Nitrogen-defective g-C3N4 with enhanced photocatalytic performance fabrication by destructing C N C bond via H2O2

Electrostatic self-assembled layered polymers form supramolecular heterojunction catalyst for photocatalytic reduction of high-stability nitrate in water

In this work, two polymers are connected by electrostatic self-assembly method to form a supramolecular heterojunction to remove pollutants. g-C₃N₄-Cl/PANI catalyst can be used for photocatalytic reduction of nitrate in water, and the nitrogen selectivity reaches 98.2%. Specially, charge density analysis and comparative experiments showed that the introduction of covalent chlorine increased in electron transfer conduction between layers. In addition, differential charge density and solid EPR tests reveal high electron density and electron transfer pathways for supramolecular heterostructures. The results of the work function give direct evidence for the high catalytic performance of the supramolecular heterojunction. The reasons and active species of photocatalytic reduction of nitrate by g-C₃N₄-Cl and g-C₃N₄-Cl/PANI are compared. The catalyst exhibits the performance of highly reducing nitrate to harmless nitrogen with the contribution of supramolecular heterojunction and covalent chlorine. In short, a new idea of constructing a supramolecular photocatalyst is proposed, which can be applied to efficiency reduce nitrate in water.

N-doping TiO2 hollow microspheres with abundant oxygen vacancies for highly photocatalytic nitrogen fixation

Photocatalytic fixation of nitrogen to ammonia (NH₃) is a green but low-efficiency technology due to the high recombination of photo-generated carriers and poor light absorption of photocatalysts. Generally, the adsorption capacity for N₂ and the band position of TiO₂ are responsible for bandgap, light-adsorption, and the separation of photocarriers. Therefore, they play crucial roles to improve catalytic activity. Herein, N-doping TiO₂ hollow microspheres (NTO-0.5) with oxygen vacancies were synthesized via a hydrothermal method using phenolic resin microsphere as a template. The obtained NTO-0.5 achieves an impressive ammonia yield of 80.09 μmol g_cat^-1h^-1. Oxygen vacancies of NTO-0.5 were confirmed by ESR, Raman, XPS, Zeta potential, and H₂O₂ treatment for reducing oxygen vacancies. The ammonia yield of NTO-0.5 decreases to 34.78 μmol g_cat^-1h^-1 after reducing oxygen vacancies by H₂O₂ treatment, which demonstrates the importance of oxygen vacancies. The oxygen vacancies narrow the bandgap from 3.18 eV to 2.83 eV and impede the recombination of photo-generated carriers. The hollow microspheres structure is conducive to light absorption and utilization. Therefore, the synergistic effect between the oxygen vacancies and the hollow microspheres structure boosts the efficiency of photocatalytic nitrogen fixation. After four cycles, the ammonia production yield still maintains at 76.52 μmol g_cat^-1h^-1, meaning high stability. This work provides a new insight into the construction of catalysts with oxygen vacancies to enhance photocatalytic nitrogen fixation performance.

Plasma-Tuned nitrogen vacancy graphitic carbon nitride sphere for efficient photocatalytic H2O2 production

Graphitic carbon nitride (CN) is a promising photocatalyst for sustainable energy conversion. Meanwhile, N vacancies are useful for H₂O₂ generation; however, they are hard to control. In this study, the N vacancy CN sphere (NVCNS) is synthesized by H₂ plasma treatment to tune the NV. The as-synthesized NVCNS exhibits an efficient and stable photocatalytic H₂O₂ yield of 4413.1 μmol g_cat^-1h^-1, which is 2.5 and 4.6 times higher than that of CNS (1766.4 μmol g_cat^-1h^-1) and bulk CN (956.6 μmol g_cat^-1h^-1), respectively, using a Xe lamp with an intensity of 100 mWcm^-2. In particular, the charges recombination rate is remarkably reduced by introducing N defect state, promoting electron accumulation and O₂ adsorption, through theoretical calculation and experiments. Furthermore, the NV creates abundant unsaturated sites and induces strong interlayer interactions, leading to effective electronic excitation and the promotion of charge transport.