Entropy production and chemical reactions in nonequilibrium plasma

In this work, methods based upon nonequilibrium thermodynamics are elucidated to predict stationary states of chemical reactions in nonequilibrium plasma, and limits for energy conversion efficiency. CO₂ splitting is used as an example reaction. Expectations from the theoretical framework are compared to experimental results, and reasonable agreement is obtained. The key conclusion is that the probability of observing either reactants or products increases with the amount of energy dissipated by that side of the reaction as heat through collisions with hot electrons. The side of the reaction that dissipates more energy as heat has a higher probability of occurrence. Furthermore, endergonic chemical reactions in nonequilibrium plasma, such as CO₂ splitting at low temperature, require an intrinsic energy dissipation to satisfy the second law of thermodynamics—a sufficient and necessary waste. This intrinsic dissipation limits the maximum theoretical energy conversion efficiency.