Applied Catalysis B: Environmental最新文献

High–performance catalysts are extremely required for controlling NH₃ emission via selective catalytic oxidation (SCO), and the anchoring structural feature of active sites is a key prerequisite for developing them. This study confirms the importance of hydroxyl groups on vacancy–deficient reducible oxides as active groups. On the one hand, spontaneous atomic dispersion of active metal Ir is promoted by the abundant terminal hydroxyl groups. On the other hand, Ir cations anchor on the TiO₂ surface through exchange with H⁺ in Ti–OH groups, and thus occupy the Brönsted acid sites. The adsorption strength of NH₃ is another key factor affecting the reaction rate–determining step, namely NH₃ dehydrogenation, which occurs at a faster rate in the coordinated L–NH₃ rather than the ionic B–NH₄⁺. Meanwhile, the coordinated L–NH₃ significantly avoids the competitive adsorption of water vapor in the NH₃–SCO reaction by reducing the number of hydrogen bonding. The TOF of preferred 0.8Ir/TiO₂ sample is significantly higher than 0.2Ir/TiO₂ sample, although Ir is almost always atomic dispersed. Finally, NH₃ conversion is 85% in a wet circumstance (5% H₂O) at 240 °C (GHSV = 85 000 h^–1), with a N₂ selectivity of up to 65% on 0.8Ir/TiO₂ sample.

To guarantee the efficient and durable operation of oxygen ion/proton-conducting ceramic fuel cells, the cathode materials need to be versatile in terms of high activity, good CO₂ resistance, and matched thermal expansion behavior with electrolyte, etc. In this study, we substituted 10% Nb to the B-site of parent perovskite-BaCo_0.7Fe_0.2Y_0.1O_3-δ, to form a single-phase material with triple conducting (H⁺/O^2-/e^-) capability as a highly ORR-active cathode. The doped BaCo_0.6Fe_0.2Y_0.1Nb_0.1O_3-δ (BCFYN) shows promising ORR activity due to the optimized oxygen vacancy, improved hydration capacity, and accelerated charge transfer kinetics. The reduction of thermal expansion coefficient (TEC) and enhanced CO₂ resistance also facilitate the cathode durability. As a result, the area-specific resistances of BCFYN electrode at 550 °C for oxygen-ion and proton conducting symmetrical cells were only 0.106 and 0.24 Ω cm², respectively. These results indicate that BCFYN is a highly promising cathode material for both SOFCs and PCFCs.

A series of sludge-derived MnO_x catalysts were successfully obtained by a one-step sludge disintegration process using KMnO₄. The obtained S-MnO_x-1.2 catalyst exhibited excellent activity and superior water resistance under industrial flue gas conditions (5 vol% H₂O, 40–80 ℃, 300,000–600,000 mL/(g·h) of GHSV). β‐MnOOH was the predominant component generated on the sludge surface by a redox reaction between KMnO₄ and organic matter. The superior ozone decomposition performance was mainly ascribed to its large surface area, plentiful oxygen vacancies and interlayer hydroxyl groups. There were two types of surface oxygen vacancies, denoted as ozone-friendly and hydrophilic oxygen vacancies, participated in the ozone elimination process. Surface hydroxyl groups physically adsorbed abundant water molecules and hindered the chemisorption of water on ozone-friendly oxygen vacancies, thereby increasing the water resistance of the catalyst. The present work produced a potential catalyst in favor of ozone elimination, and promoted the high value-added utilization of waste sludge.

The photocatalytic activity for CO₂ reduction of a series of Ni-substituted polyoxometalates (POMs) differing in nuclearity, shape and size, has been investigated under visible light irradiation, with [Ru(bpy)₃]²⁺ (bpy = 2,2′-bipyridine) as photosensitizer and triethanolamine as sacrificial donor. The tetrabutylammonium salt of the Ni₄ tetranuclear species was found to exhibit the highest CO production and its stability under photocatalytic conditions was demonstrated. The catalytic performance was significantly lower for the alkaline salt due to the separation of the POM from its counter-ions occurring only for the tetrabutylammonium salt. Photophysical experiments evidenced a bimolecular electron transfer from the reduced photosensitizer [Ru(bpy)₃]⁺ to the Ni₄ POM, the former arising from the reductive quenching of the [Ru(bpy)₃]²⁺ excited state by triethanolamine. This was further supported by DFT calculations, which also showed that the Ni₄ POM accumulates at least two electrons and four protons to carry out the CO₂ reduction catalytic process.

Direct fuel cells fed with liquid carbon-free fuels (borohydride, ammonia-borane, hydrazine) present a number of benefits compared to state-of-the-art proton-exchange membrane fuel cells, among them ease of fuel transportation and distribution, high volumetric energy density, high theoretical cell voltage, and number of transferred electrons n > 2. However, taking full advantage of these benefits requires highly active anodic catalysts, which allow efficient fuel valorization at close-to-equilibrium potentials. This requires understanding the complex mechanisms of the multi-electron fuel oxidation reactions and the main factors affecting reaction rates and product selectivities. This review offers a state-of-the-art understanding of borohydride, ammonia-borane, and hydrazine oxidation on noble metal and noble metal-free catalysts both in half- and in full-cell configuration. Electrochemical data are complemented with coupled physicochemical techniques and numerical calculations to unveil the main intermediates and co-products and the influence of the different experimental factors on the reaction kinetics and mechanisms.

Solar-energy-driven half-reactions coupling is a vital photocatalysis strategy to simultaneously realize low-value organic platform molecules value-added conversion and hydrogen production. It is essential to design photocatalyst with appropriate band structures and efficient spatial separation of photogenerated hole/electron pairs (h⁺/e^-) to drive reduction/oxidation half-reactions, respectively. Herein, chemical-bonded Ni/Cd_0.7Mn_0.3S Schottky junction was constructed via hydrothermal-chemical reduction method for sunlight-driven catalytic selective dehydrogenation oxidization of benzyl alcohol (BA) coupling with hydrogen evolution reaction (HER). The optimal 8% Ni/Cd_0.7Mn_0.3S exhibited excellent BA conversion rate (77%), benzaldehyde (BAD) yield (2.88 mmol·g⁻¹·h⁻¹), selectivity (99%) and HER activity (2.94 mmol·g⁻¹·h⁻¹). The selective oxidation of BA and its para-substituents (-CH₃, -OCH₃, -Br, -NO₂) proceeded a carbon-centred radical mechanism via the cleavage of α_C-H bond. Furthermore, the Ni/Cd_0.7Mn_0.3S exhibits excellent selective oxidation of the other organic platform molecules with benzyl alcohol structure, such as 5-hydroxymethylfurfural (HMF) and vanillyl alcohol (VAL), etc, validating that the chemical-bonded Ni/Cd_0.7Mn_0.3S possess the excellent performance in α_C-H bond activation of benzyl alcohol structure unit. By combining experiment and DFT calculation results, the Ni-S bond formed at Ni/Cd_0.7Mn_0.3S interface can accelerate the directing charge transfer, thus boosting the organic platform molecules selective oxidation coupling with HER.

The oxygen evolution reaction (OER) performance in cation-doped materials often exhibits a volcano-like relationship with dopant concentration. However, the influence of dopant content with its associated local environment on the electronic states of electrocatalysts remains unclear. Herein, V is incorporated into Ni(OH)₂ to study the underlying mechanism. It is revealed that evenly distributed V can effectively perturb the NiO₆ octahedron, leading to strong e_g * band broadening and more electronic states around the Fermi level. This phenomenon significantly enhances the electron transfer from electrocatalysts to external circuits. Conversely, the aggregation of V at higher dopant concentration exerts weaker influence on perturbing the NiO₆ octahedron. As a result of balance between V doping and aggregation, Ni_0.95V_0.05OOH, with the strongest NiO₆ octahedron distortion, effectuating a remarkably low overpotential of 258 mV at 10 mA cm⁻². Furthermore, such a structure-activity relationship is also extended to Fe-doped Ni(OH)₂, affirming the universality of the proposed mechanism.

Catalytic ozonation is a promising bioaerosol control technology, as O₃ is prevalent in atmosphere. However, O₃ at atmosphere concentration has limited oxidation potential and reactive oxygen species (ROSs) production, leading incomplete bioaerosol inactivation. Therefore, a catalytic ozonation system with a manganese dioxide/Ni foam (MN) was prepared for efficient bioaerosol inactivation. The MN exhibited superior activity in catalytic ozonation bioaerosol inactivation, achieving 91.6% inactivation efficiency within 8.07 s at atmospheric concentration (0.1 ppm) of O₃. The inactivation efficiency can be further improved to 99.0% by regulating surface oxygen vacancies (O_V) in MN, which is mainly attributed to abundant O_V of MN that facilitate rapid conversion of O₃ to other ROSs. Meanwhile, the mechanism of rapid bacterial inactivation was also clarified at cellular level, showing that ROSs caused bacterial oxidative stress. This catalytic ozonation strategy would offer more choices to design efficient O₃ catalysts for bioaerosol control and public health protection.

Fe single-atom catalysts (SACs) have emerged as a promising alternative to platinum for catalyzing oxygen reduction reactions (ORR). Nevertheless, their practical applicability is hindered by insufficient stability caused by structural corrosion during ORR. Here, we developed an effective strategy to optimize and stabilize the Fe SAs (single-atoms) sites by implanting chromium (Cr) atomic clusters (ACs) to address the formidable deactivation issue of the best-performing yet unstable Fe-N-C catalysts. Cr_AC-Fe₁/N-S-C demonstrates an amazing stability with a negligible decline in activity after 100,000 CV cycles, and can maintain 81% of initial current after a continuous 50-hour operation period. Theoretical calculations and experimental evidence substantiate that the integration of Cr ACs not only weakens the binding of OH* to the Fe site, thereby facilitating the ORR process, but also eliminates in situ-generated reactive oxygen species (ROS) and retards Fe ion leaching from active sites, thus stabilizing of the Fe SA sites.

Dynamic p-n junction can drive a drift of electrons from p-type to n-type side, and that of holes in the opposite direction simultaneously, which offers a promising avenue for next generation of advanced photocatalysts. However, construction of dynamic p-n junctions still remains challenging. Herein, dynamic p-n junctions at atomic-scale are constructed by hybridizing two n-type semiconductors, Zn-doped TiO₂ and P-doped C₃N₄. The catalyst (Z_0.01T/CNP-4) gives a stable and remarkable photo-oxidation ability for tetracycline hydrochloride (TCH), giving a much higher space-time yield than previously reported. h⁺, ^•O₂⁻, and ^•OH radicals are main active species for the TCH photo-oxidation. Most importantly, ^•O₂⁻ species react with photo-generated electrons rapidly separated via atomic-level p-n junctions to yield H₂O₂ that further promotes the TCH photo-oxidation process. These findings provide new hints in fabricating more novel dynamic p-n junctions for effectively utilizing both photo-generated electrons and holes in the meanwhile to achieve the full potential of photocatalytic reactions.