NO disproportionation over defective 1T'-MoS2 monolayers
MoS2 monolayers are usually born with vacancies (most likely missing S atoms). Here, by using the first-principles calculations, we prove that 1T'-MoS2 monolayers are an efficient catalyst for NO disproportionation. The reaction starts with NO adsorptions at the S vacancies. Later coming NO molecules react with the already adsorbed ones to afford NO2 molecules, which readily desorb. The remaining N-doped MoS2 sheets can then easily react with NO molecules to produce N2O, which can be heated to desorb. Thus, the S vacancies are recovered and the catalytic cycle is completed. The NO2 formation step has a relatively high barrier of 1.58 eV, but it can be lowered to 0.19 and 0.56 eV by applying biaxial -3% and 3% strain, respectively. The reaction mechanism is totally different from those catalyzed by metal-centered catalysts (complexes, clusters, or metal-organic frameworks), which feature the N2O formation as the rate-limiting step and NO2 in the metal-nitrite complexes cannot be released. Our work paves the way of strain engineering two-dimensional (2D) materials into efficient NO disproportionation catalysts.