Sustainable hydrogen production via CO₂-assisted BH₃ + BH₃ reaction: a computational analysis

The activation and utilization of carbon dioxide (CO₂) for hydrogen production represents a central challenge in the development of sustainable and carbon-neutral energy systems. Borane (BH₃), a potent Lewis acid with high reactivity toward small molecules, has emerged as a promising candidate for CO₂ activation and hydrogen release. However, the mechanistic effects of incorporating multiple CO₂ molecules into BH₃-based systems remain poorly understood. In this study, density functional theory (DFT) calculations were conducted to explore the reaction mechanisms of a dimeric BH₃ system in the presence of zero to three CO₂ molecules. Potential energy surfaces were constructed at the M06-2X/6-311++G(3df,2p) level to identify key intermediates, transition states, reaction energies, and activation barriers. The computational results reveal a stepwise mechanism involving BH₃-CO₂ adduct formation and distinct transition states, with CO₂ playing a significant role in modulating both thermodynamic stability and kinetic accessibility. Notably, the inclusion of CO₂ stabilizes multi-component complexes and lowers activation barriers, thereby facilitating hydrogen release. These findings underscore the dual function of CO₂ as both a structural stabilizer and an energetic facilitator, offering valuable insights into CO₂ valorization and hydrogen generation in the context of sustainable energy applications.