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Carbon-bridged atomically dispersed platinum on MOF-derived ZnO/C for selective photocatalytic oxidation of NO into Nitrates and Nitrites

Lizhen Hu,Jiayou Liu,Xiaoxiang Huang,Qianqian Nie,Penglei Liu,Zhongchao Tan,Hesheng Yu

Using nanoclusters and single atoms with unique activity to replace nanoparticles is a promising strategy to enhance catalyst activity. However, stable loading of nanoclusters and single atoms remain a challenge. This paper reports atomically dispersed Pt bridged with metal-organic framework (MOF)-derived ZnO/C through carbon atoms (Pt–ZnO/C), by impregnation combined with calcination , for photocatalytic oxidation of NO. The MOF-derived ZnO/C has a larger specific surface area than pure ZnO. The presence of C enhances the visible light absorption, promotes the migration of photogenerated carriers , and more importantly facilitates the stabilization of Pt single atoms through Pt–C interactions. The Pt species present in the Pt–ZnO/C catalysts in the form of single atoms and nanoclusters. The Pt–ZnO/C catalysts show high NO conversion rates and selectivity towards NO 3 − /NO 2 − ions formation. Specifically, the NO conversion rate of 81.9% is much higher than those of ZnO/C (31.4%) and Pt nanoparticles loaded ZnO/C (Pt NPs-ZnO/C, 58.6%). In addition, the selectivity of NO 3 − /NO 2 − (i.e., 98.6%) formation over the Pt–ZnO/C catalyst is much higher than that of NO 2 (i.e., 1.4%). Furthermore, the photocatalysis tests and ESR results suggest that the Pt single atoms and nanoclusters can enhance the oxidation of NO by promoting the production of O 2 •- and OH • . The DFT results also reveal that single Pt atoms promote the adsorption of O 2 and H 2 O to form O 2 •- and OH • . More importantly, OH • can promote the selective oxidation of NO to NO 3 − /NO 2 − ions. In addition, the projected density of states of single Pt atoms loaded on the ZnO/C catalysts show that the presence of C atom bridge favors the stability of single Pt atoms because of the interaction between C and Pt atoms. This work provides a new strategy for the design of single-atom-loaded metal oxide catalysts.