0D/2D MXene Quantum Dot/Ni-MOF Ultrathin Nanosheets for Enhanced N2 Photoreduction

To improve the photocatalytic efficiency of the N2 reduction reaction, MXene quantum dots (Ti3C2-QDs) and two-dimensional (2D) nickel metal–organic framework (Ni-MOF) with different ratios were fabricated by a simple self-assembly strategy to form type II heterojunctions. The resultant composites showed enhanced absorption and excellent interfacial charge-transfer capabilities according to the optical and photoelectron properties. The optimal Ti3C2-QD/Ni-MOF heterostructure exhibited a considerable ammonia yield rate (88.79 μmol gcat–1 h–1). By means of X-ray absorption near-edge fine structure (XANES) technique, it was found that the interaction of Ti3C2-QD and Ni-MOF could accelerate the electron transfer, and Ni site would be the main area to enrich the electron density as well as adsorb and activate N2. Finally, with the aid of density functional theory (DFT) calculations and in situ Fourier transform infrared spectrometry (FTIR), the reaction pathway and intermediate products were studied.