Breaking the Trade-Off\nbetween CO Tolerance and Intrinsic\nActivity in Hydrogenation on Metal Oxide-Supported Noble Metal Single\nAtoms through Coordination Environment Engineering

Downsizing the metal center to a single atom could enhance\nthe\nCO tolerance of metal oxide-supported noble metals in catalytic hydrogenation.\nHowever, the dissociation of H<sub>2</sub> on such single-atom catalysts\nis weakened; meanwhile, it tends to produce heterolytic active H species,\ni.e., M–H<sup>δ+</sup> and O–H<sup>δ−</sup>, and breaking O–H<sup>δ−</sup>, a key or even\nrate-determining step, requires a high energy barrier. The situation\nmentioned above can inevitably compromise the intrinsic activity.\nHerein, coordination environment engineering is proven to be able\nto break such a “seesaw effect” between CO tolerance\nand intrinsic activity in catalytic hydrogenation. Specifically, we\nconstruct N-doped metal oxide-supported noble metal single atoms (e.g.,\nPt<sub>1</sub>/N-MoO<sub>2</sub>), which exhibit high CO tolerance\ncompared to Pt nanoparticles supported on MoO<sub>2</sub> (Pt NPs/MoO<sub>2</sub>) and commercial Pt/C. More importantly, the turnover frequency\n(TOF) of Pt<sub>1</sub>/N-MoO<sub>2</sub> for nitrobenzene hydrogenation\nis 2.8 times that of Pt<sub>1</sub>/MoO<sub>2</sub>, despite both\npossessing high CO tolerance. Experimental and theoretical studies\nshow that N-doped MoO<sub>2</sub> support tune the electron-deficiency\nfeature of Pt single atoms, leading to weaker CO adsorption than nanoparticles.\nMeanwhile, the dissociation of H<sub>2</sub> and breaking of O–H<sup>δ−</sup> occur more readily on Pt<sub>1</sub>/N-MoO<sub>2</sub> than Pt<sub>1</sub>/MoO<sub>2</sub>, affording Pt<sub>1</sub>/N-MoO<sub>2</sub> better intrinsic activity. Lastly, this coordination\nenvironment engineering can be extended to other metal oxide-supported\nnoble metals, affording high CO tolerance and improved intrinsic activity.