climate change continue to worsen, global demand for a reduction in greenhouse gas emissions will continue to grow. Tri-reforming of methane is a practical technique to neutralize CO₂ emissions directly from the stack with a desirable H₂/CO product ratio. The process synergistically utilizes dry reforming (DR), steam reforming (SR), and partial oxidation of methane (POM). Tri-reforming has been demonstrated to be feasible on an industrial scale at the Korean Gas Corporation (KOGAS) to produce dimethyl ether. One of the key advantages of tri-reforming is that it is thermodynamically favorable in comparison to DR. Typically, Ni-based catalysts are preferred for tri-reforming due to a relatively low cost and high activity. The activity of Ni catalysts can be improved by developing materials that demonstrate high resistance to oxidation and coke formation. This could be achieved by controlling the Ni particle size and enhancing the metal-support interaction. In this work, two unique catalysts, Ni-CeO₂ nanoparticle and NiO-CeO₂@SiO₂ coreshell, were synthesized to investigate the particle size effect on tri-reforming activity. Modification of particle size may provide control over the surface area of active site exposure. The results showed that core-shell structures had less deactivation and comparable activity. Particle size was modified by altering calcination temperature and metal ratios. Ni particle size has been shown to range between 13 and 52 nm on the synthesized catalysts. This particle size could be maintained after the reaction. The two-step calcination process used in the preparation of Ni-CeO₂ catalysts, in comparison to the one-step calcination process, does not enhance the tri-reforming activity due to a weak metal-support interaction. In the future, an investigation of similar materials that could include metals such as Zr, Ti, and Mg will be conducted. Additionally, the impact of NO_x and SO₂ on catalytic activity during a tri-reforming reaction will be investigated.