Catalytic activity of silicene biflakes for CO₂ reduction: a theoretical approach

The use of renewable energy sources to reduce carbon dioxide (CO₂) emissions has gained significant attention in recent years. The catalytic reduction of CO₂ into value-added products is a promising approach to achieve this goal, and silicene biflakes (2Si) have been identified as potential candidates for this task. In this study, we explored the catalytic activity of these structures using density functional theory calculations. Our results show that the reaction pathway involves the adsorption of CO₂ onto the silicene surface, followed by the addition of hydrogen molecules to form products such as formic acid, methanol, methane, carbon monoxide, and formaldehyde. Our proposed mechanism indicates that silicene biflakes exhibit a higher affinity for CO₂ than single-layer silicon. We also found that the hydrogenation with H₂ occurs by adding one hydrogen atom to the absorbed CO₂ and another to the surface of 2Si. Intermediate species are reduced by systematically adding hydrogen atoms and removing water molecules, forming formic acid as the most probable product. The rate-controlling step for this reaction has an energy of 32.9 kcal mol^-1. In contrast, the process without a catalyst shows an energy of 74.6 kcal mol^-1, suggesting that the silicon bilayer is a structure with outstanding potential to capture and reduce CO₂. Our study provides important insights into the fundamental mechanisms underlying the silicene-mediated CO₂ reduction and could facilitate the development of more efficient catalysts for this process.