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Author: search.filters.author.Bureekaew, SareeyaSubject: search.filters.subject.DFT calculations

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    Hydrogenation of CO2 to formic acid catalyzed by Co and Cu Single-atom catalysts supported on MOF-808: A DFT investigation
    (2024-12-01)
    Kusonjariyakun, Nawarat
    ;
    Santatiwongchai, Jirapat
    ;
    Meeprasert, Jittima
    ;
    Chotpatiwetchkul, Warot
    ;
    Maihom, Thana
    In this work, DFT-based calculations and microkinetic modeling were employed to investigate CO<inf>2</inf> hydrogenation to formic acid using H<inf>2</inf> over Co and Cu single-atom catalysts supported on MOF-808. We investigated two pathways: one without the introduction of a second H<inf>2</inf> molecule (pathway A) and another one with it (pathway B). Pathway B, which involves introducing the second H<inf>2</inf> molecule alongside the formate intermediate from the first step, exhibits significantly lower energy barriers (three times lower) for the transformation into formic acid in the second step of CO<inf>2</inf> hydrogenation. Moreover, pathway B shifts the reaction thermodynamics from endergonic to exergonic, highlighting its kinetic and thermodynamic advantages. Notably, we observed formate intermediates with quasi-bidentate geometry alongside the prevalent bidentate chelating geometry. Cu<sup>2+</sup>-MOF-808 exhibits superior catalytic activity compared to Co<sup>2+</sup>-MOF-808, attributed to Cu's stronger preference for stabilizing the transition state in its square planar geometry through the Jahn-Teller effect, which is less effective in Co. Furthermore, our microkinetic modeling consistently confirms that Cu<sup>2+</sup>-MOF-808 outperforms Co<sup>2+</sup>-MOF-808 at lower temperatures, with the rate of formic acid production depending on the concentration of H<inf>2</inf>. The desorption of formic acid is identified as the rate-determining step of the reaction, significantly impacting overall efficiency.