Theoretical Insight Into The Conversion Of Greenhouse Gases To Methanol On Single-atom Catalysts

Utilizing carbon dioxide（CO₂）and methane（CH₄）as carbon sources for methanol（CH₃OH）production is a promising solution to the dual crisis of global energy shortages and climate change.Due to the high symmetry and stability of CO₂ and CH₄ molecules,the development of highly efficient catalysts is essential for realizing this process.Recently,single-atom catalysts exhibit tremendous potential in the conversion of CO₂ and CH₄ to CH₃OH owing to their unique electronic and geometric structures.The challenge currently faced is to rationally design efficient single-atom catalysts,and a deep understanding of their catalytic mechanisms is key to driving this process.Herein,we employed density functional theory（DFT）calculations to investigate the micro-mechanism of SACs in the conversion of CO₂ and CH₄ to CH₃OH,and simultaneously predicted various high-performance SACs,aiming to provide important guidance for the rational design of efficient catalysts.Related research works are summerized as follows:（1）The catalytic performance of single metal atoms supported on graphene for the direct oxidation of CH₄ to CH₃OH（DMTM）were studied.The results revealed that Co₁/G exhibited significantly improved catalytic activity compared to other metals.The rate-determining step of Co₁/G was the dissociation of the C-H bond in CH₄,and its energy barrier can be lowered to 0.80 e V,which was expected to exhibit DMTM catalytic activity at room temperature.Moreover,Co₁/G exhibited high selectivity for CH₃OH by suppressing the production of by-products through increasing the dissociation energy barrier of*CH₃ intermediate.The strong interaction between Co atoms and graphene resulted in high thermodynamic stability of Co₁/G.（2）The catalytic performance of single metal atoms supported on graphene-like hexagonal boron nitride（h-BN）with varying coordination environments for DMTM was further investigated.The results revealed that Cu supported on oxygen-doped h-BN featuring one O atom and two N atoms coordination exhibited higher catalytic activity,selectivity,and stability compared to other single metal atoms.The key factors contributing to the enhancement of catalytic performance were the moderate adsorption energy of the*O,high stability of*CH₃,and low desorption energy of*CH₃OH.Moreover,we proposed the adsorption energy of the*O as an effective descriptor for designing and screening high-activity catalysts,providing new opportunities for identifying efficient catalysts in a rapid and cost-effective manner.（3）A novel highly selective Cu single-atom catalyst for CO₂hydrogenation to CH₃OH was designed using a surface group modification strategy.To investigate the influence of Cu single atoms and surface groups on catalytic performance,three types of imine groups were constructed on Pd（111）surface doped with Cu single atoms through an aldehyde-amine condensation reaction.The results indicated that the synergistic catalytic effect of the imine groups and Cu single atoms reduced the energy barrier of the rate-determining step from 1.00 e V to 0.72 e V,thereby considerably enhancing the catalyst’s activity.The imine groups modulated the electronic structure of the active sites,promoting greater electrons flow into the anti-bonding orbitals of CO₂,while the Cu atoms enhanced CO₂adsorption and improved the stability of the imine groups.Moreover,the difference in the number of electrons obtained by the groups before and after CO₂ adsorption could be utilized to predict the catalytic activity of the group-modified single-atom alloy catalysts,thereby accelerating the screening of highly efficient catalysts.（4）The catalytic performance of Pt₁ single-atom（Pt₁@graphene）and Pt₂ dimers（Pt₂@graphene）supported on graphene for CO₂hydrogenation were explored.The results indicated that Pt₁@graphene and Pt₂@graphene exhibited significant differences in catalytic properites,especially in catalytic selectivity.Pt₁@graphene tended to produce formic acid,while Pt₂@graphene preferred CH₃OH production.The difference in product selectivity was attributed to the synergistic effect of adjacent Pt atoms in Pt₂@graphene,which facilitated*COOH hydrogenation to*C（OH）₂ intermediate and ultimately altered the CO₂ hydrogenation pathway.95 Figures,12 Tables and 204 References...