CERAMICS INTERNATIONAL
·
2023
·
IF 5.2
Junjie Yan,Xiumei Wu,Qidong Liu,Yunping Li,Shu Yu
Silicon oxycarbide (SiOC) coatings were prepared through isothermal chemical vapor co-deposition by using two precursors of hexamethyldisilane (HMDS) and tetraethyl orthosilicate (TEOS). The microstructure, composition and the protectiveness on C/C composite against oxidation of the coatings prepared at temperatures ranging from 1423 K to 1563 K and pressures ranging from 500 Pa to 1200 Pa were investigated, respectively. After oxidation, cracks and defects were formed in the coatings of all conditions due to the volume shrinkage of amorphous SiO 2 crystallization and the mismatch of thermal expansion coefficient (CTE) between SiOC coatings and substrate. The most oxidation-resistant SiOC coating was obtained at 1563 K and 500 Pa, which exhibited the lowest weight loss rate of 4.87 % after 12 h of oxidation at 1673 K in air condition.
研究领域:
材料科学
·
表面工程
✓ 已验证
产品关联
DOI
高影响因子
Journal of Energy Chemistry
·
2024
·
IF 14
Hongqiang Yang,Jianfeng Zheng,Guoyu Wang,Yifei Gao,Yatao Yang,Jia Li,Xiaojin Han,Yan Cui,Zhanggen Huang
Photoelectrocatalytic coupling CO 2 and volatile organic compounds (VOCs) is a promising green strategy for the synergistic conversion of the two carbon-containing resources to C 2 products. The catalytic efficiency is always at the mercy of chemical inertness of CO 2 and the competitive hydrogen evolution of H 2 O. Herein, a modified g-C 3 N 4 /ZnAl-LDH Z-scheme heterojunction catalyst with dual reaction site was rationally designed and precisely constructed. The Faraday efficiency of ethanol reached 68.67% with a corresponding formation rate of 227.3 μmol g −1 h −1 . As revealed by in-situ characterizations and density functional theory calculations, CO 2 and HCHO were absorbed at Zn site and N site, respectively. Then, *CO generated from CO 2 and HCHO was converted to *CH 3 O and *CHO on the dual-active-site heterojunction. The detailed reaction mechanism experiments indicated that C–C coupling only occurred between *CO and *CH 3 O in electrocatalysis process. Apart from the “*CO + *CH 3 O” path, another “*CO + *CHO” coupling path was also detected in photoelectrocatalytic process. The selectivity of ethanol was significantly enhanced due to the synthesis of dual-site catalyst and the dual-path coupling path between CO 2 and HCHO simultaneously driven by light and electricity.
研究领域:
环境科学
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材料科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2025
·
IF 21.1
Xiuzheng Deng,Jiangchuan Liu,Jun Cai,Dan Wang,Huihui Mao,Changhai Liu,Zhongyu Li,Zhenhui Kang,Qian Liang
High production capacity of C 2 products from CO 2 photoreduction remains a significant challenge owing to the difficulty of C-C coupling and weak hydrogenation. Herein, a novel stepwise C-C coupling and hydrogenation mechanism is developed on multisite catalyst to enhance the performance of photocatalytic CO 2 reduction to C 2 products. The active Co cluster, carbon dots (CDs) and Cs 3 Bi 2 Br 9 quantum dots (QDs) are reinforced with robust carbon matrix, which allows to accelerate mass/electron transport and improve stability of catalytic sites, enabling a competitive C 2 H 4 evolution rate of 57.60 μmol g cat −1 h −1 with 67.70 % C 2 H 4 selectivity. In situ experiments coupled with theoretical calculations verify that Co and CDs capture photogenerated electrons from Cs 3 Bi 2 Br 9 to form key intermediate Co-*CO-*CO-CDs. After *CO-*CO coupling on Co site, the proximal CDs provide plenty of protons to conduct continuous hydrogenation toward coupling site until C 2 H 4 is formed. This study paves a novel pathway to regulate C-C coupling and hydrogenation for CO 2 conversion to C 2 hydrocarbons.
研究领域:
催化化学
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环境科学
·
材料科学
·
物理化学
·
能源化学
·
纳米科技
✓ 已验证
产品关联
DOI
高影响因子
COMPOSITES PART B-ENGINEERING
·
2024
·
IF 12.7
Junjie Xu,Wei Sun,Xiang Xiong,Hongbo Zhang
Compared with the traditional C/C composites modified by ultra-high-temperature ceramics (C/C-UHTCs), those modified by metal/medium-entropy ceramics have excellent mechanical properties, thermophysical properties, and long-term ablation resistance. These composites have great potential towards improving the high-temperature resistance and service life of thermal protection systems for spacecraft. In this study, a new type of (Hf 0.5 Zr 0.3 Ti 0.2 )C–W–Cu cermet-modified C/C composites (C/C-(Hf 0.5 Zr 0.3 Ti 0.2 )C–W–Cu) was prepared at 1500 °C. Compared with C/C-UHTCs, the bending strength and fracture toughness of C/C-(Hf 0.5 Zr 0.3 Ti 0.2 )C–W–Cu increased by 70 % and 110 % to 364.25 MPa and 14.64 MPa m 1/2 , respectively. Due to the high thermal conductivity of Cu and W, the thermal conductivity of this new composite was 106 % higher than that of C/C-(Hf 0.5 Zr 0.3 Ti 0.2 )C (44.26 versus 21.53 W/m·K). Under a high heat flow of 4.18 MW/m 2 , this material exhibited very low mass and linear ablation rates (−0.163 mg/s and −0.193 μm/s, respectively). Active and passive protection occur during ablation due to the evaporative cooling of Cu, CuO, and WO 3 as well as a dense outer oxide layer that inhibits oxygen diffusion. The internal oxide layer forms a Hf-Zr-Ti-C-O framework mingled with Ti-rich Ti-Hf-Zr-C-O and an unoxidised W–Cu structure, effectively reducing the osmotic oxygen content. This work provides a new direction for developing thermal protection materials capable of long-term service in ultra-high-temperature environments.
研究领域:
材料科学
·
航空航天工程
✓ 已验证
产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2023
·
IF 22.1
Qingqing Zhang,Yi-Chun Chu,Zhulan Liu,Mei Hong,Weiwei Fang,Xin-Ping Wu,Xue-Qing Gong,Zupeng Chen
Photocatalytic lignin depolymerization emerges as a sustainable and cost-competitive strategy to produce low-molecular-weight aromatic chemicals from renewable resources. Significant efforts have been devoted to engineering C−C bond cleavage photocatalysts with diverse compositional and morphologic characteristics in the past decade. We herein present a facile photocatalytic strategy of promoting C−C bond cleavage in lignin models to achieve high-yield aromatic monomers over triazine-heptazine-based carbon nitride heterojunctions, exceeding the triazine- or heptazine-based counterparts. Mechanistic investigations reveal that the photo-excited electron and hole synergistically trigger the C−C bond cleavage. A combination of experimental results and theoretical calculations confirms that the improved photocatalytic performance is primarily attributed to the accelerated charge carriers separation and migration induced by the built-in electric field at the heterojunction interface, and the facilitated C β -radical generation. These findings highlight the effectiveness of interfacial engineering of intramolecular heterostructures towards the rational promotion of photocatalytic cleavage of C−C bond in lignin models.
研究领域:
材料科学
·
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
Nature Communications
·
2024
·Vol. 15
·期 1
·1-11
·
IF 14.7
Yang Xiaoju,Rong Chao,Zhang Li,Ye Zhenkun,Wei Zhiming,Huang Chengdi,Zhang Qiao,Yuan Qing,Zhai Yueming,Xuan Fu-Zhen,Xu Bingjun,Zhang Bowei,Yang Xuan
Developing in situ/operando spectroscopic techniques with high sensitivity and reproducibility is of great importance for mechanistic investigations of surface-mediated electrochemical reactions. Herein, we report the fabrication of highly ordered rhombic gold nanocube superlattices (GNSs) as substrates for surface-enhanced infrared absorption spectroscopy (SEIRAS) with significantly enhanced SEIRA effect, which can be controlled by manipulating the randomness of GNSs. Finite difference time domain simulations reveal that the electromagnetic effect accounts for the significantly improved spectroscopic vibrations on the GNSs. In situ SEIRAS results show that the vibrations of CO on the Cu 2 O surfaces have been enhanced by 2.4 ± 0.5 and 18.0 ± 1.3 times using GNSs as substrates compared to those on traditional chemically deposited gold films in acidic and neutral electrolytes, respectively. Combined with isotopic labeling experiments, the reaction mechanisms for C-C coupling of CO electroreduction on Cu-based catalysts are revealed using the GNSs substrates.
研究领域:
电化学
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表面科学
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材料科学
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光谱学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
NANOTECHNOLOGY
·
2024
·Vol. 35
·期 49
·495704
·
IF 2.9
Gang Xiao,Zishuai Wang,Yu Jin,Fengping Wang
The selective cleavage of lignin C–C bonds is a highly sought-after process with the goal of obtaining low-molecular-weight aromatic chemicals from renewable resources. However, it remains a challenging task to achieve under mild conditions. Photocatalysis is a potentially promising approach to address this issue, but the development of efficient photocatalysts is still in progress. In this study, we introduce the heterostructured TiO2@g-C3N4 photocatalyst for the development of a visible light photocatalytic procedure for the selective cleavage of lignin C–C bonds under mild conditions. The photocatalyst displays favourable visible light absorption, efficient charge separation efficiency, and promising reusability. A typical β–O–4 dimer model, 2-phenoxy-1-phenylethanol, was effectively (96.0% conversion) and selectively (95.0 selectivity) cleaved under visible light at ambient conditions. This photocatalytic procedure was also effective when subjected to solar irradiation or other lignin dimer models with β–O–4 or β-1 linkages. This reaction occurred through a Cβ-centred radical intermediate and a six-membered transition state with photogenerated holes as the primary active species. The Cα–OH oxidative dehydrogenation of the substrate could also take place but was a relatively minor route. This study provides a new photocatalytic procedure for visible-light-driven lignin valorisation and sheds light on the design of high-performance nanocomposite photocatalysts for C–C bond cleavage.
研究领域:
化学工程
·
材料科学
·
可再生能源
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CERAMICS INTERNATIONAL
·
2024
·
IF 5.1
Junjie Xu,Wei Sun,Xiang Xiong,Hongbo Zhang,Lingkun Yang
Spacecraft thermal protection materials need to survive long-term exposure to oxygen-containing environments at 2400 °C. In this study, a high-density and low-porosity metal-ceramic-modified composite was prepared at a low temperature (1500 °C) in the presence of W and Cu using combined slurry brushing and reactive melt infiltration methods. An investigation of the composite formation mechanism and the effects of W and Cu indicated that W and ZrB 2 were formed via dissolution-precipitation and the external diffusion of C and B, respectively. The low reaction temperature and the metallic phases significantly improved the mechanical properties, thermophysical properties, and long-term ablation behaviours of C/C–ZrC–ZrB 2 –W–Cu. Compared to traditional C/C–ZrC, the flexural strength and fracture toughness of the composite increased by 71.56 % and 90.05 % to 345.95 MPa and 14.52 MPa m 1/2 , respectively, and the thermal conductivity increased by 174.93 % to 59.11 W/m·K. In addition, W and Cu effectively lowered the surface temperature by nearly 250 °C during 300 s ablation, and the mass and line ablation rates decreased to −0.272 mg/s and −0.247 μm/s, respectively.
研究领域:
材料科学
·
航天工程
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2025
·
IF 5.6
Cuiyan Li,Jintao Wang,Haibo Ouyang,Tianzhan Shen,Zihao Chen,Leer Bao,Yanlei Li,Qiaoqiao Wang
s To reduce the cost of C/C-ZrC-SiC composites, an inorganic salt strategy was proposed for fabricating these composites using the PIP method. The precursor solution, composed of zirconium tetrachloride, tetraethoxysilane, and furfuryl alcohol, exhibits lower viscosity, facilitating more efficient infiltration into the C/C matrix and reducing porosity in the final composite. Fine ZrC and SiC particles, with an average particle size of 2.03 μm, were homogeneously distributed within the composite matrix. The resulting material demonstrated a flexural strength of 193.2 MPa, along with linear and mass ablation rate of 0.03 μm/s and 0.10 mg/s, respectively. The uniform distribution of fine ZrC and SiC particles within the dense matrix significantly enhances mechanical properties and ablation resistance. During ablation, these particles promote the formation of a protective oxide scale consisting of a dense outer ZrO 2 layer and an inner SiO 2 layer. The dense ZrO 2 layer effectively retards oxygen diffusion into the composite, providing excellent resistance to mechanical erosion, while the continuous SiO 2 layer minimizes the ingress of oxidizing gases, further enhancing ablation resistance. This study demonstrates that the inorganic salt strategy can be used to fabricate C/C-ZrC-SiC composites at a lower cost while achieving superior properties, offering a promising approach for producing C/C-UHTCs composites.
研究领域:
材料科学
·
航空航天工程
✓ 已验证
产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2024
·
IF 20.2
Fu Li,Jingnan Yang,Xiaomei Zhou,Fei Han,Qian Huo,Qingxin Guan,Wei Li
Converting CO 2 to ethanol through photothermal catalysis faces significant challenges due to it involves multi-electron reduction and kinetically sluggish C-C coupling process. Here, copper and a minor quantity of palladium are encapsulated within the cage of UiO-66 using a dual-solvent-sonication method to form ultrafine Cu 2 O/Cu-Pd clusters. The Cu-Cu 2 O serves as an electron center to enhance CO 2 uptake and activation, while the incorporation of Pd accelerates H 2 activation. Due to differences in electronegativity , electrons tend to transfer from Cu to Pd, which reduces the electrostatic repulsion between intermediates and facilitates the coupling of *CO and *CHO. The photothermal ethanol yield of Cu 6 Pd@UiO-66 reached 1077.69 μmol·g cat –1 ·mL –1 with a selectivity of 94.62%, representing an 11.64-fold increase over the non-illumination, and a 3.11-fold enhancement compared with Cu 6 @UiO-66. This study offers evidence supporting the promotion of C-C coupling through an asymmetric electron distribution , potentially advancing the conversion of CO 2 to liquid products.
研究领域:
材料科学
·
催化化学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
Molecular Catalysis
·
2017
·
IF 0
Zhanao Lv,Haibin Wang,Zhuqi Chen,Shuhua Zou,Shuaishuai Zhu,Chenlin Lou,Guochuan Yin
Dioxygen activation as the solely terminal oxidant in organic synthesis and catalytic oxidation is particularly attractive from the point of economic and environmental view. In our previous study, we have displayed that the introducing of non-redox metal ions can sharply improve the olefin epoxidation catalyzed by ruthenium complex with PhI(OAc) 2 as the organic oxidation. Inspired by the successful strategy and dioxygen activation, in this study, we demonstrate an alternative protocol that adding non-redox metal ions to cis -Ru(bpy) 2 Cl 2 catalyst can remarkably improve the oxidation from Ru(II) to Ru(IV) = O with dioxygen as the oxidant and promote oxidative dehydrogenation of saturated C–C bond whereas Ru(bpy) 2 Cl 2 alone is very sluggish. Through UV–Vis, NMR, cyclic voltammogram and EPR characterization, it has been testified that oxidation from Ru(II) to Ru(IV) = O can be realized under the condition of 1 atm of dioxygen and 323 K within 25 min while extreme tough condition of 20 atm of dioxygen, 343 K and 8 h is necessary for Ru(bpy) 2 Cl 2 alone. Combined the reaction data with characterization results, an adduct of Ru(IV) = O/Sc(III) is proposed as the key active species to improve the catalytic efficiency. The activity improvement in oxidative dehydrogenation illustrated a novel strategy of that adding non-redox metal ions to sluggish catalysts can remarkably improve its efficiency for dehydrogenation of saturated C–C bond, especially through dioxygen as ultimate oxidant.
研究领域:
催化化学
·
有机合成
·
环境科学
✓ 已验证
产品关联
DOI
CERAMICS INTERNATIONAL
·
2022
·
IF 5.532
Ze Zhang,Cunqian Fang,Yuanqi Weng,Xiao Luo,Qizhong Huang,Huiping Hu
Graphene was introduced into C/C–SiC composites via pressureless impregnation to enhance the mechanical and thermal properties of the composites. The effects of various graphene contents on the mechanical and ablative performances of C/C–SiC composites were investigated. The results showed that the ultimate bending stress and compressive stress of the C/C–SiC composites increased by 28.98% and 23.64%, respectively, after adding 7.25% graphene. Moreover, the ablation rates of the composites were vastly decreased after adding a slight graphene content (2.13%). However, the ablation rates increased with increasing of graphene content, indicating that the benefit of introducing graphene on the ablation property decreased, which was mainly ascribed to the relative reduction in the SiC content. As a result, introducing slight graphene into C/C–SiC composites had the greatest benefit on the anti-ablation performance.
研究领域:
材料科学
·
航空航天工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）