Efficient photocatalytic NO removal with inhibited NO2 formation and catalyst loss over sponge-supported and functionalized g-C3N4

In-situ generated metallic Bi accelerating Z-scheme charge transfer in Bi2O3/Bi/PCN heterojunction for highly efficient photocatalytic NO oxidation

Artificial Z-scheme photocatalytic systems, inspired by natural photosynthesis, have been widely employed for pollutant removal. In this study, we fabricated a ternary Z-scheme Bi2O3/Bi/porous carbon nitride (PCN) heterojunction with an intimately coupled interface through a simple EG-assisted solvothermal approach to improving photocatalytic performance of NO oxidation. The in-situ generated metallic Bi acts as an electron mediator, effectively accelerating the separation and transfer of photoexcited carriers. The unique Z-scheme charge transfer mechanism provides the strong redox abilities and isolates the active sites for specific reactions, thus promoting photocatalytic NO oxidation activity. As a result, the optimized Bi2O3/Bi/PCN sample achieved a NO removal efficiency of 94.6%, outperforming single-component catalysts and most previously reported heterojunction-based photocatalysts. Additionally, in-situ Fourier transform infrared spectroscopy was employed to propose the NO removal mechanism, offering valuable insight into the conversion pathway. Such a heterogeneous Z-scheme photocatalytic system with a strong redox ability, high charge-separation efficiency, and long-term stability, demonstrates significantly enhanced photoactivity for pollutant removal and is expected to attract increasing interest for other photocatalytic applications.

Nickel atoms of nickel foam simultaneously mediated charge redistribution and firm immobilization of zinc oxide for safe and efficient photocatalytic nitrogen oxide removal

Photocatalytic technology has emerged as a promising solution for air purification of ppb-level nitrogen oxides (NOx), but potential risk of secondary pollution should not be overlooked, which could be triggered by the production of toxic intermediate and the potential release of airborne catalyst particles during reaction processes. Herein, nickel foam (NF) has been introduced as not only carrier material but also performance promoter for zinc oxide (ZnO). The NF supported ZnO sample (Ni-ZnO/NF) demonstrates multifunctional superiority: 66.4 % nitric oxide (NO) removal efficiency, <1.7 % nitrogen dioxide (NO2) byproduct generation, and ultralow photocatalyst loss (<1.2 % mass). Mechanistic investigations combining experimental characterization and theoretical simulations reveal atomic substitution processes where NF-derived Ni atoms replace Zn sites in the ZnO lattice, forming stable Ni-O interfacial bonds, which contributes to enhance interaction between ZnO and NF for firm immobilization and form electron localization zones around Ni-O bond for reactants activation and reactive oxygen species formation. The optimized reaction pathway (NO + e- → NO-, NO- + 1O2 → NO3-) ensures complete oxidation while suppressing hazardous intermediates. This work blueprints next-generation supported photocatalysts through atomic-level interface engineering, advancing practical application of photocatalytic technology for sustainable air purification.

Highly efficient photocatalytic removal of NO and synchronous inhibition of NO2via heterojunction formed by ZnAl-LDH and MXene-Ti3C2-derived TiO2@C

The key challenge in oxidizing NO using photocatalysis is controlling the selectivity of products to avoid the generation of toxic byproducts like NO2. Here, we propose regulating the generation of reactive oxygen species by constructing Type-II heterojunctions to facilitate the deep oxidation of NO to nitrates. Experimental characterization and Density functional theory (DFT) simulations demonstrate that the outstanding photocatalytic activity of heterojunction materials stems from their superior charge separation efficiency and stronger adsorption capacity for NO and O2 molecules, promoting the formation of reactive oxygen species. These results indicated that the best-performing sample, ZATC15, demonstrated an impressive NO removal efficiency of 65.43 %. However, the selectivity rate of NO2 was only 4.78 %, much lower compared to the NO2 selectivity rates of pure ZnAl-LDH (48.17 %) and TiO2@C (72.46 %). The intermediate and final products, the generation pathways of active free radicals (h+ and •O2-) and the mechanism behind the profound oxidation of NO were elucidated based on in-situ Fourier Transform Infrared Spectroscopy (in-situ FT-IR), Electron spin resonance (ESR), and capture experiment. This investigation will offer valuable insights for modifying LDH in order to effectively remove ppb-level NO through photocatalysis.

Engineering of Graphitic Carbon Nitride (g-C3N4) Based Photocatalysts for Atmospheric Protection: Modification Strategies, Recent Progress, and Application Challenges

Graphitic carbon nitride (g-C3N4) is a prominent photocatalyst that has attracted substantial interest in the field of photocatalytic environmental remediation due to the low cost of fabrication, robust chemical structure, adaptable and tunable energy bandgaps, superior photoelectrochemical properties, cost-effective feedstocks, and distinctive framework. Nonetheless, the practical application of bulk g-C3N4 in the photocatalysis field is limited by the fast recombination of photogenerated e--h+ pairs, insufficient surface-active sites, and restricted redox capacity. Consequently, a great deal of research has been devoted to solving these scientific challenges for large-scale applications. This review concisely presents the latest advancements in g-C3N4-based photocatalyst modification strategies, and offers a comprehensive analysis of the benefits and preparation techniques for each strategy. It aims to articulate the complex relationship between theory, microstructure, and activities of g-C3N4-based photocatalysts for atmospheric protection. Finally, both the challenges and opportunities for the development of g-C3N4-based photocatalysts are highlighted. It is highly believed that this special review will provide new insight into the synthesis, modification, and broadening of g-C3N4-based photocatalysts for atmospheric protection.

Enhanced photocatalytic ammonia oxidation over WO3@TiO2 heterostructures by constructing an interfacial electric field

WO3 nanorods and xWO3@TiO2 (WO3/TiO2 mass ratio (x) = 1-5) photocatalysts were synthesized using the hydrothermal and sol-gel methods, respectively. The photocatalytic activities of xWO3@TiO2 for NH3 oxidation first increased and then decreased with a rise in TiO2 content. Among them, the heterostructured 3WO3@TiO2 photocatalyst showed the highest NH3 conversion (58 %) under the simulated sunlight irradiation, which was about two times higher than those of WO3 and TiO2. Furthermore, the smallest amounts of by-products (i.e., NO and NO2) were produced over 3WO3@TiO2. The enhancement in photocatalytic performance (i.e., NH3 conversion and N2 selectivity) of 3WO3@TiO2 was mainly attributed to the formed interfacial electric field between WO3 and TiO2, which promoted efficient separation and transfer of photogenerated charge carriers. Based on the results of reactive species trapping and active radical detection, photocatalytic oxidation of NH3 over 3WO3@TiO2 was governed by the photogenerated holes and superoxide radicals. This work combines two strategies of morphological regulation and interfacial electric field construction to simultaneously improve light utilization and photogenerated charge separation efficiency, which promotes the development of full-spectrum photocatalysts for the removal of ammonia.