Engineering the electronic structure towards enhanced performances of CO2 adsorption and conversion of a Ti-doped MoS2 monolayer: a DFT study

Abstract

The active site of MoS₂, predominantly located at the crystalline edge, limits selectivity for the CO₂ reduction reaction (CO₂RR). Single-Atom Catalysts (SACs), have emerged as a promising avenue to enhance the catalytic performance of MoS₂, owing to their high catalytic selectivity on the basal plane and tunable activity in various chemical reactions. In this regard, transition metals from the 8B and 1B groups (Cr, Cu, Sc, Ti, V, and Ni) were investigated as dopants on the basal plane for the first time, employing first-principles calculations based on a 4 × 4 × 1 supercell of the MoS₂ monolayer. The Ti/MoS₂ catalyst was identified as the most stable among the SACs, attributed to its optimal formation energy. Various Ti-doped models were analyzed, encompassing energy band structure, density of states, charge differential density, Bader charge, and Gibbs free energy. Our findings indicate that Ti induces diminished electron binding, thereby weakening CO with lower energy, consequently enhancing the availability of surface sites and facilitating catalytic reactions. In our investigation of possible reaction pathways, the preferred CO₂RR pathway was identified as the reverse water gas conversion (RWGS), with the rate-limiting step being CO₂ hydrogenation into carboxyl (*COOH). The Ti modification model on the MoS₂ basal surface demonstrated exceptional catalytic performance, reducing the rate-limiting step to 0.177 eV, which is 17 times lower than that of pure MoS₂. These calculational results provide valuable theoretical insights for designing highly efficient SACs on MoS₂-based functional materials.