Breaking the Trade-Off between CO Tolerance and Intrinsic Activity in Hydrogenation on Metal Oxide-Supported Noble Metal Single Atoms through Coordination Environment Engineering
Xiaojun Zhao, Liqiang Wang, Guangji Zhang, Ping An, Min Yu, Lizhen Lian, Chengcheng Zhang, Dachen Ouyang, Yuchen Yan, Limiao Chen, Tiechui Yuan, You‐Nian Liu
Abstract
Downsizing the metal center to a single atom could enhance the CO tolerance of metal oxide-supported noble metals in catalytic hydrogenation. However, the dissociation of H 2 on such single-atom catalysts is weakened; meanwhile, it tends to produce heterolytic active H species, i.e., M–H δ+ and O–H δ−, and breaking O–H δ−, a key or even rate-determining step, requires a high energy barrier. The situation mentioned above can inevitably compromise the intrinsic activity. Herein, coordination environment engineering is proven to be able to break such a “seesaw effect” between CO tolerance and intrinsic activity in catalytic hydrogenation. Specifically, we construct N-doped metal oxide-supported noble metal single atoms (e.g., Pt 1 /N-MoO 2 ), which exhibit high CO tolerance compared to Pt nanoparticles supported on MoO 2 (Pt NPs/MoO 2 ) and commercial Pt/C. More importantly, the turnover frequency (TOF) of Pt 1 /N-MoO 2 for nitrobenzene hydrogenation is 2.8 times that of Pt 1 /MoO 2, despite both possessing high CO tolerance. Experimental and theoretical studies show that N-doped MoO 2 support tune the electron-deficiency feature of Pt single atoms, leading to weaker CO adsorption than nanoparticles. Meanwhile, the dissociation of H 2 and breaking of O–H δ− occur more readily on Pt 1 /N-MoO 2 than Pt 1 /MoO 2, affording Pt 1 /N-MoO 2 better intrinsic activity. Lastly, this coordination environment engineering can be extended to other metal oxide-supported noble metals, affording high CO tolerance and improved intrinsic activity.