Roles of N-Vacancies over Porous g-C₃N₄ Microtubes during Photocatalytic NO_x Removal

Abstract

The development of catalysts that effectively activate target pollutants and promote their complete conversion is an admirable objective in the environmental photocatalysis field. In this work, graphitic carbon nitride (g-C 3 N 4 ) microtubes with tunable N-vacancy concentrations were controllably fabricated using an in situ soft-chemical method. The morphological evolution of g-C 3 N 4 , from the bulk to the porous tubular architecture, is discussed in detail with the aid of time-resolved hydrothermal experiments. We found that the NO removal ratio and apparent reaction rate constant of the g-C 3 N 4 microtubes were 1.8 and 2.6 times higher than those of pristine g-C 3 N 4 , respectively. By combining detailed experimental characterization and density functional theory calculations, the effects of N-vacancies in the g-C 3 N 4 microtubes on O 2 and NO adsorption activation, electron capture, and electronic structure were systematically investigated. These results demonstrate that surface N-vacancies act as specific sites for the adsorption activation of reactants and photoinduced electron capture, while enhancing the light-absorbing capability of g-C 3 N 4 . Moreover, the porous wall structures of the as-prepared g-C 3 N 4 microtubes facilitate the diffusion of reactants, and their tubular architectures favor the oriented transfer of charge carriers. The intermediates formed during photocatalytic NO removal processes were identified by in situ diffuse reflectance infrared Fourier transform spectroscopy, and different reaction pathways over pristine and N-deficient g-C 3 N 4 are proposed. This study provides a feasible strategy for air pollution control over g-C 3 N 4 by introducing N-vacancy and porous tubular architecture simultaneously. KEYWORDS: N-vacancy, tubular g-C 3 N 4 , porosity, photocatalytic NO x removal

ZIF‐67‐Derived 3D Hollow Mesoporous Crystalline Co3O4 Wrapped by 2D g‐C3N4 Nanosheets for Photocatalytic Removal of Nitric Oxide

“…Among the means of NO degradation, photocatalysis is widely used owing to its low energy consumption and mild operating conditions. Many semiconductor catalysts have been synthesized and studied for NO photooxidation, including TiO 2 , g‐C 3 N 4 , Bi‐based materials, and metal oxides …”

Study on the Macro‐Kinetics of NO Advanced Oxidation Removal by Decomposition of Gas‐Phase H2O2 over γ‐Fe2O3@Fe3O4

“…Although wet flue gas desulfurization and ammonia‐based selective catalytic reduction (NH3‐SCR) processes have been widely used in the coal‐fired power plants for single pollutant removal, which lead to large and complex systems and the high capital and operating costs. In recent years, flue gas purification technologies, including plasma purification technology, adsorption purification technology, photo catalytic oxidation technology and ozone oxidation technology, have shown good development and application prospects. However, most of them are still in the laboratory stage due to technical or economic problems.…”

Intrinsic Defects in Polymeric Carbon Nitride for Photocatalysis Applications

“…Wang et al synthesized Ndeficient PCN porous microtubes through an in situ softchemical method. [38] In situ DRIFTS results revealed that the adsorption sites of NO and O 2 in N-deficient PCN and pristine PCN are N vacancies and terminal NÀ H bonds, respectively. The spatial distribution of nitrogen vacancies not only enhanced the adsorption and activation of NO and O 2 , but also influenced the electron separation behavior.…”

“…[47] Photooxidation and photoreduction via semiconductor photocatalysts are two different methods to remove NO. [38,47] Amongst the above two methods, photooxidation of NO into NO 2 even to NO 3 À was investigated earlier and more likely be accepted by most researchers. For example, Lv and his coworkers explored a sequence of PCN photocatalysts modified with nitrogen or carbon vacancies.…”

“…Wang et al. fabricated porous PCN microtubes with adjustable nitrogen vacancy concentrations [38] . DFT calculations and in situ DRIFTS revealed that nitrogen vacancies contributed to the activation and dissociation of NO and O 2 along with promoting electron separation.…”