Editorial

6 pages, 219 KiB

Open AccessEditorial

Exclusive Papers on Environmentally Friendly Catalysis in China

by Hongxing Dai, Xiang Wang, Yujun Zhu, Haibao Huang and Yunkun Zhao

Catalysts 2023, 13(9), 1272; https://doi.org/10.3390/catal13091272 - 04 Sep 2023

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With the development of modern industries, environmental pollution has become a serious and urgent issue [...] Full article

(This article belongs to the Special Issue Exclusive Papers in Environmentally Friendly Catalysis in China)

Research

Jump to: Editorial, Review

20 pages, 5132 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Catalytic Performance and Reaction Mechanisms of Ethyl Acetate Oxidation over the Au–Pd/TiO₂ Catalysts

by Minming Bao, Yuxi Liu, Jiguang Deng, Lin Jing, Zhiquan Hou, Zhiwei Wang, Lu Wei, Xiaohui Yu and Hongxing Dai

Catalysts 2023, 13(4), 643; https://doi.org/10.3390/catal13040643 - 23 Mar 2023

Cited by 3 | Viewed by 2697

Abstract

The development of efficient and stable catalysts is of great importance for the elimination of volatile organic pollutants (VOCs). In this work, AuPd_x nanoparticles (NPs) were loaded on TiO₂ through the electrostatic adsorption approach to generate the yAuPd_x/TiO [...] Read more.

The development of efficient and stable catalysts is of great importance for the elimination of volatile organic pollutants (VOCs). In this work, AuPd_x nanoparticles (NPs) were loaded on TiO₂ through the electrostatic adsorption approach to generate the yAuPd_x/TiO₂ (i.e., 0.35AuPd_0.46/TiO₂, 0.34AuPd_2.09/TiO₂, and 0.37AuPd_2.72/TiO₂; x and y are Pd/Au molar ratio and AuPd_x loading, respectively; x = 0.46–2.72; and y = 0.34–0.37 wt%) catalysts, and their catalytic activities for the oxidation of ethyl acetate were determined. The results showed that the 0.37AuPd_2.72/TiO₂ sample exhibited the best activity (T_50% = 217 °C and T_90% = 239 °C at SV = 40,000 mL/(g h), E_a = 37 kJ/mol, specific reaction rate at 220 °C = 113.8 µmol/(g_Pd s), and turnover frequency (TOF_{Noble metal}) at 220 °C = 109.7 × 10⁻³ s⁻¹). The high catalytic performance of the 0.37AuPd_2.72/TiO₂ sample was attributed to the good dispersion of AuPd_2.72 NPs, the strong redox ability, the large ethyl acetate adsorption capacity, and the strong interaction between AuPd_x and TiO₂. Acetaldehyde, ethanol, and acetic acid are the main intermediates in the oxidation of ethyl acetate, and the loading of AuPd_x NPs effectively reduces the formation of the toxic by-product acetaldehyde. The oxidation of ethyl acetate over the 0.34AuPd_2.09/TiO₂ sample might occur via the pathway of ethyl acetate → ethanol → acetic acid → acetate → CO₂ and H₂O. We believe that the obtained results may provide a useful idea for the design of bimetallic catalysts under industrial conditions and for understanding the VOCs oxidation mechanisms. Full article

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15 pages, 4559 KiB

Open AccessArticle

Structural Effects of Microcrystalline Cellulose-Derived Carbon Supports on Catalytic Performance of the Pd(OH)₂/C Catalysts for the Hydrogenolytic Debenzylation of Hexanitrohexaazaisowurtzitane Derivatives

by Yuling Wang, Yun Chen, Xinlei Ding, Jianwei Song, Gaixia Wei, Hengwei Dai, Hanyang Wang, Yadong Liu, Guangmei Bai and Wenge Qiu

Catalysts 2023, 13(3), 637; https://doi.org/10.3390/catal13030637 - 22 Mar 2023

Cited by 2 | Viewed by 1410

Abstract

In order to reduce the noble metal palladium dosage in the preparation of CL-20 so as to reduce its production cost, several carbon supports were prepared successfully using the hydrothermal carbonization method in the absence or presence of urea using microcrystalline cellulose (MC) [...] Read more.

In order to reduce the noble metal palladium dosage in the preparation of CL-20 so as to reduce its production cost, several carbon supports were prepared successfully using the hydrothermal carbonization method in the absence or presence of urea using microcrystalline cellulose (MC) as the carbon source, and the corresponding Pd(OH)₂/C catalysts were fabricated using the deposition–precipitation method, which showed high activity in the debenzylation reaction of hexabenzylhexaazaisowurtzitane (HBIW) and tetraacetyldibenzylhexaazaisowurtzitane (TADB). It was found that all the catalysts showed a high efficiency in the debenzylation of HBIW, indicating that the structure of the used carbon supports had a limited impact on the catalyst performance in this reaction. On the contrary, the activities of the catalysts in the debenzylation of TADB were quite different. The results of the nitrogen sorption isotherm measurement (BET), scanning electron microscope (SEM), scanning transmission electron microscopy (STEM), powder X-ray diffraction (XRD), element analysis and temperature programmed desorption (TPD), as well as X-ray photoelectron spectra (XPS) characterizations of the supports and catalysts, showed that the relatively high activity of Pd/HTC in the debenzylation of TADB was related to the high Pd dispersion and novel mesoporous structure, while the further higher activity and stability of Pd/HTC-N_1:1 in the same reaction were related with its high Pd dispersion, high total oxidized Pd species, and high surface pyridinic N contents as well as the eggshell distribution of Pd species on the support. Full article

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14 pages, 3592 KiB

Open AccessArticle

Green and Efficient Acquirement of Unsaturated Ether from Direct and Selective Hydrogenation Coupling Unsaturated Aldehyde with Alcohol by Bi-Functional Al-Ni-P Heterogeneous Catalysts

by Yan Xu, Huiqing Zeng, Dan Zhao, Shuhua Wang, Shunmin Ding and Chao Chen

Catalysts 2023, 13(2), 439; https://doi.org/10.3390/catal13020439 - 18 Feb 2023

Cited by 1 | Viewed by 1265

Abstract

In view of the industrial importance of high-grade unsaturated ether (UE) and the inconvenience of acquiring the compound, herein, a series of low-cost Al-Ni-P catalysts in robust AlPO₄/Ni₂P structure possessing novel bi-functional catalytic features (hydrogenation activation and acid catalysis) [...] Read more.

In view of the industrial importance of high-grade unsaturated ether (UE) and the inconvenience of acquiring the compound, herein, a series of low-cost Al-Ni-P catalysts in robust AlPO₄/Ni₂P structure possessing novel bi-functional catalytic features (hydrogenation activation and acid catalysis) were innovated, and testified to be efficient for directly synthesizing UE with a superior yield up to 97% from the selective hydrogenation coupling carbonyl of unsaturated aldehyde (cinnamaldehyde or citral) with C1–C5 primary or secondary alcohol under 0.1 MPa H₂ and 393 K. The integrated advantages of high efficiency, green manner and convenient operation of the present heterogeneous catalytic system gave the system potential for feasibly harvesting high-grade unsaturated ether in related fine chemical synthesis networks. Full article

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18 pages, 8712 KiB

Open AccessArticle

Methane Dry Reforming over Ni/NiO Supported on Ce-, Zr-, and Al-Modified Y₂O₃ for Hydrogen Production

by Zijian Chen, Lei Mao, Xiuzhong Fang, Xianglan Xu, Junwei Xu and Xiang Wang

Catalysts 2023, 13(2), 430; https://doi.org/10.3390/catal13020430 - 16 Feb 2023

Cited by 2 | Viewed by 1492

Abstract

In this work, Ce, Zr, and Al are used to promote Y₂O₃ as supports for Ni/NiO, with the expectation to obtain more efficient catalysts for DRM reaction. XRD and Raman results have testified that all the three cations have been [...] Read more.

In this work, Ce, Zr, and Al are used to promote Y₂O₃ as supports for Ni/NiO, with the expectation to obtain more efficient catalysts for DRM reaction. XRD and Raman results have testified that all the three cations have been doped into the lattice of Y₂O₃ to form a solid solution structure, thus obtaining supports with decreased crystallinity and improved surface areas. As a result, all the modified catalysts display evidently improved reaction performance. The Ni–support interaction of the modified catalysts is enhanced in comparison with the unmodified catalyst, thus having improved Ni dispersion. Moreover, the modified catalysts have improved alkalinity, which is beneficial to activate CO₂ and enhance the activity. In addition, it is found that all the modified catalysts possess a richer amount of surface active oxygen species (O₂^δ− and O₂⁻), which is critical to eliminate carbon depositions. It is believed that the interaction of these factors is responsible for the enhanced DRM performance of the modified catalysts. In situ DRIFTS results have confirmed that the addition of the secondary metals can improve the DRM activity of the catalyst by accelerating the conversion of formate intermediate species. Full article

(This article belongs to the Special Issue Exclusive Papers in Environmentally Friendly Catalysis in China)

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12 pages, 3557 KiB

Open AccessArticle

Development of Quinary Layered Double Hydroxide-Derived High-Entropy Oxides for Toluene Catalytic Removal

by Tianshan Xue, Yiping Wang, Li Yang, Zhe Li, Yanshan Gao and Qiang Wang

Catalysts 2023, 13(1), 119; https://doi.org/10.3390/catal13010119 - 05 Jan 2023

Cited by 2 | Viewed by 1700

Abstract

In this work, a novel method for the preparation of high-entropy oxides (HEO) was successfully developed using multivariate composition layered double hydroxides (LDHs) as precursor. Thermal treatment over 600 °C led to the complete transformation of LDHs to single spinel phase HEOs. The [...] Read more.

In this work, a novel method for the preparation of high-entropy oxides (HEO) was successfully developed using multivariate composition layered double hydroxides (LDHs) as precursor. Thermal treatment over 600 °C led to the complete transformation of LDHs to single spinel phase HEOs. The performance of the obtained HEO catalysts in the removal of volatile organic compounds (VOCs) was studied with the catalytic oxidation of toluene as the probe reaction. The optimized HEO-600 catalyst showed impressive activity and stability over toluene catalytic oxidation, which resulted from the vast quantity of surface oxygen vacancies and the relative variable metal valence. The T₅₀ and T₉₀ values of HEO-600 were 246 and 254 °C, and the T₉₀ value only presented a slight increase to 265 °C after a 10-cycle test. This work developed a simple way to obtain HEO materials and provide technical support for the application of HEO catalysts for VOCs removal. Full article

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19 pages, 6255 KiB

Open AccessArticle

Enhanced Catalytic Performance and Sulfur Dioxide Resistance of Reduced Graphene Oxide-Promoted MnO₂ Nanorods-Supported Pt Nanoparticles for Benzene Oxidation

by Dan Zhang, Qing Ye, Ning Dong, Wenjin Wang, Yang Xiao and Hongxing Dai

Catalysts 2022, 12(11), 1426; https://doi.org/10.3390/catal12111426 - 13 Nov 2022

Cited by 4 | Viewed by 1402

Abstract

The reduced graphene oxide (rGO)-promoted α-MnO₂ nanorods-supported Pt (xPt-yrGO/α-MnO₂, x = 0.93 wt%, y = 0.5, 1.0, and 2.0 wt%) nanocatalysts were prepared using a polyvinyl alcohol (PVA)-protected reduction method. After an appropriate [...] Read more.

The reduced graphene oxide (rGO)-promoted α-MnO₂ nanorods-supported Pt (xPt-yrGO/α-MnO₂, x = 0.93 wt%, y = 0.5, 1.0, and 2.0 wt%) nanocatalysts were prepared using a polyvinyl alcohol (PVA)-protected reduction method. After an appropriate loading of Pt on α-MnO₂, the strong metal–support interaction between Pt and α-MnO₂ was beneficial for an increase in catalytic activity. The simultaneous addition of rGO to α-MnO₂ not only provided a more amount of benzene adsorption sites, but also acted as an electron transfer channel to accelerate charge migration, thus further improving catalytic activity of α-MnO₂. Among all of the catalyst samples, 0.94Pt-1.0rGO/α-MnO₂ showed the best catalytic performance with 90% benzene conversion at 160 °C and a gas hourly space velocity (GHSV) of 60,000 mL/(g h), which was better than that over the other Pt-based catalysts. The results of in situ DRIFTS characterization revealed that phenol, benzoquinone, and carboxylate species were the intermediates and eventually oxidized to CO₂ and H₂O. When sulfur dioxide was present, catalytic activity of α-MnO₂ decreased due to the formation of manganese sulfate that blocked the active sites, while the loading of Pt and rGO hindered the chemisorption of SO₂ and prevented the active sites of the catalyst from being poisoned by SO₂, thus enhancing sulfur resistance of the catalyst. The 0.94Pt-1.0rGO/α-MnO₂ catalyst presented in this work can be considered as a cost-effective and promising catalyst for the oxidative removal of volatile organic compounds. Full article

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14 pages, 4821 KiB

Open AccessArticle

Morphology Effects on Structure-Activity Relationship of Pd/Y-ZrO₂ Catalysts for Methane Oxidation

by Xiujuan Zhang, Tingting Zheng, Jiangli Ma, Chengxiong Wang, Dongxia Yang and Ping Ning

Catalysts 2022, 12(11), 1420; https://doi.org/10.3390/catal12111420 - 12 Nov 2022

Cited by 1 | Viewed by 1197

Abstract

Pd/Y-ZrO₂ catalysts were prepared by Y-ZrO₂ with different morphologies (flower-like, spherical, reticulated, and bulk-specific morphology), which were prepared by hydrothermal synthesis. Activity evaluation and characterization results show that the morphology influences the microstructures of Y-ZrO₂ and the chemical states of [...] Read more.

Pd/Y-ZrO₂ catalysts were prepared by Y-ZrO₂ with different morphologies (flower-like, spherical, reticulated, and bulk-specific morphology), which were prepared by hydrothermal synthesis. Activity evaluation and characterization results show that the morphology influences the microstructures of Y-ZrO₂ and the chemical states of active Pd species, thus affecting the activity of methane oxidation. Bulk Pd/Y-ZrO₂ exhibits the best CH₄ oxidation activity and thermal stability due to the block shape exposed (101) surface, and the single tetragonal phase structure maintained after high-temperature aging. The relatively large-sized Pd particles and Pd⁰ jointly promote the catalytic oxidation of CH₄. Full article

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21 pages, 6364 KiB

Open AccessFeature PaperArticle

PdPt_y/V₂O₅-TiO₂: Highly Active Catalysts with Good Moisture- and Sulfur Dioxide-Resistant Performance in Toluene Oxidation

by Jingjing Sun, Yuxi Liu, Jiguang Deng, Lin Jing, Minming Bao, Qinpei Sun, Linlin Li, Linke Wu, Xiuqing Hao and Hongxing Dai

Catalysts 2022, 12(11), 1302; https://doi.org/10.3390/catal12111302 - 24 Oct 2022

Cited by 9 | Viewed by 1673

Abstract

Catalytic performance and moisture and sulfur dioxide resistance are important for a catalyst used for the oxidation of volatile organic compounds (VOCs). Supported noble metals are active for VOC oxidation, but they are easily deactivated by water and sulfur dioxide. Hence, it is [...] Read more.

Catalytic performance and moisture and sulfur dioxide resistance are important for a catalyst used for the oxidation of volatile organic compounds (VOCs). Supported noble metals are active for VOC oxidation, but they are easily deactivated by water and sulfur dioxide. Hence, it is highly desired to develop a catalyst with high performance and good moisture and sulfur dioxide resistance in the oxidation of VOCs. In this work, we first adopted the hydrothermal method to synthesize a V₂O₅-TiO₂ composite support, and then employed the polyvinyl alcohol (PVA)-protecting NaBH₄ reduction strategy to fabricate xPdPt_y/V₂O₅-TiO₂ catalysts (x and y are the PdPt_y loading (0.41, 0.46, and 0.49 wt%) and Pt/Pd molar ratio (2.10, 0.85, and 0.44), respectively; the corresponding catalysts are denoted as 0.46PdPt_2.10/V₂O₅-TiO₂, 0.41PdPt_0.85/V₂O₅-TiO₂, and 0.49PdPt_0.44/V₂O₅-TiO₂). Among all the samples, 0.46PdPt_2.10/V₂O₅-TiO₂ exhibited the best catalytic activity for toluene oxidation (T_50% = 220 °C and T_90% = 245 °C at a space velocity of 40,000 mL/(g h), apparent activation energy (E_a) = 45 kJ/mol), specific reaction rate at 230 °C = 98.6 μmol/(g_Pt s), and turnover frequency (TOF_Noble _metal) at 230 °C = 142.2 × 10⁻³ s⁻¹. The good catalytic performance of 0.46PdPt_2.10/V₂O₅-TiO₂ was associated with its well-dispersed PdPt_2.10 nanoparticles, high adsorbed oxygen species concentration, good redox ability, large toluene adsorption capacity, and strong interaction between PdPt_y and V₂O₅-TiO₂. No significant changes in toluene conversion were detected when 5.0 vol% H₂O or 50 ppm SO₂ was introduced to the reaction system. According to the characterization results, we can realize that vanadium is the main site for SO₂ adsorption while PdO is the secondary site for SO₂ adsorption, which protects the active Pt site from being poisoned by SO₂, thus making the 0.46PdPt_2.10/V₂O₅TiO₂ catalyst show good sulfur dioxide resistance. Full article

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9 pages, 2199 KiB

Open AccessArticle

Synthesis of Durian-like TiO₂@CdS Core-Shell Structure and Study on H₂ Generation Properties

by Dongping Li, Zeheng Chen, Xin Wang, Zhenhong Zhong, Chunjun Chen and Mengling Wu

Catalysts 2022, 12(10), 1211; https://doi.org/10.3390/catal12101211 - 11 Oct 2022

Cited by 2 | Viewed by 1341

Abstract

Novel durian-like TiO₂@CdS core-shell particles were synthesized through a solvothermal method in ethylenediamine solution and the obtained nanocomposites were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and transmission electron microscopic (TEM) techniques. It can be seen from the [...] Read more.

Novel durian-like TiO₂@CdS core-shell particles were synthesized through a solvothermal method in ethylenediamine solution and the obtained nanocomposites were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and transmission electron microscopic (TEM) techniques. It can be seen from the characterization that the synthesized core-shell structured particles show uniform size. The possible formation mechanism of TiO₂@CdS core-shell particles is also presented schematically. CdS grows on the TiO₂ surface in the form of nanorods, turning the TiO₂@CdS composite particles into durian-like structures. The durian-like TiO₂@CdS core-shell particles prepared in the experiment can overcome the disadvantages of TiO₂ and CdS, respectively. They not only produce a higher yield of H₂ than pure TiO₂; the durian-like TiO₂@CdS nanostructures formed at 180 °C for 16 h produced 2.5 times as much H₂ as did TiO₂, also showing enhanced stability as compared with pure CdS. Full article

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9 pages, 2112 KiB

Open AccessCommunication

Nitrogen-Doped Pitch-Based Activated Carbon Fibers with Multi-Dimensional Metal Nanoparticle Distribution for the Effective Removal of NO

by Shengkai Chang, Zhuo Han, Jianxiao Yang, Xuli Chen, Jiahao Liu, Yue Liu and Jun Li

Catalysts 2022, 12(10), 1192; https://doi.org/10.3390/catal12101192 - 08 Oct 2022

Cited by 4 | Viewed by 1731

Abstract

The design of catalytic materials for NO_X removal by the selective catalytic reduction with NH₃ (NH₃-SCR) has been a focus of research in the field of waste gas treatment. In this work, pitch-based activated carbon fibers (ACFs) were impregnated [...] Read more.

The design of catalytic materials for NO_X removal by the selective catalytic reduction with NH₃ (NH₃-SCR) has been a focus of research in the field of waste gas treatment. In this work, pitch-based activated carbon fibers (ACFs) were impregnated with copper nitrate and cerium nitrate, and then the ACFs that were loaded with bimetallic nanoparticles (ACF@Cu/Ce) were obtained after the pyrolyzation and reduction were performed. Moreover, the ACF@Cu/Ce were furtherly treated through the chemical vapor deposition and NH₃ activation, through which the N-doped carbon nanofibers (N-CNFs) were grown on the surface of the ACFs. Thus, the catalytic material with a multi-dimensional metal nanoparticle distribution and nitrogen-rich network structure, namely the N-CNF/ACF@Cu/Ce, was constructed. In the NH₃-SCR reaction, the NO conversion of the N-CNF/ACF@Cu/Ce could be maintained at about 72~81% in a wide temperature window of 295~495 °C, which enabled the N-CNF/ACF@Cu/Ce to meet the requirements of the practical applications. Full article

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13 pages, 3922 KiB

Open AccessArticle

Effect of Morphology-Dependent Oxygen Vacancies of CeO₂ on the Catalytic Oxidation of Toluene

by Ahmed Ismail, Muhammad Zahid, Boren Hu, Adnan Khan, Nauman Ali and Yujun Zhu

Catalysts 2022, 12(9), 1034; https://doi.org/10.3390/catal12091034 - 11 Sep 2022

Cited by 8 | Viewed by 1722

Abstract

Catalytic oxidation is regarded as an effective, economical, and practical approach to remove volatile organic compounds such as important air pollutants. CeO₂ catalysts with different morphologies exhibit different oxygen vacancies content, which plays a vital role in oxidation reaction. Herein, three distinct [...] Read more.

Catalytic oxidation is regarded as an effective, economical, and practical approach to remove volatile organic compounds such as important air pollutants. CeO₂ catalysts with different morphologies exhibit different oxygen vacancies content, which plays a vital role in oxidation reaction. Herein, three distinct morphologies of CeO₂ i.e., shuttle (CeO₂ (S)), nanorod (CeO₂ (R)), and nanoparticle (CeO₂ (P)), were successfully fabricated by the SEM and TEM results, and investigated for toluene catalytic oxidation. The various characterizations showed that the CeO₂ (S) catalyst exhibited a larger surface area along with higher surface oxygen vacancies in contrast to CeO₂ (R) and CeO₂ (P), which is responsible for its excellent toluene catalytic oxidation. The 90% toluene conversion temperature at 225 °C over CeO₂ (S) was less than that over CeO₂ (R) (283 °C) and CeO₂ (P) (360 °C). In addition, CeO₂ (S) showed a greater reaction rate (14.37 × 10⁻² μmol∙g⁻¹∙s⁻¹), TOF_ov (4.8 × 10⁻⁴∙s⁻¹) at 190 °C and lower activation energy value (67.4 kJ/mol). Furthermore, the CeO₂ (S) also displayed good recyclability, long-term activity stability, and good tolerance to water. As a result, CeO₂ (S) is considered a good candidate to remove toluene. Full article

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15 pages, 7252 KiB

Open AccessArticle

Solid-State Synthesis of ZnO/ZnS Photocatalyst with Efficient Organic Pollutant Degradation Performance

by Xuekun Jin, Jianjun Chen, Fengjuan Chen, Haiming Duan, Ziyu Wang and Junhua Li

Catalysts 2022, 12(9), 981; https://doi.org/10.3390/catal12090981 - 31 Aug 2022

Cited by 9 | Viewed by 1736

Abstract

To improve the separation efficiency of photogenerated carriers in ZnS, constructing a ZnS-based heterostructure with ZnO is assessed to be an efficient strategy, and a ZnO/ZnS photocatalyst was prepared by a solid-phase approach, and the structure and morphology were systematically studied. The ZnO/ZnS [...] Read more.

To improve the separation efficiency of photogenerated carriers in ZnS, constructing a ZnS-based heterostructure with ZnO is assessed to be an efficient strategy, and a ZnO/ZnS photocatalyst was prepared by a solid-phase approach, and the structure and morphology were systematically studied. The ZnO/ZnS photocatalyst showed excellent photocatalytic properties on methyl orange, rhodamine B and tetracycline under UV light irradiation, indicating that the photocatalyst exhibited efficient broad-spectrum photocatalytic performance. Compared with ZnS, the degradation rates of ZnO/ZnS photocatalysts for methyl orange, rhodamine B and tetracycline under UV light increased from 21%, 9% and 32% to 96%, 94% and 93%, respectively, higher than the reported ZnO/ZnS composites synthesized by a novel wet chemical route, attributing to the improvement of light absorption ability and the effective separation of carriers. In addition, the influence of the sacrificial agent on the reaction system was investigated, and the synergistic mechanism of ZnO and ZnS in the catalytic process was analyzed according to the fluorescence spectra, photocurrent and first-principles calculation results, and a possible catalytic mechanism was put forward. Full article

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Review

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11 pages, 2108 KiB

Open AccessReview

Research Progress on Sulfur Deactivation and Regeneration over Cu-CHA Zeolite Catalyst

by Jiangli Ma, Shiying Chang, Fei Yu, Huilong Lai and Yunkun Zhao

Catalysts 2022, 12(12), 1499; https://doi.org/10.3390/catal12121499 - 23 Nov 2022

Cited by 3 | Viewed by 1364

Abstract

Benefiting from the exceptional selective catalytic reduction of NOx with ammonia (NH₃-SCR) activity, excellent N₂ selectivity, and superior hydrothermal durability, the Cu²⁺-exchanged zeolite catalyst with a chabazite structure (Cu-CHA) has been considered the predominant SCR catalyst in nitrogen [...] Read more.

Benefiting from the exceptional selective catalytic reduction of NOx with ammonia (NH₃-SCR) activity, excellent N₂ selectivity, and superior hydrothermal durability, the Cu²⁺-exchanged zeolite catalyst with a chabazite structure (Cu-CHA) has been considered the predominant SCR catalyst in nitrogen oxide (NOx) abatement. However, sulfur poisoning remains one of the most significant deterrents to the catalyst in real applications. This review summarizes the NH₃-SCR reaction mechanism on Cu-CHA, including the active sites and the nature of hydrothermal aging resistance. On the basis of the NH₃-SCR reaction mechanism, the review gives a comprehensive summary of sulfate species, sulfate loading, emitted gaseous composition, and the impact of exposure temperature/time on Cu-CHA. The nature of the regeneration of sulfated catalysts is also covered in this review. The review gives a valuable summary of new insights into the matching between the design of NH₃-SCR activity and sulfur resistance, highlighting the opportunities and challenges presented by Cu-CHA. Guidance for future sulfur poisoning diagnosis, effective regeneration strategies, and a design for an efficient catalyst for the aftertreatment system (ATS) are proposed to minimize the deterioration of NOx abatement in the future. Finally, we call for more attention to be paid to the effects of PO₄^3- and metal co-cations with sulfur in the ATS. Full article

(This article belongs to the Special Issue Exclusive Papers in Environmentally Friendly Catalysis in China)

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18 pages, 1846 KiB

Open AccessReview

Single-Atom Catalysts: Preparation and Applications in Environmental Catalysis

by Xiaohui Yu, Jiguang Deng, Yuxi Liu, Lin Jing, Zhiquan Hou, Wenbo Pei and Hongxing Dai

Catalysts 2022, 12(10), 1239; https://doi.org/10.3390/catal12101239 - 14 Oct 2022

Cited by 9 | Viewed by 3017

Abstract

Due to the expensive price and the low reserve of noble metals in nature, much attention has been paid to single-atom catalysts (SACs)—especially single-atom noble metal catalysts—owing to their maximum atomic utilization and dispersion. The emergence of SACs greatly decreases the amount of [...] Read more.

Due to the expensive price and the low reserve of noble metals in nature, much attention has been paid to single-atom catalysts (SACs)—especially single-atom noble metal catalysts—owing to their maximum atomic utilization and dispersion. The emergence of SACs greatly decreases the amount of precious metals, improves the catalytic activity, and makes the catalytic process progressively economic and sustainable. However, the most remarkable challenge is the active sites and their stability against migration and aggregation under practical conditions. This review article summarizes the preparation strategies of SACs and their catalytic applications for the oxidation of methane, carbon monoxide, and volatile organic compounds (VOCs) and the reduction of nitrogen oxides. Furthermore, the perspectives and challenges of SACs in future research and practical applications are proposed. It is envisioned that the results summarized in this review will stimulate the interest of more researchers in developing SACs that are effective in catalyzing the reactions related to the environmental pollution control. Full article

(This article belongs to the Special Issue Exclusive Papers in Environmentally Friendly Catalysis in China)

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