Uranium-Doped Induced 5f‑π Orbital Hybridization Promotes CO2 Reduction to C2+ Products on MXenes (M = Ti, Zr, Hf) Monolayers

• Published in: Journal of physical chemistry. C 2024-01, Vol.128 (2), p.732-742
• Main Authors: Xu, Jin-Hao, Dong, Zhi-Min, Zhang, Zhi-Bin, Liu, Yun-Hai, Hu, Shu-Xian
• Format: Article
• Language: English
• Subjects: C: Energy Conversion and Storage
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.3c06353

Photocatalytic CO2 reduction into high-value C2+ 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 CO2 in uranium-doped M3C2O2 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, UHf3C2O2x–1 exhibits the best CO2 photoreduction performance with a CO yield of 273.44 μmol·g–1, 2.4 times higher than that of Hf3C2O2x–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 CO2. The effective orbital hybridization between the U f z 3 orbital and the CO2 Π* molecular orbital induces electron spin polarization, which significantly reduces the activation energy. The mechanism of *CHO coupling occurs in the process of UHf3C2O2x–1 catalyzing the formation of C2+ 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 UM3C2O2x–1. This work provides novel insights into the behavior of f-electrons in the reaction mechanism and predicts catalysts containing uranium.