Dual-Shelled CeO₂ Hollow Spheres Decorated with MXene Quantum Dots for Efficient Electrocatalytic Nitrogen Oxidation

Electrocatalytic nitrogen oxidation (NOR) provides a promising alternative strategy for synthesizing nitric acid from widespread N₂, which overcomes the disadvantages of Haber-Bosch-Ostwald process. However, the NOR process suffers from the limitation of high N≡N bonding energy, sluggish kinetics, and low efficiency. It is prerequisite to develop more efficient NOR electrocatalysts. Herein, dual-shelled CeO₂ hollow spheres (D-CeO₂) are synthesized and modified with Ti₃C₂ MXene quantum dots (MQDs) for NOR, which exhibited a NO₃ ^- yield rate of 71.25 µg h^-1 mg_cat ^-1 and Faradic Efficiency (FE) of 31.80% at 1.7 V versus RHE. The unique quantum size effect and abundant edge active sites lead to more effective capture of nitrogen. Moreover, the dual-shelled hollow structure will gather intermediate products in the interlayer of the core-shell to facilitate N₂ fixation. The in situ Fourier transform infrared (FTIR) spectroscopy confirmed the formation of *NO and NO₃ ^- species during the NOR, and the kinetics and possible pathways of NOR are calculated by density functional theory (DFT). In addition, a Zn-N₂ reaction device is assembled with D-CeO₂/MQDs as anode and Zn plate as cathode, obtaining an extremely high NO₃ ^- yield rate of 104.57 µg h^-1 mg_cat ^-1 at 1 mA cm^-2.