Environmental Functional Materials最新文献

Single-atom catalysts (SACs), consisting of metal single atoms and supporting materials, have shown remarkable potential due to their ultrahigh catalytic performances, maximum atomic utilization and environmental friendliness. More recently, SACs have become ideal catalyst materials and have been extensively applied in water treatment. This review summarizes the classification of advanced oxidation processes (AOPs, e.g., photocatalysis, electrocatalysis, Fenton-like reactions, persulfate oxidation and multi-technology coupling reaction) for the degradation of organic pollutants in water on SACs. The corresponding mechanisms for the removal of organic pollutants over SACs in the above technologies are also discussed. Distinguished from traditional nanoparticles and nanoclusters, the unique electronic properties of single metal atoms and the formation of covalent bands between metallic and nonmetallic atom promote the rapid generation of reactive oxygen species (SO₄^•-, O₂^•-, •OH and ¹O₂), which endow SACs with excellent removal efficiency of organic pollutants. Finally, the opportunities and challenges of SACs applied in practical water treatment are proposed.

Metal–organic frameworks (MOFs) containing two different inorganic metal nodes (known as bimetallic MOFs) could exhibit enhanced CO₂ adsorption compared to their monometallic counterparts. Herein, a series of bimetallic NiCo-MOF-74 synthesized by microwave-assisted method were investigated for CO₂ adsorption. It was revealed that narrow micropore channel with open metal site (OMS) of the bimetallic NiCo-MOF-74 influence CO₂ binding affinity and CO₂/N₂ adsorption. The CO₂ uptake of Ni₁Co₁-MOF-74 at 0 ​°C and 1 ​bar (100 ​kPa) was 8.30 ​mmol ​g⁻¹ which is higher than those of Ni-MOF-74 (3.99 ​mmol ​g⁻¹), Ni₆Co₁-MOF-74 (3.62 ​mmol ​g⁻¹), Ni₁Co₆-MOF-74 (6.40 ​mmol ​g⁻¹) and Co-MOF-74 (5.03 ​mmol ​g⁻¹). While this could be related to the high specific surface area of Ni₁Co₁-MOF-74, Ni₁CO₂-MOF-74 with relatively low specific surface areas still shows good CO₂ adsorption capacity up to 5.70 ​mmol/g, which is higher than those of adsorbents Ni-MOF-74, Ni₆Co₁-MOF-74 and Co-MOF-74, indicating that adsorption performance mainly relies on coordinated metals. Ni₁Co₁-MOF-74 showed remarkable recyclability performance, ranking selectivity of CO₂/N₂ reach up to 34, and suitable isosteric heat (31–23 ​kJ ​mol⁻¹), manifesting a great probability for industrial CO₂ capture. As revealed, incorporated Ni²⁺/Co²⁺ nodes within Ni₁Co₁-MOF-74, which are acting as active and open sites for CO₂ capture, led to the synergetic effects comprising of micropores as well as dense dual-metal sites.

Zeolite imidazole framework-8 (ZIF-8) is a promising template to obtain porous nanocarbons. In this study, microporous nitrogen-doped nanocarbons from the carbonization of ZIF-8 (ZCN) was prepared as an efficient metal-free catalyst to improve several micropollutants degradation in Fe(III)/H₂O₂ process. The sulfamethoxazole (SMX) ratio was increased from 20% to 100% with the addition of ZCN (50 ​mg/L) in Fe(III)/H₂O₂ within 20 ​min, and the working pH was endowed. The direct reduction for Fe(III) resulting from carbonyl on ZCN's surface was revealed. Hydroxyl radical (•OH) was determined to be the main reactive species, and the evolution of different Fe species during the reaction was discussed by monitoring the mass balance of Fe species. We found that part of the iron was bound to the surface of ZCN during the reaction. Additionally, the dissociative Fe was captured by ZCN to form Fe-N_x bonds. Surface-bound Fe with a lower energy barrier was more likely to react with H₂O₂ to generate Fe(II). Our work revealed that in addition to the direct reduction by ZCN, another catalytic reduction pathway for the sustainable conversion of Fe(III) to Fe(II) in the ZCN/Fe(III)/H₂O₂ process was operative.

Electrocatalytic reduction of CO₂ is important for mitigating global warming and energy crisis, and the key to an economical and promising CO₂ conversion technology lies in the development of catalysts with high catalytic activity. Here, we report a N-doped carbon-based bimetallic single-atom catalyst (Fe/Mn–N–C) to improve the selectivity of electrocatalytic reduction of CO₂ products by combining with highly active iron-manganese bimetals. At the carbonation temperature of 800 ​°C and the Fe/Mn mass ratio of 1:2 in the precursor, the catalyst Fe/Mn–N–C was able to achieve a Faraday efficiency (FE) of 94% for CO in 0.1 ​M KHCO₃ electrolyte at an overpotential of −0.5 ​V (RHE), which was much higher than that of the Fe–N–C (40%), Mn–N–C (25%), and N–C (25%). And after 12 ​h of continuous catalysis, the FECO was still maintained at more than 80%, demonstrating the good stability of the Fe/Mn–N–C. X-ray absorption spectroscopy (XAS) results confirmed the diatomic dispersed M_xN_y active centers embedded in the exposed substrate of the carbon surface and their dispersion was confirmed by high angle angular dark field-scanning transmission electron microscopy (HAADF-STEM) with atomic resolution. Density functional theory (DFT) calculations showed that the reaction potential for COOH∗ formation and CO desorption was reduced by the synergistic effect of the adjacent Fe–Mn centers. This work provides a great possibility for the preparation of bimetallic single atom catalysts for efficient catalytic conversion of CO₂.

Due to its unique physical and chemical properties, metal sulfide has been proven to be a promising ideal candidate for metal oxide catalysts and has been widely used in many catalytic fields. In recent years, advanced oxidation processes (AOPs), especially those based on metal sulfides, have been recognized as one of the most effective techniques for controlling water pollution due to their superior catalytic performance and stability. However, there is a lack of systematic summary and elaboration of the reported works on metal sulfide catalysts. This work reviews the synthesis, characterization and application of metal sulfide in AOPs for water decontamination. In addition, we further summarized the catalytic oxidation mechanisms of different metal sulfide-based AOPs and combined them with density functional theory (DFT) calculation to clarify the active root of the catalytic reactions of various metal sulfides. Finally, the application of metal sulfide is prospected, including the challenges in large-scale preparation, sulfur hydrochemistry and metal ion leaching, and the stability and reusability of metal sulfide. This review will help guide the future development of metal sulfide and further develop efficient and stable metal sulfide-based AOPs to better deal with water pollution.

Nowadays, the increasing discharge of persistent per- and polyfluoroalkyl substances (PFASs) caused serious environmental issues. In addition to advanced oxidation processes (AOPs), advanced reduction processes (ARPs) based on reducing radicals, e.g., hydrated electron and superoxide anions have attracted great attentions as promising methods for remediation of PFASs pollution. This review, based on 128 cited references, provides a critical overview on the performance of different AOPs and ARPs. The unique properties of reactive species, e.g., SO₄^•- and e_aq⁻ and their generation mechanisms in different systems were discussed. Moreover, the efficiencies of different systems were further compared from several aspects, e.g., PFASs decomposition rate, reaction time and energy consumption. More specially, for some model compounds of PFASs, such as perfluorooctanoic acid, perfluorooctane sulfonate and perfluoroalkyl ether carboxylic acids, we systematically discussed their degradation and defluorination pathways in both AOPs and ARPs. The reported literatures showed that the degradation pathways of these PFASs are closely related to their head groups in either AOPs or ARPs. Finally, some key conclusions were summarized, and the implications of the state-of-the-art knowledge on practical PFASs remediation in water treatments were summarized and the future priority research directions were proposed.

Atmospheric water harvesting is a promising strategy to address the water scarcity in islands. In this work, an activated carbon fiber (ACF) templated hybrid water adsorbent ACF-cobalt(II)-ethanolamine (ACF-Co-EA) was fabricated and used to build an ecological farm (Eco-farm) for potential application on tropical coral islands. ACF-Co-EA took the advantage of both the pore structure of ACF and the superabsorbent property of the Co-EA complex, thus, exhibiting superior water harvest capacity over ACF or Co-EA. The equilibrium water adsorption of ACF-Co-EA was 763 ​mg ​g⁻¹ ​at 25 ​°C and 70% RH (typical environment of tropical coral islands). Under 1 ​kW ​m⁻² simulated solar irradiation, the surface temperature of ACF-Co-EA increased rapidly to 50 ​°C within 12 ​min and stabilized at 54 ​°C in 30 ​min because of the superior light absorbance of ACF, which made more than 90% of captured water released. ACF-Co-EA-based Eco-farm could harvest 6.9 ​g ​g⁻¹·day⁻¹ of water to ensure plant growth in the tropical coral islands' environment without any additional energy or water supply. The study provided novel ideas to alleviate the problems of freshwater scarcity and food shortage in the tropical coral islands.

The heterogeneous activation of persulfate-based advanced oxidation processes (persulfate AOPs) has been defined as potential wastewater treatment methods due to their excellent chemical reactivity. However, the reaction mechanisms of these processes are extremely intricate because of the simultaneous participation of many substances from the solid, liquid, and even gas phases. The development of novel active catalysts is hindered due to divergent mechanisms and deficient research techniques. In this review, the up-to-date development of heterogeneous catalyst category, catalytic characteristics, and reaction mechanism are comprehensively discussed. Essentially, the detection of persulfate, the identification of reactive oxygen species, and the evolution and analysis of organic oxidation pathways are reviewed, highlighting the innovation integration experimental/theoretical protocol to reveal the reaction mechanism in a future study. Finally, the limitations and possible breakthrough directions of persulfate AOPs were discussed, including the further study of the internal reaction mechanism in persulfate AOPs, the requirement of reasonable evaluation of the treatment effect, and the feasibility of full-scale application.