Reactions between HOCO⁺ and H₂ Produce Water: a Computational Study^†

Controversies and arguments about the origin of planetary water have aroused enthusiasm to search for possible chemical sources. Considering the CO₂-rich atmospheres of Mars, Venus, and the prebiotic Earth, we propose that chemical reactions between HOCO⁺ and H₂ can contribute to the production of H₂O on the basis of high-level calculations. As for the reagents, HOCO⁺ can form via the protonation of CO₂, while H⁺ and H₂ are from the solar wind or interstellar space. Note that one of the reaction pathways undergoes multiple transition-state complexes and exhibits the roaming-like dynamics feature. Moreover, intermolecular proton or hydrogen transfer is a key step in the production of H₂O, thereby H-tunneling effect profoundly enhances the reaction rate in a wide range of temperatures or collision energies.