The transformation of CO₂, a significant greenhouse gas, into valuable products has become a central focus in our pursuit of a decarbonized energy future. However, the strong C=O bonds in CO₂ present both kinetic and thermodynamic challenges. To overcome these obstacles, traditional high-temperature processes like CO₂ hydrogenation are employed. However, maintaining high temperatures is challenging and not energy-efficient. An alternative approach is plasma catalysis, where catalytic surface activation is combined with plasma activation in the gas phase. Within a plasma environment, excited electrons collide with gas molecules, leading to the formation of radicals, ions, or causing molecular dissociations. In this study, we developed an eReaxFF force field for simulating CO₂ reduction under plasma conditions in the gas phase. The eReaxFF is an explicit electron force field that has been trained against quantum mechanical (QM) data, ensuring that it accurately captures the underlying electronic interactions during chemical reactions. This method allows us to model phenomena that are critical for understanding reaction mechanisms, such as charge transfer and bond dissociations. Using this eReaxFF description, we predicted an energy barrier of 195 and 180 kcal/mol for CO₂ neutral and CO₂ cation dissociation respectively. We additionally evaluated the energy barriers for CO₂ cationization by radicals—such as the Ar radical cation—in a plasma gas-phase environment. We then ran Molecular Dynamics (MD) simulations to demonstrate our eReaxFF force field capability in timescales beyond the reach of quantum mechanical methods. Particularly, we simulated electron bombardments on neutral CO₂ and identified the dissociation pathways resulting from ion and radical collisions with CO₂. By explicitly modeling electron behavior, this force field helps clarify the mechanisms of charge transfer, bond activation, and subsequent reactions, therefore providing valuable insights into the complex chemistry involved in plasma-assisted CO₂ conversion. In future work, we aim to incorporate catalyst descriptions to analyze both catalytic interfaces and plasma effects in CO₂ reduction.
