Carbon dioxide (CO₂) reduction to value-added fuels and chemicals, utilizing electricity generated from clean energy sources, holds great promise for addressing environmental pollution and the energy crisis. However, the widespread utilization of catalysts is hindered by the challenge of poor product selectivity at low overpotentials. To overcome this obstacle, significant efforts are being made to enhance catalyst activity and product selectivity. Two-dimensional (2D) materials exhibit extraordinary properties such as large surface area, high electrical conductivity, abundant active sites, and quantum effects, which make them highly promising as electrocatalysts. In the field of chemistry, traditional approaches often involve a trial-and-error process, which can be time-consuming and resource-intensive. However, there is good news as theoretical calculations have emerged as a powerful tool for the efficient and cost-effective prediction of catalyst performance. In this thesis, we conducted a comprehensive investigation into the CO₂ reduction performance of several representative 2D materials using density functional theory (DFT) as the theoretical framework. By leveraging theoretical calculations, we have successfully screened and identified some exceptional catalysts for CO₂ reduction, which will effectively guide experimental researchers in designing advanced catalysts.

Firstly, we investigated the effect of environmentally friendly Ti, Fe, Ni, Cu, Zn, In, and Sn metals anchored on 2H phase WTe₂ materials (M@WTe₂) on CO₂ reduction. The binding energy excludes In and Sn metals with weak binding, and the free energy diagram screens out Ni as a promising catalyst for HCOOH production with the lowest limiting potential. Moreover, Ni@WTe₂ demonstrates excellent selectivity, effectively suppressing the formation of multi-carbon products and hydrogen evolution reaction (HER). Single atom Ni also has good stability and can be stably anchored on the WTe₂ surface without forming clusters due to the high diffusion energy barrier. All the above confirm that Ni@WTe₂ is an ideal catalyst.

Secondly, we conducted a comprehensive examination of ten single-atom 3d transition metals (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) anchored on a planar B5N3 monolayer and screening favorable CO2 electrocatalytic reduction pathways employing spin-polarized DFT calculations with van der Waals corrections. We performed ab initio molecular dynamics (AIMD) simulations of B₅N₃ as well as 3d transition metal anchored B₅N₃ structures and found that they are all thermodynamically stable. Then, we analyzed CO₂ adsorption, which is the initial and critical step for the subsequent hydrogeneration. The results demonstrate that most of the transition metals, ranging from Sc to Cu, enhance the adsorption of CO₂ compared to B₅N₃, except for Zn. Additionally, these anchored metals also enhance the inherently low CO₂ reduction activity of B₅N₃, particularly Ni, exhibiting a high selectivity towards CH₄ with a relatively low limiting potential (-0.21 V vs. reversible hydrogen electrode), where the conversion of CH₃ to CH₄ is the potential-determining step.

Thirdly, seven stable molecular dual-atom M-N-C (M = Fe, Co, and Ni) catalysts with a unique 5 N-coordination were investigated for nitrogen reduction reaction (NRR). By analyzing the surface Pourbaix diagrams, we identified three catalysts, namely N₃-Ni-Ni-N₂, N₃-Co-Ni-N₂, and N₃-Ni-Co-N₂, for further investigation of their activity in NRR. The results indicate that N₃-Co-Ni-N₂ exhibits great promise as an NRR catalyst with a relatively low ΔG of 0.49 eV. This study emphasizes the significance of analyzing surface states under electrochemical conditions prior to conducting activity analysis in catalyst design.

Finally, the surface Pourbaix diagram, as a function of potential and pH, is further used to analyze the surface states of 2D AlN, GaN, InN, SiC, GeC, and SnC materials, identifying five materials with available sites under operating conditions. AlN and SiC emerge as promising catalysts for HCOOH production, exhibiting low reaction free energies of 0.48 and 0.47 eV for the rate-determining step, respectively. In addition, the results showed that the first protonation is to form OCHO*, whose two atoms bonded to the substrate, and two bonds have similar negative ICOHP values and work synergistically to make OCHO* bind strongly to the substrate. This further explains the tendency for the product to favor HCOOH over CO.

In summary, we explore the modulation of catalytic performance in 2D materials using various methods or perspectives, with the expectation of providing new insights and theoretical foundations for the effective design and screening of highly active and selective 2D catalysts.