Uranium-Doped Induced 5f-π Orbital Hybridization Promotes CO<sub>2</sub> Reduction to C<sub>2+</sub> Products on MXenes (M = Ti, Zr, Hf) Monolayers
Jin-Hao Xu, Zhimin Dong, Zhibin Zhang, Yunhai Liu, Shu‐Xian Hu
Abstract
Photocatalytic CO 2 reduction into high-value C 2+ products is quite exciting but challenging since the transition paths of photogenerated electron and excited-state active sites during photocatalysis are still. Herein, we investigated the process of reducing CO 2 in uranium-doped M 3 C 2 O 2 0 materials (M = Ti, Zr, and Hf) from the perspectives of detailed interfacial structure evolution and reaction mechanism. Among the three materials and four models, UHf 3 C 2 O 2 x –1 exhibits the best CO 2 photoreduction performance with a CO yield of 273.44 μmol·g –1, 2.4 times higher than that of Hf 3 C 2 O 2 x –1 (113.67 μmol·g –1 ). In-depth experimental and theoretical studies reveal that the doping of tetravalent uranium plays a crucial role in the activation of CO 2 . The effective orbital hybridization between the U f z 3 orbital and the CO 2 Π* molecular orbital induces electron spin polarization, which significantly reduces the activation energy. The mechanism of *CHO coupling occurs in the process of UHf 3 C 2 O 2 x –1 catalyzing the formation of C 2+ products, which has a significantly lower energy barrier than that of the traditional *CO coupling process. This interpretation indicates that adjusting the oxidation state of uranium can tune the electronic structure and catalytic performance of the UM 3 C 2 O 2 x –1 . This work provides novel insights into the behavior of f-electrons in the reaction mechanism and predicts catalysts containing uranium.