Preparation of 0D/2D ZnFe₂O₄/Fe-doped g-C₃N₄ hybrid photocatalysts for visible light N₂ fixation

A photocatalyst which consists of zero-dimension (0D) ZnFe₂O₄ (ZFO) and two-dimension (2D) Fe-doped g-C₃N₄ (Fe-CN) has been prepared successfully through a facile solvothermal method. The Fe doping into g-C₃N₄ lattice has been identified by both the infrared (IR) and X-ray photoelectron spectra (XPS), respectively. Introducing Fe into CN extends the spectral response to 700 nm while ZFO serves as a near infrared (NIR) photosensitizer of the Fe-CN component. The formation of Fe-CN heterostructure not only contributes to visible light absorption but also promotes the separation of photo-generated electron-hole pairs. Furthermore, the density functional theory (DFT) calculation indicated that the N₂ molecules prefer to be adsorbed onto the Fe sites with a reduced potential barrier for N₂ fixation. More importantly, the Fe atoms doped into the CN lattice acted as the reaction sites for accelerating photocatalytic N₂ fixation reaction, which was also demonstrated by DFT. These factors lead to a high photocatalytic NH₄⁺ generation rate of 25.3 mg g⁻¹ h⁻¹ under a full-spectrum irradiation, which is much higher than the value (4.4 mg g⁻¹ h⁻¹) of pure CN catalysts. This research might provide a novel approach for rationally designing full-spectrum-response N₂ fixation photocatalyst.