Performance Exploration of Ni-Doped MoS₂ in CO₂ Hydrogenation to Methanol

The preparation of methanol chemicals through CO₂ and H₂ gas is a positive measure to achieve carbon neutrality. However, developing catalysts with high selectivity remains a challenge due to the irreversible side reaction of reverse water gas shift (RWGS), and the low-temperature characteristics of CO₂ hydrogenation to methanol. In-plane sulfur vacancies of MoS₂ can be the catalytic active sites for CH₃OH formation, but the edge vacancies are more inclined to the occurrence of methane. Therefore, MoS₂ and a series of MoS₂/Ni_x and MoS₂/Co_x catalysts doped with different amounts are prepared by a hydrothermal method. A variety of microscopic characterizations indicate that Ni and Co doping can form NiS₂ and CoS₂, the existence of these substances can prevent CO₂ and H₂ from contacting the edge S vacancies of MoS₂, and the selectivity of the main product is improved. DFT calculation illustrates that the larger range of orbital hybridization between Ni and MoS₂ leads to CO₂ activation and the active hydrogen is more prone to surface migration. Under optimized preparation conditions, MoS₂/Ni_0.2 exhibits relatively good methanol selectivity. Therefore, this strategy of improving methanol selectivity through metal doping has reference significance for the subsequent research and development of such catalysts.