Journal of Thermodynamics & Catalysis
Open Access

Thermodynamic Insights into the Engineering of Nano-Catalysts for CO2 Reduction Reactions

Kazunari Domen^{* *}Correspondence: Kazunari Domen, Department of Chemical System Engineering, University of Tokyo, Bunkyo, Japan, Email:

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As the global demand for sustainable energy sources increases, carbon dioxide Reduction Reactions (CO₂RR) have emerged as a promising strategy to mitigate climate change while simultaneously producing valuable chemicals. The electrochemical conversion of CO₂ into useful products such as hydrocarbons, alcohols, and acids is of great interest in the context of renewable energy storage and carbon capture technologies. One of the main challenges of CO₂RR is the identification and optimization of suitable catalyst materials that can effectively lower the activation energy of CO₂ conversion reactions. CO₂ reduction is a complex multi-electron process that involves the transformation of CO₂, a stable molecule, into more reactive compounds. The electrochemical pathway can produce a variety of products depending on the reaction conditions, the catalyst, and the applied potential. However, this reaction can proceed through various intermediates, leading to the formation of different products such as CO, methane (CH₄), ethylene (C₂H₄), and even liquid fuels. The challenge lies in guiding the reaction towards the desired products with high efficiency and selectivity. Nano-catalysts, with their high surface area, tunable electronic properties, and the ability to expose active sites in novel ways, offer significant advantages over bulk materials in CO₂RR.

The feasibility of CO₂ reduction can be analyzed by the change in the Gibbs free energy of the reaction. A reaction is thermodynamically favoured when the Gibbs free energy is negative. In the case of CO₂ reduction, understanding the ΔG for various reaction intermediates is essential to identify catalyst materials that lower the activation energy and drive the reaction in the desired direction. For example, nano-catalysts with lower ΔG values for specific intermediates, such as CO or formate (HCOO⁻), can improve reaction efficiency. The volcano diagram is a useful concept in catalysis, particularly for understanding the relationship between catalyst performance and the binding energy of the intermediates. In CO₂RR, the main intermediate is usually CO, which is formed during the reduction of CO₂. Nano-catalysts must have an optimal binding energy for CO, which is too low and the intermediate will desorb too quickly, while too strong an interaction can lead to catalyst poisoning. Thermodynamic models, such as the volcano diagram, help predict the optimal binding energy for different catalysts and guide the design of nano-materials with the appropriate electronic structure for optimal performance.

The size, shape, and morphology of nano-catalysts have a profound influence on their catalytic properties. At the nanoscale, the increase in surface area and the distribution of active sites play an important role in improving the efficiency of CO₂ reduction. Thermodynamic simulations allow researchers to model the effect of nanostructure on reaction pathways and intermediate stability, guiding the design of nano-catalysts that expose more active sites while maintaining favourable thermodynamic conditions for CO₂RR. One of the main challenges of CO₂ reduction is overcoming the high growth rates required to drive the reaction. Overvoltage is the additional voltage required beyond the thermodynamic requirement to overcome the activation energy barrier. For example, incorporating specific ligands or tuning the electronic properties of the catalyst by alloying or doping can help reduce overvoltage, thereby improving the overall efficiency of the CO₂RR process.