Activation of CO₂ in Photoirradiated CO₂–H₂O Clusters: Direct Ab Initio Molecular Dynamics (MD) Study

Abstract

Carbon dioxide (CO2) is one of the stable and inactive molecules that contribute to greenhouse gases. The development of new reactions of CO2 activation, chemical fixation, and conversion is a very important issue. In this report, the reactions of CO2–H2O binary clusters were investigated using a direct ab initio molecular dynamics (AIMD) method to find a new reaction of CO2 activation. Clusters composed of carbon dioxide and water molecules, CO2(H2O) n (n = 2–5), were utilized as a model of the binary cluster. The reaction dynamics of [CO2(H2O) n ]+ following the ionization of parent neutral clusters were also investigated. Two electronic states of [CO2(H2O) n ]+ were examined for direct AIMD surfaces: CO2[(H2O) n ]+ (ground state) and (CO2)+(H2O) n (excited charge transfer (CT) state). After the ionization of the clusters, a proton-transfer (PT) reaction occurred within the (H2O) n + moiety at the ground state, whereas the reactive HCO3 radical was formed at the CT state for OH addition to CO2 +: CO2 +(H2O) n → HCO3 + H+(H2O) n−1. The mechanisms of the PT process and the HCO3 radical formation were discussed based on the theoretical results.

Formation of Hydrogen Peroxide from O–(H2O)n Clusters

“…The total energy drift in all trajectory calculations was less than 0.01 kcal/mol. Direct AIMD calculations were carried out using our own code. − Similar calculations were carried out for O­( 3 P)­(H 2 O) n and O­( 1 D)­(H 2 O) n .…”

Proton Transfer vs Complex Formation Channels in Ionized Formic Acid Dimer: A Direct Ab Initio Molecular Dynamics Study

“…The total energy drifts in all trajectory calculations were less than 0.01 kcal/mol. The direct AIMD calculations were carried out using our own code. ,, …”

“…The direct AIMD calculations were carried out using our own code. 20,21,23 Direct AIMD calculations of the neutral dimer were carried out under constant vibration temperature conditions (10,77,200, and 300 K) to generate the initial geometries of the structure in the vertical ionized state, [(HCOOH) 2 + ] ver . 24 The Nose−Hoover algorithm was used to maintain a constant temperature in each trajectory.…”

“…In the present study, the direct AIMD method , was applied to model the reaction dynamics of the FA dimer cation following its ionization, in order to elucidate the corresponding reaction mechanism. In particular, we focused on identifying the dominant factor in the branching of the reaction channels.…”

Insight into the CO2 photoreduction mechanism over 9-hydroxyphenal-1-one (HPHN) carbon quantum dots

“…This process requires a considerable transfer of energy and occurs in the electronically excited states. In addition, this process is a redox reaction involving electron transfer during the whole process and especially in the initiation step for CO 2 activation [21][22][23], which is a key challenge and significantly critical for CO 2 reduction. Third, this process is composed of a sequence of steps involving proton transfer, which finally determines the oxidation state of the carbon atom.…”