Catalysis Science & Technology
·
2017
·Vol. 7
·期 20
·4640-4647
·
IF 5.773
Fangfang Wu,Xiaoqin Sun,Gang Liu,Xiaoxiang Xu
Despite a strong visible light absorption at a wavelength as far as 610 nm, SrTaO2N generally exhibits poor photocatalytic activity due to photocatalytic self-decomposition. In this study, we introduce Na into the B site of SrTaO2N and perform an investigation on its crystal structure, optical absorption and photocatalytic water oxidation in response to Na incorporation. Our results suggest that Na incorporation effectively enhances local Ta–O(N) bond strength, which is responsible for strong interband light absorption, low tendency to defect formation and high stability against photocatalytic self-decomposition. Efficient photocatalytic water oxidation was realized in Na-modified SrTaO2N (Sr0.8Na0.2TaO2.8N0.2) with an apparent quantum efficiency as high as 0.2% under visible light illumination (≥400 nm). This simple strategy highlights the benefits of alkaline metal modification and can be extended to other nitrides or oxynitrides where management of local bond strength is needed.
研究领域:
材料科学
·
光化学
·
能源转化
·
表面化学
·
无机化学
✓ 已验证
DOI
高影响因子
JOURNAL OF ELECTRONIC MATERIALS
·
2018
·Vol. 47
·期 12
·7514-7519
·
IF 1.566
Zhu Z.,Zhang Y. W.,Song H. Z.,Li X. J.
Cu 1.98− x Na x Se nanopowders were synthesized using a hydrothermal method and hot-pressed into bulk pellets to assess the effects of Na doping on the thermoelectric properties of Cu 1.98 Se. The original layered microstructure was maintained at low doping levels, although nanopores, together with point defects, appeared to decrease the thermal conductivity. The thermoelectric properties of the material were improved by Na doping, resulting in a maximum ZT value of 1.32 for Cu 1.94 Na 0.04 Se at 973 K. The experimental data indicate that an optimal level of Na doping effectively improves the thermoelectric performance of non-stoichiometric Cu 1.98 Se.
研究领域:
材料科学
·
热电学
✓ 已验证
产品关联
DOI
高影响因子
Materials Today Communications
·
2022
·
IF 3.662
Yanfei Jia,Jianwen Wei,Yuan Yuan,Xiaobin zhou,Linlin Geng,Lei Liao
Using KIT-6 as the silica source, a series of Li 4 SiO 4 adsorbents (KIT-6-Li 4 SiO 4 ) were synthesized by impregnation precipitation method for high temperature CO 2 capture. Then, the KIT-6-Li 4 SiO 4 -800–4 (KL-800–4) material, was selected to analyze the improvement of the adsorption performance by Ca 2+ /Na + eutectic doping modification. These adsorbents were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and low temperature N 2 adsorption/desorption, and the CO 2 adsorption capacity of them was explored. At 600 °C and under 15 vol% CO 2 , KL-Ca0.03 and KL-Na0.06 sorbents resulted in a CO 2 uptake of 29.17 wt% and 35.35 wt% (close to the theoretical maximum), respectively，which are much higher than that of KL-800–4 (14.73 wt%). After 10 adsorption/desorption cycles, the adsorption capacity of KL-Na0.06 increased by 1.35 wt%. We found that KL-Na0.06 has more advantages compared with traditional lithium orthosilicate and undoped adsorbents, including lower energy consumption, higher CO 2 adsorption capacity and better cycling ability. Finally, the double exponential model had a high degree of fit for the adsorption of CO 2 by Li 4 SiO 4 .
研究领域:
材料科学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2014
·
IF 2.726
L.W. Wang,F. Wu,D.X. Tian,W.J. Li,L. Fang,C.Y. Kong,M. Zhou
In this paper, Na-doped ZnO (NZO) thin films with doping contents of 3–30 at.% were synthesized on quartz glass substrates by sol–gel spin coating method. The structure, morphology, optical transmittance and photoluminescence properties of NZO films were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), atomic force microscope (AFM), UV–VIS spectrometer and fluorescence spectrophotometer, respectively. The results showed that all the NZO thin films exhibit a strong preferential c -axis orientation with a hexagonal polycrystalline structure. An apparent increase in crystallinity was observed with the increasing Na content. The surface of the heavily Na doped samples (30 at.%) exhibits nanorods morphology. The RMS roughness changed from 16.219 nm to 53.072 nm with the increase of Na concentrations. As Na doping content increases to 24 at.%, the average transmittance was still larger than 62% in the visible range. The optical band gap initially increased and then decreased nearly linearly with the increase of Na content. The refractive index of NZO films in the visible range was found to increase gradually with increasing Na dopants. Room temperature photoluminescence (PL) spectra showed sharp ultraviolet emissions centered at 388 nm and broad green–yellow emissions (450–650 nm). The violet emission centered at 424 nm appeared in the spectra of 30 at.% NZO. In addition, it was found that the low Na doping concentration contributed to the enhancement of I NBE / I DLE .
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Materials & Interfaces
·
2022
·
IF 10.383
Adeel Abbas,Mohammad Nisar,Zhuang Hao Zheng,Fu Li,Bushra Jabar,Guangxing Liang,Ping Fan,Yue-Xing Chen
Recently, rock-salt lead-free chalcogenide SnTe-based thermoelectric (TE) materials have been considered an alternative to PbTe because of the nontoxic properties of Sn as compared to Pb. However, high carrier concentration that originated from intrinsic Sn vacancies and relatively high thermal conductivity of pristine SnTe lead to poor TE efficiency, which makes room for improving its TE properties. In this study, we present that the Na incorporation into the SnTe matrix is helpful for modifying the electronic band structure, optimization of carrier concentration, introducing dislocations, and kink planes; benefiting from these synergistic effects obviates the disadvantages of SnTe and makes a significant improvement in TE performance. We reveal that Na favorably impacts the structure of electronic bands by valence, conduction band engineering, leading to a nice enhancement in the Seebeck coefficient, which exhibits the highest power factor value of 37.93 μWcm–1 K–2 at 898 K, representing the best result for the SnTe material system. Moreover, a broader phonon spectrum is introduced by new phonon-scattering centers, scattered by dislocations and kink planes which suppressed lattice thermal conductivity to 0.57 Wm–1 K–1 at 898 K, which is much lower than that of pristine SnTe. Ultimately, a maximum ZT of 1.26 at 898 K is achieved in the Sn1.03Te + 3% Na sample, which is 97% higher than that of the pristine SnTe, suggesting that SnTe-based materials are a robust candidate for TE applications specifically, an ideal alternative of lead chalcogenides for TE power generation at high temperatures.
研究领域:
材料科学
·
能源工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CATALYSIS COMMUNICATIONS
·
2019
·
IF 3.674
Feng Wang,GuoQin Qi,ChuanQi Zhang,HeCheng Ren,Hua Ma,Yu Guo
A series of Na-doped Pt/Al 2 O 3 catalysts with 0.2 wt% of Pt loading and 0–6 wt% Na loading was prepared to investigate the HCHO complete oxidation at room temperature. Powder XRD, BET and XPS were used to characterize the bulk structure and texture of catalysts, as well as the ratio of hydroxyl oxygen to lattice oxygen. A long-term catalyst stability test (50 h on reaction stream) was conducted under severe conditions of a large space velocity of 180,000 mL/h/g, a high HCHO concentration of 80 ppm and dry conditions (relative humidity of 0%). An appropriate amount of doped-Na (2 wt%) contributed to a remarkable improvement of activity and stability of the Na-doped 0.2 wt% Pt/Al 2 O 3 catalyst.
研究领域:
催化化学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Energy Materials
·
2024
·
IF 5.4
Jiahao Xu,Kangwei Hou,Xiaolin Li,Yuhan Bian,Yaping Wang,Li Wang,Guangchuan Liang
The practical applications of lithium manganese iron phosphate (LMFP) are severely circumvented by the inferior electronic conductivity and electrochemical reaction kinetics. In this work, a Na+-doping method is adopted to prepare Li1–xNaxMn0.6Fe0.4PO4/C (x = 0, 0.01, 0.02, 0.03) materials by spray drying combined with the carbothermal reduction method. It is found that appropriate Na+ doping enhances the crystallinity, reduces Li–Fe antisite defects, decreases the primary particle size, and homogenizes the size distribution of the LMFP material. Moreover, the inferior rate and cycling performance of LMFP are mainly ascribed to the slower Li+ diffusion kinetics of Mn redox. A combination of experiments and DFT calculations shows that Na+ doping can increase the Li–O bond length, widen the Li+ diffusion channel, and decrease Li+ diffusion energy barriers, which can accelerate the Li+ diffusion rate and Mn redox kinetics, thereby improving the high-rate capability and cycling stability of Na+-doped samples. Besides, doped Na+ can not only act as pillars to stabilize the structure but also reduce Mn3+ content and Mn–Mn interactions to alleviate the Jahn–Teller effect, which also helps to improve the cycling performance of Na+-doped samples, wherein the Li0.98Na0.02Mn0.6Fe0.4PO4/C sample exhibits optimal rate and cycling performances. Its specific discharge capacity is 125.0 mAh g–1 at 5 C, and the capacity retention rate reaches 96.7% after 100 cycles at 1 C. Therefore, the Na+-doping strategy is believed to be an effective modification means to ameliorate the high-rate and cycling capabilities of olivine-based cathode materials.
研究领域:
材料科学
·
电化学
✓ 已验证
DOI
高影响因子
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
·
2024
·Vol. 31
·期 14
·21267-21278
·
IF 0
Zhao Dongling,Geng Linlin,Jia Yanfei,Wei Jianwen,Zhou Xiaobin,Liao Lei
High-temperature solid adsorbent Li 4 SiO 4 has received broad attention due to its high theoretical adsorption capacity, high regeneration capacity, and wide range of raw materials for preparation. In this paper, a Li 4 SiO 4 adsorbent was prepared by MCM-48 as the silica precursor and modified by doping with metal ions (Ca 2+ and Na + ) for high-temperature capture of low-concentration CO 2 . The results showed that the surface of the Ca-doped (or Na-doped) Li 4 SiO 4 adsorbent developed some particles that are primarily composed by Li 2 CaSiO 4 (or Li 3 NaSiO 4 ). Furthermore, the grains of the adsorbents became finer, effectively increasing the specific surface area and enhancing adsorption performance. Under 15 vol% CO 2 , the maximum CO 2 adsorption was 25.63 wt% and 32.86 wt% when the Ca 2+ doping amount was 0.06 and the Na + doping amount was 0.12, respectively. These values were both higher than the adsorption capacity before the metal ion doping. After 10 adsorption/desorption cycles, the adsorption capacity of Na-doped Li 4 SiO 4 increased by 9.68 wt%, while that of Ca-doped Li 4 SiO 4 decreased by 7.98 wt%. This difference could be attributed to the easy sintering of the Ca-containing adsorbent. Furthermore, a biexponential model was used to fit the CO 2 adsorption curve of the adsorbent in order to study the adsorption kinetics. Compared to the conventional Li 4 SiO 4 , the Ca/Na-doped adsorbent offers several advantages, such as a high CO 2 adsorption capacity and stable cycling ability.
研究领域:
材料科学
·
环境工程
·
化学工程
·
吸附技术
✓ 已验证
DOI
APPLIED SURFACE SCIENCE
·
2022
·
IF 7.392
Bowen Lu,Tai Zhang,Liqi Zhang,Yongqing Xu,Zewu Zhang,Fan Wu,Xiaoshan Li,Cong Luo
CeO 2 -based catalysts have been widely used in the CO 2 hydrogenation process. The oxygen vacancies on CeO 2 resulted from Na ion incorporation play a vital role in CO 2 conversion activity, the effect of Na + ion-doped in CeO 2 during CO 2 hydrogenation was rarely studied. In this work, the LN-CeO 2 catalysts with different n NaOH :n Ce ratios were prepared with liquid nitrogen(Liquid Nitrogen-CeO 2 , LN-CeO 2 ), and the effect of the n NaOH :n Ce ratio on the microstructure of the LN-CeO 2 catalysts were evaluated. The best CO 2 hydrogenation performance was achieved by LN-CeO 2 -100 with a CO production rate of 3.90 mol/g cat· h at 800 °C (100% CO selectivity). The kinetic results indicated that the CO 2 hydrogenation performance difference among these LN-CeO 2 catalysts resulted from the CO 2 activation process. Oxygen vacancies could enhance CO 2 activation on the surface of LN-CeO 2 , and oxygen vacancies displayed a linear correlation relationship with the Na content doped in LN-CeO 2 . The highest concentration of oxygen vacancies resulted from Na ion incorporated and lower CO 2 reaction order was closely related to CO 2 hydrogenation performance of LN-CeO 2 -100. These results will give insight into the Na effect on the CO 2 hydrogenation mechanism over CeO 2 .
研究领域:
催化化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
FUEL
·
2024
·
IF 6.7
Liangyong Chen,Rui Mao
Developing robust catalytic oxygen carriers (COC) to make Chemical-looping Oxidation Coupling of Methane (CL-OCM) economical and practical remains a big challenge. This work modified the Mn-based catalysts for co-feed OCM and tried to adapt them into CL-OCM process. COCs were specially designed with high faction of Mn-oxides to improve oxygen storage, with supports (pelletized from SiO 2 , MgO and TiO 2 ) of stable and porous structure to improve cyclic stability and to tune lattice oxygen reactivity, and with Na + dopant to improve conversion and selectivity. Among the COCs, Mn20Na2Si and Mn20Si (20 wt% Mn 2 O 3 supported on SiO 2 with/without 2.0 wt% Na 2 CO 3 dopants) exhibited excellent methane coupling activity. The averaged CH 4 conversion, C 2 selectivity and yield of Mn20Na2Si upon multiple redox cycles were 21.4 %, 79.6 % and 17.03 %, respectively. It showed improvements in C 2 selectivity and yield by 187 % and 163 % compared to Mn20Si. This work tried to establish the relationships between CL-OCM performance and lattice oxygen behaviors, since COC transports lattice oxygen to promote methane coupling as it performs as a catalyst during CL-OCM reduction. It is found that high C 2 -selectivity and CH 4 conversion are benefited from the constant oxygen transporting rate. Na + dopant improved the concentration of surface lattice oxygens, tuned the spatial arrangement of metal oxides, and stabilized the surface lattice oxygen in cyclic reactions. Due to Na + -doping, carbon deposition on Mn20Na2Si was avoided, and catalyst deactivation as well. Finally, a mechanism was developed to reveal how lattice oxygen species and their releasing rates affected surface reaction network, CH 4 conversion, C 2 selectivity and cyclic stability.
研究领域:
催化化学
·
能源化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF COLLOID AND INTERFACE SCIENCE
·
2024
·
IF 9.4
Shuya Yuan,Guowei Liu,Qingsheng Zhang,Taifeng Liu,Jianjun Yang,Zhongjie Guan
Element doping has been demonstrated as a useful strategy to regulate the band gap and electronic structure of photocatalyst for improving photocatalytic activity. Herein, ZnIn 2 S 4 (ZIS) nanosheets were doped with alkali metal ions (Li + , Na + or K + ) by a simple solution method. Experimental characterizations reveal that alkali metal ions doping reduce the band gap, raise the conduction band position, and improve surface hydrophilicity of ZIS. In addition, theoretical calculations show that Na doping increases the electron density at valence band maximum and surrounding S atom, which is conducive to produce more electrons and effective utilization of electrons, respectively. Benefited from above factors, Na-doped ZIS (Na-ZIS) shows the highest photocatalytic hydrogen evolution performance. Furthermore, CoSe 2 cocatalyst is loaded on the surface of Na-ZIS (CS/Na-ZIS), which further improve the charge separation and prolong the lifetime of charges. As a result, the optimized CS/Na-ZIS shows a H 2 evolution rate of 4525 μmol·g −1 ·h −1 with an apparent quantum efficiency of 27.5 % at 420 nm, which are much higher than that of pure ZIS. This study provides an in-depth understanding of the synergistic effect of Na doping and CoSe 2 cocatalyst in ameliorating photocatalytic activity.
研究领域:
材料科学
·
催化
·
能源材料
·
光化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
OPTICS EXPRESS
·
2023
·Vol. 31
·期 15
·25298-25306
·
IF 3.8
Haoming Wei,Haoming Wei,Tingyu Si,Fan Xu,Wuyang Fan,Tengzhou Yang,Bingqiang Cao,Fangying Juan,Jun Xu,Yangqing Wu
Double perovskites without lead element have attracted great attention in recent years. Further increasing the photoluminescence quantum yield of lead-free double perovskites is necessary for their potential applications. In this work, Na+ doped Cs2SnI6 nanocrystals were synthesized by hot injection method. It was displayed that all the NCs have uniform hexagonal shape with good crystallization. Energy dispersing spectroscopy and X-ray photoelectron spectroscopy proves the Na+ ions were doped in the lattice of perovskite structure. The photoluminescence intensity of doped NCs is increased by 2.7-fold than that of pure NCs. A maximum photoluminescence quantum yield of 72% is obtained. The luminous mechanism was investigated by femtosecond transient absorption spectrum and a self-trap emission was proved by the observation of ground state bleaching and photo-induced absorption signals.
研究领域:
材料科学
·
纳米技术
·
光学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）