Applied Catalysis B: Environmental最新文献

The effective activation of peroxymonosulfate (PMS) by polymer carbon nitride (PCN) is hampered by the unpredictable movement and rapid recombination of photocarriers. In this study, niacin served as a beneficial modifier to help constructed the directional electron transfer pathway from the center to the edge in the synthesized PCN catalyst (UCNNA) for efficient PMS activation. The UCNNA/PMS/vis shows the highest kinetic constants (0.050 min⁻¹), which is 2.9-fold increase over the PCN/PMS/vis. The experiments and theoretical calculations indicated that niacin as electron acceptor group prevents the recombination of photocarriers in-plane. Simultaneously, niacin can serve as PMS adsorption site, further facilitating electron transfer and the ¹O₂ generation. Mass spectrometry analysis and Fukui index calculations confirm the priority of lateral chain oxidation (¹O₂ attack site) during atrazine degradation. These results provide new insights into rational design of metal-free catalysts/PMS/vis system, as well as providing guidance and theoretical support for atrazine degradation mechanisms.

Ni, N-doped carbon materials (Ni–N–C) are prosperous candidates for the electrochemical CO₂ reduction reaction (CO₂RR) due to their outstanding activity and selectivity. However, the role of the coexisting uncoordinated N-doped sites and Ni nanoparticles (Ni-NPs) in overall CO₂RR has been overlooked in prior studies. To address this gap, a low temperature synthesis method developed for Ni-NP-encapsulated Ni–N–C nanotube (Ni-NCNT) catalysts with atomically dispersed Ni–N₄ and abundant uncoordinated N-doped sites, where Ni-NPs increase the electron density on Ni–N–C nanotube through carbon network and synergistically enhances the CO₂RR activity. The systematic analysis reveals the cooperative role of Ni-NPs and uncoordinated N-doped sites in altering the electronic structure of Ni–N₄ sites. The results of control experimental studies confirm the synergistic interaction of uncoordinated N-doped sites boost the CO₂RR activity of Ni–N₄ sites. Additionally, density functional theory calculations show that the strong interaction between the Ni-NPs and Ni–N–C did not affect the electronic structures of the Ni–N₄ centers, but rather alter the electronic structure of uncoordinated pyridinic-N sites. This variation led to decreased the energy barriers of rate-limiting steps of COOH* formation on Ni–N₄ and N-doped sites, resulting in excellent CO₂RR performance.

Covalent organic frameworks (COFs) have been acknowledged as a potential platform for heterogeneous photoredox cross-coupling due to their excellent chemical stability, admirable controllability, and extremely prominent surface area. However, synthesizing COFs with bidentate ligand units and utilizing active sites remain a grand challenge. Herein, we report a promising new family of 2,6-pyridinedicarboxaldehyde-bis-(p-aminophenylimine)-based two-dimensional (2D) COFs (PP-COF) using an amine monomer and classic tri-aldehydes. On this basis, dispersed Ni single-atom sites were immobilized on three-types imine-based bi-coordinated 2D COFs (Ni SAS-PP-COF) as heterogeneous dual photoredox catalysts for photo/Ni dual-catalyzed C–N cross-coupling between aryl bromides and alkyl/sulfo amines. Under solar energy irradiation, PP-COF could absorb light to generate electrons and holes, then the photogenerated electrons are transferred to Ni sites to reduce divalent nickel to monovalent nickel. Monovalent nickel is necessary to drive the nickel catalytic cycle. Due to the increased charge separation and abundant active sites, the state-of-the-art Ni SAS-PP-COFs catalyst achieves excellent catalytic performance in comparison of pristine PP-COF. The heterogeneous Ni SAS-PP-COF catalytic system not only confirms the prospect of COFs as potential photoredox/transition-metal dual catalysts, but also provides in-depth insights into the synthesis of functional COFs toward practical metallaphotocatalytic application.

The oxygen evolution reaction (OER) is regarded as a critical component in the water splitting system. Creating vacancies, increasing active surface area, and optimizing electronic structure would improve electrocatalytic performance. Herein, a facile electrochemical reduction method is used to generate sulfur vacancies in nickel iron sulfide (NiFe-S) with a large geometry area of 15 × 16 cm², which is synthesized using an electrodeposition process assisted with the ion exchange (IOE) method. The X-ray absorption spectroscopies (XAS) are applied for atomic-level structural analysis, verifying that electrochemical desulfurization generates abundant S vacancies. The NiFe-S with abundant sulfur vacancies (NiFe-S-V_s) exhibits a low overpotential (252 mV at 100 mA cm⁻²), and long stability for 260 h at 500 mA cm⁻². More importantly, the NiFe-S-V_s catalyst also delivers a small overpotential (235 mV at 1000 mA cm⁻²) and high alkaline tolerance (140 h at 500 mA cm⁻²) in 6 M KOH at 60 °C), implying a potentially significant industrial application prospect. Finally, theory calculation further illustrates the high performance of as-prepared vacancies-rich catalyst.

The electrocatalytic nitrogen reduction reaction (ENRR) offers a sustainable and cost-effective strategy for ammonia (NH₃) synthesis. However, the broad applicability of ENRR is currently limited by challenges in the adsorption and activation of N₂ at the catalyst interface. Addressing these issues, we have developed an innovative approach that constructs an interfacial electric field, coupled with an atomically local electric field induced by W-N bonds. This coupled interfacial-local electric field effectively elevates the d_z² occupancy of W active sites, thereby significantly enhancing the adsorption and activation of N₂. This work provides profound insights into the relationship between the interfacial-local electric field and the efficient execution of ENRR, paving the way for future explorations and potential breakthroughs within catalytic field.

Alcohol and water photooxidation reactions are employed in concert with optical spectroscopy analyses to demonstrate the occurrence of multiple and distinctive charge-transfer (CT) mechanisms in the environmental photocatalyst MIL-125(Ti). The contribution of ligand-to-metal CT (LMCT) mechanisms increases at wavelengths lower than 320 nm while that of node oxygen-to-metal CT (OMCT) mechanisms increases at longer wavelengths. The localization of photogenerated holes on different atoms leads to a selective reactivity of the framework depending on the mechanism and, during hydroxylation processes, to its spontaneous transition to the isostructural MIL-125-OH(Ti) and the development of an additional LMCT mechanism with a long-lived emission. Furthermore, a previously unidentified and extrinsic CT mechanism is spectroscopically related to the formation of terephthalate-based oligomers. The coexistence of distinctive CT mechanisms in MIL-125(Ti) implies their critical role in catalyst efficiency, and mastering them proves to be a powerful and simple strategy to produce the valuable MIL-125-OH(Ti).

The generation of singlet oxygen (¹O₂) based on photocatalytic activation O₂ is considered to have important application prospects in purifying refractory organic pollutants in water. However, the uncertain dual pathway transformation of activated O₂ severely limits the generation of ¹O₂. In this work, we show a robust BiOCl with dual defects (adjacent I-substitution defect and Cl vacancy) in halogen layer for the selective activation of O₂ to generate ¹O₂. Combining experiments and theoretical calculations, we confirm that dual defects are beneficial in optimizing band structures, improving carrier separation efficiency, and promoting O₂ adsorption and activation. More importantly, it is confirmed that dual defects can directionally convert O₂ into ¹O₂ by increasing the thermodynamic conversion energy barrier of non-¹O₂ conversion pathways and serving as a necessary site for ¹O₂ generation with dual functions of oxidation and reduction. Applying dual defect modified BiOCl to the removal of refractory aromatic pollutants in water, it is found that it has efficient and stable photocatalytic degradation efficiency and broad environmental adaptability. This work not only provides in-depth insights into the mechanism of photocatalytic activation of O₂ to selective produce ¹O₂, but also lays the foundation for further development of highly active photocatalysts for environmental remediation and energy conversion.

Artificial H₂O₂ photosynthesis, one of the brightest strategies toward H₂O₂ production, is always restricted by the intrinsically charge migration behaviors and redox kinetics of photocatalysts. Herein, different precursors of carbon nitride (C₃N₄) with urea and melamine (Mel) are synthesized, where C₃N₄-Urea has more delocalized electrons due to its smaller size and thickness, compared with C₃N₄-Mel. Under simulated sunlight irradiation, these abundant delocalized electrons rapid reduce oxygen into H₂O₂, with the rate of 4.9 mmol g⁻¹ h⁻¹ and 2e^- transfer selectivity of 98%. In addition, a self-photo-Fenton reaction system is constructed to remove oxytetracycline (OTC) pollutants and its antibiotic resistant genes (ARG) in water, with the degradation rate of 3.75 min⁻¹ for OTC and 0.08 min⁻¹ for tetC ARG. The current approach by modulating the precursors of C₃N₄ to boost the local electron delocalization offers a promising route for improving the efficiency of artificial H₂O₂ photosynthesis.

Visible-light-driven photocatalytic hydrogen evolution is considered as one of the most useful approaches to produce renewable fuels from abundant resources. Indium oxide (In₂O₃) has attracted much attention in the field of solar hydrogen production due to its moderate band gap, which can be driven by visible light easily. However, the efficiency of hydrogen evolution reaction (HER) of In₂O₃ is currently unsatisfactory. To enhance the HER efficiency of In₂O₃, herein, sandwich-structured In₂O₃/ZnIn₂S₄ heterostructure was precisely constructed via in-situ growth of ZnIn₂S₄ nanosheets on the In₂O₃ hollow fibers. The fabricated In₂O₃/ZnIn₂S₄ heterostructure exhibited a significantly enhanced photocatalytic HER activity of 2.18 mmol/g/h as compared to pure In₂O₃ and ZnIn₂S₄. Such efficient photocatalytic hydrogen production is attributed to the tightly-bound interface between (001) planes of flake ZnIn₂S₄ and (222) planes of In₂O₃. Experimental and theoretical investigation indicates compactly interface enabling efficient charge transfer and separation, which benefited the excellent photocatalytic HER performance.