Sulfur-poisoning on Rh NP but sulfur-promotion on single-Rh1-site for methanol carbonylation

Sulfur poisoning is a severe problem for most noble metal nanoparticle (NP) catalysts, and ppm or ppb levels of sulfur species could result in dramatic activity reduction or even irreversible deactivation. Developing catalysts with high sulfur tolerance is crucial, yet challenging. Here, we reported a clear discovery in methanol carbonylation that sulfur poisoned the Rh NP (Rh/CMK-3) but promoted the single-Rh1-site (Rh1/AC) while the Rh NP (Rh/AC) experienced a process of atomic dispersion. Strong adsorption of sulfur and the formation of the Rh-S passivation layer were supposed to lead to Rh/CMK-3 sulfur poisoning. However, the detrimental H2S transformed into CH3SCH3 and CH3SH on Rh1/AC and then acted as a ligand of Rh atoms, participating in the subsequent reaction, lowering the energy barrier of the rate-determining step, and lastly promoting the reaction. This work provides benefits in solving the sulfur poisoning of metal NP and developing high sulfur tolerant single-metal-site catalysts.