Enhancing CO₂ Adsorption on MgO: Insights into Dopant Selection and Mechanistic Pathways

Inspired by our recent success in designing CO₂-phobic and CO₂-philic domains on nano-MgO for effective CO₂ adsorption, our ongoing efforts focus on incorporating dopants into pristine MgO to further enhance its CO₂ adsorption capabilities. However, a clear set of guidelines for dopant selection and a holistic understanding of the underlying mechanisms is still lacking. In our investigation, we combined first-principles calculations with experimental approaches to explore the crystal and electronic structural changes in MgO doped with high-valence elements (Al, C, Si, and Ti) and their interactions with CO₂. Our findings unveiled two distinct mechanisms for CO₂ capture: Ti-driven catalytic CO₂ decomposition and CO₂ polarization induced by Al, C, and Si. Ti doping induced outward Ti atom displacement and structural distortion, facilitating CO₂ dissociation, whereas C doping substantially bolstered the electron donation capacity and CO₂ adsorption energy. Pristine and C-doped MgO engaged CO₂ through surface O atoms, while Al-, Si-, and Ti-doped MgO predominantly relied on dopant-O atom interactions. Our comprehensive research, integrating computational modeling and experimental work supported by scanning electron microscopy and thermal gravimetric analysis, confirmed the superior CO₂ adsorption capabilities of C-doped MgO. This yielded profound insights into the mechanisms and principles that govern dopant selection and design.