INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
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2023
·
IF 7.2
Lei Dai,Peng Fu,Jieming Chen,Fazhe Sun
The band gap width has always been the main reason for the low photocatalytic performance of TiO 2 semiconductors. “Band gap engineering” is often used to change the band gap width of TiO 2 . On this basis, the impurity band gap was induced below the TiO 2 conduction band by regulating N element. What's interesting was that N element adjusted the valence state of adjacent Ti element and caused the generation of oxygen vacancy . This is due to the extraction of neutral oxygen atoms, resulting in electron transfer to the Ti cation band structure . The 300-N-T catalyst exhibited the best photocatalytic hydrogen production performance under visible light, which was 307.65 μmol/(g·h) and was 61.53 times higher than that of anatase. And the concentration of Ti 3+ defects and oxygen vacancy reduced with decreasing of N content in TiO 2 . According to Kubelke Munk formula, the band gap of 300-N-T photocatalyst was narrowed to 2.73 eV, which indicated that there are impurity energy levels near the CB and VB of TiO 2 material. The Ti 3+ ions as the active site of the photocatalytic reaction was confirmed by instantaneous photocurrent response and EIS characteristic. This study revealed the structure-activity relationship between the content of N element, Ti 3+ ions and oxygen vacancy in TiO 2 materials, as well as the decisive process of defect induced visible light catalysis.
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Molecular Catalysis
·
2023
·
IF 4.6
Tingting Ma,Chao Xu,Fengyang Liu,Yirong Feng,Wenyan Zhang,Weiwei Tang,Haoyu Zhang,Xiaowei Li,Yingying Nie,Shuangfei Zhao,Yuguang Li,Dong Ji,Zheng Fang,Wei He,Kai Guo
Selective epoxidation and allylic oxidation of cyclohexene were realized in the presence of BEA-Ti and (metallo)porphyrin catalysts. The integration of BEA-Ti and porphyrin H 2 MTPP afforded cyclohexene oxide with excellent selectivity (cyclohexene oxide/ 2-cyclohexen-1-one=85:15). BEA-Ti and metalloporphyrin MnMTPP yielded 2-cyclohexen-1-one with high selectivity (cyclohexene oxide/ 2-cyclohexen-1-one=12:88). Resulting active species involving of (metallo)porphyrin, Ti IV sites and tert-butyl hydroperoxide (TBHP) promoted the oxidation process of cyclohexene. A possible mechanism resulting in the formation cyclohexene oxide and 2-cyclohexen-1-one was proposed. The outer-sphere effect constructed by (metallo)porphyrin, Ti IV sites and TBHP on the surface of BEA-Ti framework improved the epoxidation and allylic oxidation both in the conversion and selectivity.
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Journal of the Australian Ceramic Society
·
2023
·Vol. 59
·期 5
·1231-1239
·
IF 1.9
Zhang Mengwen,Jiang Binyang,Yang Lutong,Cao Na,Li Zhaosheng,Fan Lei,Yang Shoulei
The emerging oscillatory pressure sintering technology is used to prepare high-performance Al 2 O 3 -Ti(C,N) ceramic tools for high-speed cutting. By recording the displacement during sintering, the sintering shrinkage rate of the Al 2 O 3 -Ti(C,N) composite was calculated, and the stress exponent n and sintering activation energy Q were calculated according to creep theory to determine the densification mechanism. In addition, the evolution of phases, microstructure and hardness of the composite was also observed. Results show that during oscillatory pressure sintering process at 1400 °C and 1300 °C, the stress exponent of Al 2 O 3 -Ti(C,N) composite is around 2.2 and the sintering activation energy is 486 kJ mol −1 , indicating that the densification mechanism is a diffusion-controlled grain boundary sliding of Al 2 O 3 phase. Additionally, as the oscillatory pressure increases, the average grain size of the Al 2 O 3 decreases and the Vickers hardness increases. Hardness achieves the highest 22.7 GPa when the median oscillatory pressure is 70 MPa at 1400 °C, which is 1 GPa higher than that of static pressure of 70 MPa.
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CHEMICAL ENGINEERING JOURNAL
·
2023
·
IF 15.1
Shanshan Zhang,Guizhen Liu,Sihai Lv,YingLi Zhu,Pingan Chen,Hui Luo,Xiangcheng Li,Fu Chen
Magnetic carbon-based microwave absorption materials (MAMs) derived from metal-organic frameworks (MOFs) have been regarded as promising candidates for addressing the electromagnetic pollution. The construction of magnetic carbon-based MAMs derived from MOFs with ferromagnetic centers (Fe, Co, Ni etc.) and their composites has become a mainstream in recent years. However, MOFs with non-magnetic centers have received less attentions due to the challenges in achieving magnetic-dielectric synergistic effect and proper impedance matching in their derivatives. In this work, a facile metal-polyphenol network coating strategy has been proposed to facilitate the construction of magnetic MWCNTs decorated TiN 0.9 /NC absorber derived from non-magnetic MIL-125(Ti). The regulation effect of carbothermal temperature on magnetism, defect density, graphitization degree as well as electromagnetic parameters of absorbers have been systematically investigated. The obtained composites exhibit outstanding microwave absorption performance due to the magnetic-dielectric synergistic effect and improved impedance matching. The minimum reflection loss reaches −42.55 dB at 1.91 mm and the effective absorption bandwidth reaches as wide as 4.6 GHz with an ultra-thin thickness of only 1.38 mm. It is believed that this study provides a new way to construct efficient magnetic carbon-based MAMs with non-magnetic metal-based MOFs and a meaningful exploration for the preparation of ultra-thin absorbers.
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JOURNAL OF COORDINATION CHEMISTRY
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2023
·
IF 1.9
Jinyan Tan,Na Zhang,Ling Wang,Liduo Chen,Cuiqin Li,Jun Wang
Metal-organic framework MIL-125(Ti)-NH2 was prepared and coordinated with salicylaldehyde and NiCl2·6H2O to create a heterogeneous catalyst for ethylene polymerization. The structure of the products was characterized by a variety of physical methods, such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma mass spectrometry (ICP-MS), and nitrogen adsorption-desorption. The catalytic performance of MIL-125(Ti)-NH2-Sal-Ni was also investigated. The results showed that the reaction temperature, Al/Ni molar ratio, and ethylene pressure influenced on the catalytic activity and product selectivity. Under optimal reaction conditions, the catalytic activity of MIL-125(Ti)-NH2-Sal-Ni for ethylene oligomerization could reach 5.90 × 104 g·(mol Ni·h)−1 using cyclohexane as the solvent and MAO as the co-catalyst; the main products were C4 and C6. In addition, MIL-125(Ti)-NH2-Sal-Ni had good catalytic stability and recycling, which could be reused at least twice without significant loss of activity. Moreover, based on the evaluation of catalytic performance, the catalytic ethylene oligomerization mechanism of MIL-125(Ti)-NH2-Sal-Ni was also deduced.
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International Journal of Applied Ceramic Technology
·
2023
·
IF 2.1
Mengwen Zhang,Na Cao,Fanyu Meng,Lutong Yang,Binyang Jiang,Jinsheng Li,Lei Fan,Shoulei Yang
High-toughness Al 2 O 3 –Ti(C,N) composites reinforced by cBN particles were prepared by the new oscillating pressure sintering technique. The density, phase, and microstructure evolution of the Al 2 O 3 –Ti(C,N)-cBN composites sintered at different temperatures were studied, and their effects on the mechanical properties were investigated. The results show that when the sintering temperature increases from 1300 to 1500°C, the heat preservation time shortens, whereas the density and interface bonding strength of the composites increase. In addition, cBN particles can play the role of crack bridging and be pulled out when the composites fracture, improving the toughness of the Al 2 O 3 –Ti(C,N)–cBN composites. However, when the sintering temperature further rises to 1600°C, a new phase of TiB 2 forms, and the solid solubility of C and N in Ti(C,N) increases, leading to a decrease in density and mechanical properties. As a result, when the Al 2 O 3 –Ti(C,N)–cBN composite is sintered at 1500°C, its mechanical properties reach the maximum values of 21.5 GPa, 5.7 MPa m 1/2 , and 731 MPa for hardness, fracture toughness, and flexural strength, respectively.
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Catalysis Science & Technology
·
2022
·Vol. 12
·期 15
·4837-4850
·
IF 6.177
Haoyi Lin,Jiaxing Zhang,Qingxu Duan,Kaixuan Yang,Weiping Liao,Shixue Qi,Hongying Lü,Zhiguo Zhu
Plentiful heteroatom-containing zeolites as versatile redox catalysts have been successfully post-synthesized via the top-down methodology, where the starting aluminosilicate zeolites are normally expected to be highly dealuminated to maximize the amounts of silanol nests and occasionally to evade the detrimental effect of framework Al ions on the catalytic performance. Herein, our proposed dealumination-controlled strategy for the synthesis of hierarchical Ti–Y zeolite breaks through this concept. Framework-substituted Ti and tri-coordinated Al species were afforded from the interaction of Ti ions with dealumination-derived silanol nests and from the process of acid treatment, respectively. Structure–function relationships revealed that Lewis acid sites were the catalytically active centres of Ti–Y zeolite in oxidative desulfurization with hydrogen peroxide as the oxidant, which came from the cooperative effect of dual active sites containing framework-substituted Ti and tri-coordinated Al species. The amounts of Lewis acid sites demonstrated a volcanic-type trend as the acid-treatment time increases. The reusability, regeneration ability, deactivation mechanism were also systematically investigated in oxidative desulfurization. Thus the Ti–Y zeolite catalyst was also effective for Baeyer–Villiger oxidation of 2-adamantanone. This work discloses the effectiveness of preparing an efficient Ti–Y zeolite catalyst with cooperative dual active sites via a dealumination-controlled strategy, which bears potential application for constructing other heteroatom-containing FAU-type zeolites with Lewis acid property.
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APPLIED SURFACE SCIENCE
·
2022
·
IF 7.392
Menghan Qin,Yumiao Shi,Dingkun Lu,Jingjing Deng,Guoyue Shi,Tianshu Zhou
Due to the excessive use, cephalosporin antibiotics have been detected in various aquatic environments, which may result in environmental and health concern. In this study, bimetallic metal–organic frameworks (MOFs), Hf-UiO-66 and Ti-UiO-66, were successfully designed and obtained via post-synthetic method from UiO-66 for the adsorption of cefoperazone. A serious of adsorption experiments were investigated. The adsorption kinetics and isotherms demonstrated that the adsorption process followed pseudo-second-order kinetic model and Langmuir isotherm model. Hf/Ti-UiO-66 exhibited much better adsorption performance than the undoped UiO-66. Particularly, Hf-UiO-66 had the highest adsorption capacity (346.0 mg g −1 ). With the introduction of Hf or Ti, the chemical coordination environment changed, which resulted in defective structures of MOFs. Such defective structures increased the adsorption active sites, changed the surface charges and enlarged pores. Based on the characterization by FT-IR, XPS, and zeta potential, it was identified that the electrostatic attraction, π-π stacking, hydrogen bonding and metal complexation were the driving force for the high adsorption capacity of the bimetallic MOFs. The as-prepared MOFs displayed good stability and reusability. This work provides a great prospect for the design and application of bimetallic defective MOFs in cephalosporins removal in environmental water.
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KOREAN JOURNAL OF CHEMICAL ENGINEERING
·
2022
·Vol. 39
·期 1
·96-108
·
IF 3.146
Zeng Xingye,Adesina Adeyemo,Li Ping,Wang Hanlu,Zhou Rujin
Ti-containing Mobil composition of matter-twenty-two (Ti-MWW) zeolite was prepared via a two-step post-synthesis process and then characterized by X-ray fluorescence, nitrogen adsorption-desorption isotherms, Fourier transform infrared absorption spectra, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectra. These results indicate that the textural properties of MWW were well preserved after acid treatment and incorporation of titanium. An adsorptive-oxidative desulfurization (AODS) system was successfully developed on the basis of a model oil containing dibenzothiophene (DBT) with the as-prepared Ti-MWW being the catalyst and adsorbent and cumene hydroperoxide (CHP) being the oxidant. The parameters influencing the desulfurization performance were systematically investigated. These parameters include the Ti-MWW dosage, the reaction temperature, the stirring speed, the molar ratio of CHP to DBT and the additions of olefins and aromatics to the system. The conversion rate of DBT reached 99.6% via the catalytic oxidation process and the turnover frequency was 40.1 h −1 . Meanwhile, the oxidation products of DBT were removed by Ti-MWW adsorption. The recycling and regeneration performance of Ti-MWW were also investigated, and the DBT conversion reached 99.5% using the regenerated Ti-MWW. This work provides useful information for the construction of solvent-free oxidative desulfurization systems using a zeolite.
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Journal of Materials Research and Technology-JMR&T
·
2023
·
IF 6.4
Jiayin Chen,Zeyun Cai,Weizong Bao,Tian Gao,Guoqiang Xie
The trade-off between strength and ductility is a prevalent issue in strengthening commercially pure titanium (CP–Ti). This study presents a method to prepare ultra-high strength Ti–N alloys with adequate ductility using ball-milling (BM) and spark plasma sintering (SPS) techniques, based on nitrogen solid solution and grain refinement strengthening. The effect of ball milling time of mixed powders on mechanical properties of Ti–N alloys was studied systematically. Quantitative analysis reveals that solid solution strengthening and grain refinement strengthening worked synergistically to enhance yield strength of alloys. The Ti–N alloys with the most favorable mechanical properties demonstrated a yield strength of 1606 MPa and a compressive plastic strain of 14.44 %. The development of novel Ti–N alloys provides a viable strategy for the advancement of high-performance titanium alloys using ubiquitous elements.
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CHEMICAL ENGINEERING JOURNAL
·
2021
·
IF 13.273
Yueyue He,Wei Xiang,Genpin Lv,YanJun Zhong,Yang Song,Kun Zhou,Zhenguo Wu,Jun Zhang,Erqiang Yang,Xiaodong Guo
The recent discovery of fast Li-ion transport networks in Li-rich disordered rock-salt (DRX) cathodes expands vastly composition space of high-energy–density cathode materials. Despite numerous Nb, Mo and W based DRX materials have been reported, high energy density DRX materials with composition of inexpensive, eco-friendly and earth abundant elements still urgently need to be developed. Herein, a promising set of Ti based oxyfluorides Li 2 Ti 1/3 Ni 1/3 M 1/3 O 2 F (M = Mn, Fe), which contain high voltage Ni 2+ /Ni 4+ redox couple and low-cost redox couple with Fe and Mn were successfully synthesized. Benefited from the stable Ni 2+ / 4+ and Mn 3+ / 4+ redox and moderated anion redox, Li 2 Ti 1/3 Ni 1/3 Mn 1/3 O 2 F oxyfluoride exhibits high discharge capacities of 285.3 mAh g −1 and energy content of 909.5 Wh kg −1 as well as relatively stable cyclability. Especially, high discharge capacity of 215 mAh g −1 above 3 V acquired by coordination utilization of cation and anion redox for Li 2 Ti 1/3 Ni 1/3 Mn 1/3 O 2 F endows the oxyfluoride with high energy quality, showing enormous potential for practical utilization in the future. For Li 2 Ti 1/3 Ni 1/3 Fe 1/3 O 2 F, the poor reversibility of Ni 2+ /Ni 4+ redox and much higher oxygen charge redox are the main reasons for the much worse capacity retention, and the activation of Fe 2+ /Fe 3+ redox at low voltage partially contributes to the decreased discharge voltage. Density-functional theory calculation reveals that localized oxygen 2p orbital of Li 2 Ti 1/3 Ni 1/3 Fe 1/3 O 2 F is closer to the Fermi level than that of Li 2 Ti 1/3 Ni 1/3 Mn 1/3 O 2 F, which would ultimately lead to much higher content of oxygen redox and relatively lower capacity retention. The synergistic utilization of multiple cation redox reservoirs which consist of high voltage redox couple and low-cost redox couple, and small quantity of O redox centers to construct high energy quality DRX materials would provide new reference for developing other cathodes.
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Catalysts
·
2021
·Vol. 11
·期 1
·82
·
IF 4.146
Chuang Li,Dan Wang,Jiangli Gu,Yichun Liu,Xintong Zhang
Surface electron traps on semiconductor photoanodes mediate surface recombination and deteriorate the photoelectrochemical (PEC) water oxidation performance of the photoanode. Developing convenient methods to reduce surface electron traps is therefore essential for high efficiency PEC water oxidation on semiconductor photoanodes, particularly for nanostructured photoanodes with large surface area. Herein, we employ a O2plasma treatment to boost the PEC water oxidation performance of Ti-doped Fe2O3(Ti-Fe2O3) nanowires photoanodes, aiming to reduce surface oxygen vacancies, the dominant electron traps on Ti-Fe2O3surface. X-ray diffraction (XRD), scanning electron microscopy and spectroscopic analyses show that the oxygen plasma treatment changes the structural, morphological and optical properties negligibly, but it does reduce the content of surface oxygen vacancies, as estimated from O1s X-ray photoelectron spectroscopy spectra. An optimal O2plasma treatment (200 W, 70 s) increases the photocurrent density of the Ti-Fe2O3nanowire photoanode to 2.14 mA·cm−2(1.23 V vs. RHE) under air mass 1.5G simulated solar light, which is 1.95 times higher than the pristine Ti-Fe2O3nanowire photoanode. The surface hole transfer efficiency is also improved by 1.66 times due to the reduced surface recombination. The work suggests that O2plasma treatment is a convenient but effective method to boost the PEC water oxidation performance of Ti-Fe2O3photoanode and might be applicable to other semiconducting oxide photoanodes for high efficiency PEC water splitting.Keywords:photoelectrochemical water splitting;O2plasma treatment;surface oxygen vacancies;Ti-doped hematite nanowire arrays
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