Journal of Energy Chemistry
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2014
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IF 0
Pei Yu,Yong Shen Chua,Hujun Cao,Zhitao Xiong,Guotao Wu,Ping Chen
Alkali metal hydroxide and hydride composite systems contain both protic (H bonded with O) and hydridic hydrogen. The interaction of these two types of hydrides produces hydrogen . The enthalpy of dehydrogenation increased with the increase of atomic number of alkali metals, i.e., −23 kJ/mol H 2 for LiOH-LiH, 55.34 kJ/mol H 2 for NaOH-NaH and 222 kJ/mol H 2 for KOH-KH. These thermodynamic calculation results were consistent with our experimental results. H 2 was released from LiOH-LiH system during ball milling . The dehydrogenation temperature of NaOH-NaH system was about 150 °C; whereas KOH and KH did not interact with each other during the heating process. Instead, KH decomposed by itself. In these three systems, NaOH-NaH was the only reversible hydrogen storage system, the enthalpy of dehydrogenation was about 55.65 kJ/mol H 2 , and the corresponding entropy was ca. 101.23 J/(mol H 2 ·K), so the temperature for releasing 1.0 bar H 2 was as high as 518 °C, showing unfavorable thermodynamic properties. The activation energy for hydrogen desorption of NaOH-NaH was found to be 57.87 kJ/mol, showing good kinetic properties.
研究领域:
材料科学
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化学工程
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DOI
CRYSTENGCOMM
·
2022
·Vol. 24
·期 20
·3749-3761
·
IF 3.756
Mengya Li,Dandan Han,Junbo Gong
Uric acid (UA) is the end product of purine metabolism and is widely found in nature. Excess uric acid will result in the deposition of pathological uric acid crystals in the kidney. However, few studies have focused on the effects of components in the human body on the crystallization of uric acid. Herein, we found multiple effects of alkali metals (Na+, K+) on uric acid dihydrate (UAD) crystal growth, which is one of the main components of urinary stones. Optical microscopy (OM) and scanning electron microscopy (SEM) were employed to detect the crystal morphology, and long rod-like crystals and hierarchical crystals were found in the presence of Na+ and K+, respectively. Powder X-ray diffraction (PXRD) and micro-Raman spectroscopy verified that the crystal structure remained unchanged in the presence of ions. In addition, single-crystal growth experiments revealed that Na+ inhibited growth along [010] and [100], and K+ promoted growth along [100] but suppressed growth along [010]. The step growth of the UAD crystal was measured by atomic force microscopy (AFM), which indicated the inhibition of crystal growth by Na+ due to kink blocking, yet the promotion of crystal growth by K+ resulted from rough growth. Our studies showed that ions in the human body not only can maintain electrolyte balance but also can affect the crystallization of pathological crystals, which provides a suggestion for a rational diet for patients with hyperuricemia and urinary stones.
研究领域:
生物化学
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医学
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DOI
高影响因子
JOURNAL OF COLLOID AND INTERFACE SCIENCE
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2020
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IF 7.489
Runping Wu,Qing Ye,Kai Wu,Shuiyuan Cheng,Tianfang Kang,Hongxing Dai
The alkali metal (M = Na, K, Rb, and Cs)-modified C-FDU-15 (M-C-FDU-15( x ); x was the M/C-FDU-15 M ratio, and equal to 0.01–0.03) samples were prepared through an in situ process, and characterized by means of the TG, XRD, TEM, EDS, N 2 adsorption–desorption, O 2 -TPD, and CO 2 -TPD techniques. The (NO + O 2 ) adsorption mechanism was investigated using the (NO + O 2 )-TPD and DRIFTS techniques. The results show that the sequence of (NO + O 2 ) adsorption performance was Na-C-FDU-15(0.01) (104.1 mg/g) > K-C-FDU-15(0.01) (92.4 mg/g) > C-FDU-15 (76.2 mg/g) > Rb-C-FDU-15(0.01) (65.1 mg/g) > Cs-C-FDU-15(0.01) (62.3 mg/g). The alkali metal was uniformly distributed in C-FDU-15 and its doping enhanced the amount of the basic sites in the sample. Moreover, the optimal Na/C-FDU-15 M ratio was 0.02. (NO + O 2 ) were chemically adsorbed mainly in the forms of nitrite (NO 2 − ) and nitrate (NO 3 − ) on M-C-FDU-15( x ). A more amount of NO was converted to nitrate than to nitrite. There were three key factors of enhancing the (NO + O 2 ) adsorption capacity of C-FDU-15 due to alkali metal doping: the first factor was the increasing of surface area and pore volume of the sample, the second one was the enhancement in amount of the active sites in the sample, and the third one was the smaller alkali metal ionic radius in the sample.
研究领域:
材料科学
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环境科学
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DOI
PubMed
高影响因子
FUEL PROCESSING TECHNOLOGY
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2022
·
IF 8.129
Anbang Xu,Xin Huang,Guangchuan Tang,Lei Tang,Changlei Qin,Zhongqing Yang,Jingyu Ran
Levoglucosenone (LGO) has shown a promising potential in the application of the sustainable chemistry. In this work, alkali metal-doped phosphotungstic acids, M 2.5 H 0.5 PW 12 O 40 (M = Li, Na, K, Rb and Cs), were synthesized and employed for catalytic fast pyrolysis of cellulose to selectively produce LGO. The results show that levoglucosan , the main precursor of LGO, was produced with a yield of 33.5 wt% by non-catalytic pyrolysis of cellulose, while LGO by catalytic fast pyrolysis of cellulose is mainly regulated by the strong/weak acid sites of the M 2.5 H 0.5 PW 12 O 40 . Increasing the atomic radius of the alkali metals from Li to Cs doping to phosphotungstic acid led to an increase of LGO yield, attaining to 15.6 wt% at 300 °C over Cs 2.5 H 0.5 PW 12 O 40 due to a high strong/weak acid site ratio. In addition, LGO yield was further enhanced to 19.2 wt% over (NH 4 ) 2 HPO 4 modified Cs 2.5 H 0.5 PW 12 O 40 as a result of an increase of moderate strong acid sites. This study provides a potential method for LGO production by catalytic pyrolysis of cellulose.
研究领域:
化学工程
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可再生资源利用
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DOI
高影响因子
ADVANCED FUNCTIONAL MATERIALS
·
2023
·Vol. 33
·期 46
·2305436
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IF 19
Chenjie Han,Yeqing Lyu,Shaona Wang,Biao Liu,Yi Zhang,Jan J. Weigand,Hao Du,Jun Lu
Using ethanol electrocatalytic oxidation reaction (EOR) with a lower reaction potential to replace oxygen evolution reaction (OER) and integrating hydrogen evolution reaction (HER) have a promising development prospect for more energy-saving electrolytic hydrogen production. However, the main challenges of EOR are insufficient catalytic activity, high overpotential, and slow kinetics. Active sites on the electrocatalysts surface are occupied by alkali metal ion hydrate clusters by noncovalent interactions, which is considered to be one of the major causes of these challenges. To reduce the effect of the noncovalent interactions on the catalytic activity of the electrocatalyst, copper is chosen and doped in the form of a single atom in the electrocatalyst (Pt@Cu/C) to increase the electrocatalyst conductivity and make the anode contain more positive charge in this study. Then, alkali metal ion hydrate clusters are difficult to adsorb at the active site of Pt@Cu/C. The EOR electrocatalytic activity of Pt@Cu/C is up to 8184 mA mg Pt −1 , which is ≈4.8 times as high as that of Pt/C. The two-electrode hydrogen production device using Pt@Cu/C as anode for coupled EOR&HER requires a smaller voltage of 0.60 V to reach 10 mA cm −2 compared with that of Pt/C (0.76 V).
研究领域:
电化学
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催化
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能源材料
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氢气生产
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产品关联
DOI
高影响因子
Frontiers in Chemistry
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2022
·
IF 5.545
Zhao Jinchong,Jiang Jie,Wen Song,Zhang Jing,Zhang Changsheng,Sheng Nan,Liang Wei,Sun Bing,Xu Wei,Yang Zhe,Pan Yuan
A series of alkali metal (Li, Na, and K)-modified Pd catalysts and Pd/Al2O3 were prepared and used to remove oxygen in a propylene flow with hydrogen’s existence. The results showed that the alkali metals could enhance the performance of the Pd catalysts and the effect followed the order of K > Na > Li. X-Ray diffraction (XRD), N2-physisorption, transmission electron microscopy (TEM), hydrogen temperature programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS) were carried out to investigate the alkali metal-modified Pd catalysts and the promotional effect mechanism was explained. The results showed that alkali metal modification increased the electron density of Pd atoms to induce the negatively charged Pd species, which could enhance the adsorption of oxygen while weakening the adsorption of propylene, and then enhance the performance of the modified catalysts for oxygen removal from unsaturated hydrocarbon. The Pd-K/A catalyst performed the best on both oxygen removal and propylene hydrogenation inhibition.
研究领域:
催化化学
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材料科学
✓ 已验证
DOI
PubMed
高影响因子
JOURNAL OF PHYSICAL CHEMISTRY B
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2023
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IF 3.3
Zhuanfang Jing,Yongquan Zhou,Toshio Yamaguchi,Koji Ohara,Jianming Pan,Guangguo Wang,Fayan Zhu,Hongyan Liu
The underlying recognition mechanisms of alkali metal ions by crown ethers in aqueous solutions are yet to be fully understood at the molecular level. We report direct experimental and theoretical evidence for the structure and recognition sequence of alkali metal ions (Li+, Na+, K+, Rb+, and Cs+) by 18-crown-6 in aqueous solutions by wide-angle X-ray scattering combined with an empirical potential structure refinement modeling and ab initio molecular dynamics simulation. Li+, Na+, and K+ are located in the negative potential cavity of 18-crown-6, with Li+ and Na+ deviating from the centroid of 18-crown-6 by 0.95 and 0.35 Å, respectively. Rb+ and Cs+ lie outside the 18-crown-6 ring and deviate from the centroid of 18-crown-6 by 0.05 and 1.35 Å, respectively. The formation of the 18-crown-6/alkali metal ion complexes is dominated by electrostatic attraction between the cations and the oxygen atoms (Oc) of 18-crown-6. Li+, Na+, K+, and Rb+ form the H2O···18-crown-6/cation···H2O “sandwich” hydrates, while water molecules only hydrate with Cs+ of the 18-crown-6/Cs+ complex on the same side of Cs+. Based on the local structure, the recognition sequence of 18-crown-6 for alkali metal ions in an aqueous solution follows K+ > Rb+ >Na+ >Li+, which is completely different from that (Li+ > Na+ > K+ > Rb+ > Cs+) in the gas phase, confirming that the solvation medium seriously affects the cation recognition of crown ethers. This work provides atomic insights into understanding the host–guest recognition and solvation behavior of crown ether/cation complexes.
研究领域:
化学
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物理化学
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DOI
PubMed
高影响因子
Catalysts
·
2023
·Vol. 13
·期 3
·552
·
IF 3.9
Bingxin Guo,Chengfei Zhao,Yingshuang Zhou,Junjie Guo,Zhongzhe Wei,Jing Wang
Alkali metals, as ideal electron donors, can effectively regulate the valence state distribution of the host metals. Nevertheless, no studies have reported the application of alkali metal promoters in the hydrogen evolution reaction (HER). Here, we designed an efficient and wide pH-universal hydrogen evolution catalyst that utilizes alkali metal to control the valence, size, and dispersion of Ru NPs. The experimental results reveal that the alkali metal additives contribute to the dispersion and stabilization of metallic Ru. More importantly, the interaction between Na and Ru regulates the distribution of Ru valence states and helps to form more active components of Ru0. Additionally, NaCl functioned as an in situ template to assist the construction of a porous carbon skeleton promotes mass transfer and exposes more active sites, further promoting the synergistic effect of Ru and Na. As a result, the optimal Ru0.3/C−800 delivers high efficiency for HER with an overpotential as low as 29 mV in 1.0 M KOH and 83 mV in 0.5 M H2SO4under 10 mA cm−2. Particularly, the catalytic performance of Ru0.3/C−800 even outbalanced that of commercial Pt/C in an alkaline medium. This rational construction strategy opens up new avenues for obtaining superior pH-universal electrocatalysts.Keywords:alkali metal;Ru based;hydrogen evolution reaction;wide-range pH;promotional effect
研究领域:
化学
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材料科学
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DOI
高影响因子
ENERGY & FUELS
·
2024
·
IF 5.2
Hongming Liu,Junhui Liang,Jiaxin Li,Yuhui Du,Hangning Chen,Chenhao Du,Liuqi Wang,Yincheng Li,Yuexiang Huang,Da Chen
While ammonia serves as a carbon-free hydrogen carrier, addressing challenges in hydrogen energy storage and transportation, the present technology for thermocatalytic ammonia decomposition encounters constraints owing to elevated decomposition temperatures. Alkali metal promoters have been demonstrated to effectively lower the reaction temperature. However, their precise role in the process of ammonia dehydrogenation remains not fully understood. Herein, we investigated the impact of alkali metals by incorporating various base treatments (with (i.e., KOH) or without alkali metals (i.e., NH3·H2O)) during the deposition process. The results indicate that compared to samples without alkali metal treatment, catalysts with added alkali metals (5 wt % Ru/CeO2-NP(KOH)) show a 16.7% improvement in ammonia decomposition efficiency and a 5.54 mmol gcat–1 min–1 increase in hydrogen production rate under the same test conditions (500 °C, gas hourly space velocity (GHSV) of 30,000 mL gcat–1 h–1). This phenomenon may be attributed to the dual promotion of alkali metal K in regulating both vacancy defects and metal active sites. The regulatory mechanism of alkali metal activity proposed by us not only provides a better understanding of the specific role of alkali metals in the reaction process but also holds significant implications for guiding the design of novel catalysts.
研究领域:
催化化学
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能源材料科学
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产品关联
DOI
高影响因子
JOURNAL OF LUMINESCENCE
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2020
·
IF 3.28
Hui Yu,Xinan Shi,Lijian Huang,Xiaojiao Kang,Daocheng Pan
Eu 3+ /Tb 3+ -doped CaMoO 4 /SrMoO 4 luminescent thin films were deposited by a facile solution method, and were annealed over the temperature range of 350–650 °C. Luminescent thin films were characterized by means of X-ray diffraction (XRD), photoluminescence (PL), UV–vis absorption, scanning electron microscope (SEM) and energy disperse spectroscopy (EDS). In addition, the effects of alkali metal ions (Li + , Na + and K + ) on the luminescence properties of CaMoO 4 /SrMoO 4 thin films were systematically investigated. We found that the optimal chemical compositions for the luminescent molybdate thin films are Ca 0.87 MoO 4 :Eu3+ 0.10, K+ 0.03, Sr 0.82 MoO 4 :Eu3+ 0.15, K+ 0.03, Ca 0.87 MoO 4 :Tb3+ 0.03, Li+ 0.1, and Sr 0.82 MoO 4 :Tb3+ 0.15, Li+ 0.03.
研究领域:
材料科学
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光学
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DOI
高影响因子
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE
·
2020
·Vol. 646
·期 20
·1688-1695
·
IF 1.24
Shuangsheng Cheng,YuanDong Wu,Dajiang Mei,Shaoguo Wen,Thomas Doert
Four alkali metal bismuth sulfates, NaBi(SO 4 ) 2 · H 2 O ( 1 ) and ABi(SO 4 ) 2 [A = K ( 2 ), Rb ( 3 ), Cs ( 4 )], were successfully synthesized by hydrothermal methods. The crystal structure of 1 features a three-dimensional tunnel framework constructed by BiO 9 tri-capped trigonal prisms and SO 4 tetrahedra interconnected via common corners and edges. Compound 2 exhibits a two-dimensional 2 ∞ [Bi(SO 4 ) 2 ] – double-layered structure, assembled by one-dimensional 1 ∞ [BiS(1)O 4 ] + chains which are linked via S(2)O 4 2– tetrahedra. The isostructural compounds 3 and 4 possess a two-dimensional layered structure, and the layers being composed by BiO 8 square antiprism and SO 4 tetrahedra. The alkali metal cations are located between the layers or in the tunnels of the structures, respectively. The differences in the crystal structures of the title compounds can mainly be attributed to the different sizes of the alkali metal cations and their different coordination environments. Thermogravimetric analysis evidence that compound 1 losses one equivalent of water at 120 °C whereas the anhydrous compounds 2 – 4 are stable up to about 450, 575, and 578 °C, respectively. The solid-state UV/Vis/NIR diffuse reflectance spectra indicate bandgaps of approximately 4.48, 4.43, 3.98, and 3.96 eV for compounds 1 – 4 , respectively.
研究领域:
化学
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材料科学
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DOI
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2016
·
IF 3.349
He Han,Min Liu,Xiaowa Nie,Fanshu Ding,Yiren Wang,Junjie Li,Xinwen Guo,Chunshan Song
The side-chain alkylation of toluene with methanol was investigated on a series of catalysts which were prepared by ion-exchange or subsequent impregnation of zeolie X with potassium hydroxide or cesium hydroxide aqueous solution. The catalysts were characterized by X-ray diffraction, scanning electron microscopy, X-ray fluorescence, Ar physical adsorption-desorption, NH 3 temperature-programmed desorption (TPD), CO 2 -TPD, pyridine adsorption Fourier-transform infrared (FT-IR) spectroscopy, FT-IR spectroscopy in O H stretch region, thermogravimetric/differential thermal analysis, ultraviolet-Raman spectroscopy, and X-ray photoelectron spectroscopy. It was found that alkali metal oxide played extremely important roles in the modification of catalysts and in the catalytic reaction pathway. Strong basic sites were formed by modification of basic zeolite X with alkali metal oxide. These basic sites promoted the dehydrogenation of methanol to formaldehyde which was recognized as the true alkylating agent in side-chain alkylation. Consequently, side-chain alkylation of toluene with formaldehyde was enhanced. As toluene was mainly adsorbed and activated on alkali metal cations bonded on the zeolite framework, the synergistic effects between alkali metal oxide and alkali metal cations were proposed. One of the possible reaction path ways for side-chain alkylation of toluene with methanol over basic zeolite was described. Alkali metal ion-exchanged zeolite X modified with alkali metal oxide demonstrated relatively high side-chain alkylation activity. However, the improvement of styrene selectivity faced with great challenges.
研究领域:
化学工程
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催化科学
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产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）