Although substantial advances have been made in a few reactions of industrial significance over single-atom catalysts (SACs), the origin of the superior catalytic performance, the nature of the active sites, and the reaction pathways are still the subject of debate. Even for CO oxidation over SACs on nonreducible substrates, the understanding is limited. We investigated the performance of Pd atoms monodispersed on graphene (PdGr) in CO oxidation. Combining firstprinciples-based thermodynamics calculations and microkinetics modeling, we showed that the positively charged PdGr can exhibit a rather high low-temperature activity in CO oxidation. Under reaction conditions, the Pd atom binds strongly with O 2 , acting as the reactive species to convert CO. A comparison of the conversion rates of steps along different potential reaction pathways provides direct evidence that CO oxidation mainly proceeds through revised Langmuir−Hinshelwood pathways, and the dissociation of the peroxide intermediate (O−O−CO) is the ratelimiting step. The predicted catalytic performance was attributed to the specific electronic structure of PdGr with the positively charged Pd on graphene monovacancy exposing sp-type frontier states. We expect these findings to help in understanding the performance of SACs and to guide the design and fabrication of SACs with superior catalytic performance.

Catalytic semireduction of internal alkynes to alkenes is very important for organic synthesis. Although great success has been achieved in this area, switchable Z/E stereoselectivity based on a single catalyst for the semireduction of internal alkynes is a longstanding challenge due to the multi-chemo- and stereoselectivity, especially based on less-expensive earth-abundant metals. Herein, we describe a switchable semireduction of alkynes to (Z)- or (E)-alkenes catalyzed by a dinuclear cobalt complex supported by a macrocyclic bis pyridyl diimine (PDI) ligand. It was found that cis-reduction of the alkyne occurs first and the Z–E alkene stereoisomerization process is formally controlled by the amount of H2O, since the concentration of H2O may influence the catalytic activity of the catalyst for isomerization. Therefore, this protocol provides a facile way to switch to either the (Z)- or (E)-olefin isomer in a single transformation by adjusting the amount of water.

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The lack of efficient catalysts with a wide working temperature window and vital O2 and SO2 resistance for selective catalytic reduction of NO by CO (CO‐SCR) largely hinders its implementation. Here, a novel Ir‐based catalyst with only 1 wt% Ir loading is reported for efficient CO‐SCR. In this catalyst, contiguous Ir atoms are isolated into single atoms, and Ir–W intermetallic nanoparticles are formed, which are supported on ordered mesoporous SiO2 (KIT‐6). Notably, this catalyst enables complete NO conversion to N2 at 250 °C in the presence of 1% O2 and has a wide temperature window (250–400 °C), outperforming the comparison samples with Ir isolated‐single‐atomic‐sites and Ir nanoparticles, respectively. Also, it possesses a high SO2 tolerance. Both experimental results and theoretical calculations reveal that single Ir atoms are negatively charged, dramatically enhancing the NO dissociation, while the Ir–W intermetallic nanoparticles accelerate the reduction of the N2O and NO2 intermediates by CO.