Enhancing CO2 reduction through the catalytic effect of a novel silicon haeckelite-inspired 2D material.

We propose a novel 2D material based on silicon haeckelite (Hck), whose structure contains a silicon atom arranged in a periodic pattern of pentagons and heptagons. Stacking the two layers gives rise to a planar geometry of the layers that compose it. This new structure presents a semiconductor character with a band gap of 0.17 eV. Furthermore, we studied CO2 reduction using molecular hydrogen to form formic acid, carbon monoxide, formaldehyde, methanol, and methane. All these have been studied theoretically at the Grimme D3BJ corrected TPSS/def2-SVP level. A massive biflake containing 132 Si atoms was used to model the Hck surface. According to the results, CO2 capture with Hck is a spontaneous step; in contrast, the same process for silicene mono- and bi-flakes studied previously was endergonic. After the capture of CO2, the addition of H2 to the substrate passes through an intermediate containing a Si-H bond. The formation of Si-H intermediates is the origin of the catalytic effect, facilitating H2 dissociation and acting as the hydrogen atom donor for the substrate. These intermediates are transformed by adding hydrogen atoms and losing water molecules, producing formic acid and formaldehyde as the most probable products, with rate-controlling steps of 29.2 and 27 kcal mol-1, whose values were less than those exhibited by the silicene biflake. This means that the silicon haeckelite biflake presents better catalytic activity than the silicene biflake. The results show that the novel 2D silicon hackelite material has remarkable potential for CO2 capture and reduction. The theoretical analysis of this innovative 2D structure provides valuable insights into the potential applications of silicene-based materials.

The bifunctional catalytic role of water clusters in the formation of acid rain.

State-of-the-art chemical bonding analyses show that water clusters have a bifunctional catalytic role in the formation of H2SO4 in acid rain. The embedded H2O monomers mitigate the change in the chemical bonding scenario of the rate-limiting step, reducing thereby the corresponding activation energy in accordance with Hammond's postulate. We expect that the insights given herein will prove useful in the elucidation of the catalytic mechanisms of water in inorganic and organic aqueous chemistry.