共查询到20条相似文献，搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2019,44(16):8109-8120
Anatase titanium dioxide (TiO2) nanocrystals with different percentages (up to 95%) of exposed {101} facet and different concentration ratios of bulk single-electron-trapped oxygen vacancies (SETOVs) to surface oxygen vacancies (SOVs) were prepared by alcohol-thermal method with nanotube titanic acid as the precursor in combination with solid-state reduction by NaBH4. The as-prepared TiO2 nanocrystals were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, electron spin resonance spectroscopy, and ultraviolet–visible light spectrometry. The effects of the percentage of crystal facets and the concentration ratio of bulk SETOVs/SOVs on the photocatalytic hydrogen production rate of TiO2 nanocrystals were investigated with positron annihilation lifetime spectroscopy as well as photocurrent test. Findings indicate that the percentage of the exposed {101} facets of the as-prepared TiO2 nanocrystals and their concentration ratios of bulk SETOVs/SOVs can be well tuned by properly adjusting the amount of NaBH4 and the reduction reaction time as well. Increasing percentage of the {101} facet of anatase TiO2 nanocrystals contributes to improving their photocatalytic hydrogen production activity, because the {101} facets of the anatase TiO2 nanocrystals possess enriched electrons and can act as the reduction sites to enhance the reduction reaction of H+ affording H2 in the sacrifice system of splitting water. Both the bulk SETOVs and SOVs contribute to the improvement of the light absorption while SOVs can facilitate the separation of photogenerated charges, thereby adding to the photocatalytic activity. However, the bulk SETOVs and excessive SOVs are also the combination centers of photogenerated charges, which means it is essential to maintain a suitable concentration ratio of the bulk SETOVs/SOVs so as to enhance the light absorption and achieve the best separation efficiency of photogenerated charges and achieve the best photocatalytic activity for hydrogen production. Particularly, when anatase TiO2 nanocrystal with a high percentage (95%) of exposed {101} facet is reduced by NaBH4 at a mass ratio of 2: 1 for 20 min, the resultant reduced H-TiO2 nanocrystal (denoted as H-TiO2-R20(2:1)) provides the highest photocatalytic hydrogen productive rate. Furthermore, the combination of 0.5% Pt/H-TiO2-R20(2:1) with 0.5% Pt/WO3 can split water to simultaneously produce H2 and O2, showing promising potential for splitting water affording hydrogen and oxygen. 相似文献
2.
Lulu Gao Dr Chongyang Tang Dr Jiangchao Liu Lanli He Dr Hongbo Wang Dr Zunjian Ke Prof Wenqing Li Prof Changzhong Jiang Dr Dong He Dr Li Cheng Prof Xiangheng Xiao 《ENERGY & ENVIRONMENTAL MATERIALS》2021,4(3):392-398
Despite the tremendous efforts devoted to enhancing the activity of oxygen evolution reaction (OER) catalysts, there is still a huge challenge to deeply understand the electronic structure characteristics of transition metal oxide to guide the design of more active catalysts. Herein, Fe3O4 with oxygen vacancies (Fe3O4-Vac) was synthesized via Ar ion irradiation method and its OER activity was greatly improved by properly modulating the electron density around Fe atoms. The electron density of Fe3O4-Vac around Fe atoms increased compared to that of Fe3O4 according to the characterization of synchrotron-based X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS) spectra, and density functional theory (DFT) calculation. Moreover, the DFT results indicate the enhancement of the desorption of HOO* groups which significantly reduced the OER reaction barrier. Fe3O4-Vac catalyst shows an overpotential of 353 mV, lower than that of FeOOH (853 mV) and Fe3O4 (415 mV) at 10 mA cm−2, and a low Tafel slope of 50 mV dec−1 in 1 M KOH, which was even better than commercial RuO2 at high potential. This modulation approach provides us with valuable insights for exploring efficient and robust water-splitting electrocatalysts. 相似文献
3.
《International Journal of Hydrogen Energy》2023,48(35):13123-13138
Herein, the surface properties of graphitic carbon nitride (GCN) with sulphur(S), boron (B) and oxygen (O) dopants were improved. The heteroatom-doped metal-free GCN exhibited both rich surface functional groups and a carbon defect structure. These metal-free catalysts were used to obtain hydrogen (H2) from the sodium borohydride (SB) methanolysis for the first time. Compared to GCN, S, B, and O doped GCN catalyst obtained showed a 2.2-fold improvement in H2 production. HGR value obtained with B, O and S doped GCN (10 mg) via SB of 2.5% was 9166 ml min −1g−1. XPS, SEM-EDX, TEM, FTIR, and XRD analyses were used for the structural properties of catalysts. The activation energy (Ea) for B, O and S doped GCN was 28.89 kJ mol−1. 相似文献
4.
Shipra Jain Jyoti Shah Nainjeet Singh Negi Chhemendra Sharma Ravinder Kumar Kotnala 《国际能源研究杂志》2019,43(9):4743-4755
Recent increase in energy demand and associated environmental degradation concern has triggered more research towards alternative green energy sources. Eco‐friendly energy in facile way has been generated from abundantly available iron oxides using only few microliters of water without any external energy source. Hydroelectric cell (HEC) compatible to environment benign, low cost oxygen‐deficient mesoporous hematite nanoparticles has been used for splitting water molecules spontaneously to generate green electricity. Hematite nanoparticles have been synthesized by coprecipitation method. Chemidissociated hydroxyl group presence on hematite surface has been confirmed by infrared spectroscopy (IR) and X‐ray photoelectron spectroscopy (XPS). Surface oxygen vacancies in nanostructured hematite have been identified by transmission electron microscopy (TEM), XPS, and photoluminescence (PL) measurement. Hematite‐based HEC delivers 30 mA current with 0.92 V emf using approximately 500 μL water. Maximum off‐load output power 27.6 mW delivered by 4.84 cm2 area hematite‐based HEC is 3.52 times higher than reported 7.84 mW power generated by Li‐magnesium ferrite HEC. Electrochemistry of HEC in different irreversible polarization loss regions has been estimated by applying empirical modeling on V‐I polarization curve revealing the reaction and charge transport mechanism of cell. Tafel slope 22.7 mV has been calculated by modeling of activation polarization overvoltage region of 0.11 V. Low activation polarization indicated easy charge/ion diffusion and faster reaction kinetics of Ag/Zn electrode owing to lesser energy barrier at interface. Dissociated H3O+ ions diffuse through surface via proton hopping, while OH? ions migrate through interconnected defective crystallite boundaries resulting into high output cell current. 相似文献
5.
Nowadays, the development of fuel cell is getting more and more inseparable from the production of hydrogen. Long-chain hydrocarbons steam reforming is a feasible way for hydrogen supply. Herein, various nickel-ceria-praseodymium (Ni-Ce-Pr) catalysts have been prepared by a sol-gel method. Multiple parameters during catalyst preparation, including the amount of Ni, the content of doped Pr and the calcination temperature, were systematically studied for tuning the catalytic performance for n-dodecane steam reforming in a fixed-bed reactor under 15 mL/gcat·h at 600°C and water-to-carbon molar ratio of 2 at 0.1 MPa. Reaction data showed that both the amount of Ni and the content of doped Pr will greatly affect the n-dodecane conversion and hydrogen production. Additionally, the calcination temperature during catalyst preparation showed a big influence on its performance for n-dodecane steam reforming. After optimization, 10Ni-CePr2-600 exhibits the highest activity and stability for n-dodecane steam reforming, accompanying with the lowest rate of coke deposition (0.015 gc/gcat·h). The structure and oxygen vacancy of the catalyst was characterized by H2-TPR, Raman, and X-ray photoelectron spectroscopy (XPS). The superior activity and stability of 10Ni-CePr2-600 are ascribed to the strong interaction between NiO and support along with abundant oxygen vacancies in the Pr-doped ceria. 相似文献
6.
《International Journal of Hydrogen Energy》2020,45(41):21848-21857
The development of superior catalysts for preferential oxidation of CO has always maintained challenging in heterogeneous catalysis. Herein it is found that the Pt0.05/CuO–CeO2 catalyst exhibited high activity and selectivity for preferential oxidation of CO at working temperature of proton-exchange membrane fuel cells (~80 °C). The studies indicate that the presence of platinum and cerium promote the generation of oxygen vacancy and the dissociation of O2 molecules. Meanwhile, the introduction of platinum facilitates the reduction of copper and cerium species as well as enhances the quantity of lattice oxygen. The timely update of lattice oxygen promotes CO oxidation with the help of oxygen vacancy. The finding may provide new ideas for developing the excellent ternary catalyst for preferential oxidation of CO at the proton-exchange membrane fuel cells working temperature. 相似文献
7.
《International Journal of Hydrogen Energy》2022,47(60):25443-25453
The “hydroxyl-oxygen vacancy model” was of great importance for the catalytic and physicochemical properties of metal oxides. Here, we proposed a simple method to construct a hydroxyl-oxygen vacancy model for one-step reduction of palladium chloride through ascorbic acid rich in hydroxyl, loaded on rod, spherical, nanoparticles and cubic CeO2, to achieve the Ce4+/Ce3+ transition and the generation of Pd NPs. The surface-loading Pd ions activated the lattice oxygen of CeO2, and promoted the overflow of reverse oxygen at the Pd–O–Ce interface. The increasing in Ce3+ occupancy altered the reduction performance, oxygen vacancy number and active Pd valence state of the catalyst, and greatly contributed to the response and recovery times. Among the obtained sensors, the 0.50 wt % Pd/CeO2–C/R sensor show a response amplitude of 190/196% to 1000 ppm H2 at 120 °C with a response/recovery time of only 1/3 s. These excellent results are mainly attributed to the chemisorbed oxygen and Ce3+ after ascorbic acid reducing Pd are found to be 4.84 and 1.57 times higher than pure CeO2. The hydroxyl-oxygen vacancy model may open up a new avenue for detecting hydrogen sensing. 相似文献
8.
9.
《International Journal of Hydrogen Energy》2019,44(46):25265-25275
In the present study, the reduction of NO by two activated carbons without and loaded with Fe based catalysts was studied at 300 °C using a fixed-bed reactor. The activated carbon samples impregnated with and without the catalysts were characterized using TGA, SEM, gas adsorption, ICP-AES, XPS and XRD. The experimental results showed that neither of the raw activated carbons achieved the required denitrification performance. However, compared with coal derived activated carbon (C0), biomass derived activated carbon (B0) performed better. The denitrification efficiency improved with the O2 content in the flue gas, achieved a maximum approximately at 3% O2, and then decreased with further increase in the O2 content. The effect of the metals loaded and addition amount of the catalysts was then examined in detail with the biomass derived activated carbon. At the same dosage of catalysts, the biomass derived activated carbon impregnated with K ions was apparently more efficient than it counterpart loaded with Fe ions. A higher addition rate of Fe was required in order to be efficient in NO conversion. Addition of K was further found to significantly improve the NO conversion efficiency of the biomass activated carbon loaded with 3% Fe which otherwise showed a sharp premature decrease in NO conversion efficiency immediately after the flue gas was introduced. Finally the effects contributing to the synergetic effect of Fe and K are discussed. 相似文献
10.
钙钛矿型催化剂La1-xKxCoO3-λ的表征特性及对柴油机尾气中NOx催化性能的研究 总被引：1，自引：0，他引：1
采用柠檬酸络合燃烧法制备了K~ 部分取代La~(3 )的La_(1-x)K_xCoO__(3-λ)钙钛矿型催化剂,使用XRD、STEM和化学分析等方法对催化剂的组成和结构进行了表征,并利用程序升温反应研究了催化剂对柴油机尾气中NO_x的净化催化活性．实验结果表明,K~ 部分取代A位La~(3 )会导致复合氧化物La_(1-x)K_xCoO_(3-λ)的晶体结构及组成发生变化．当取代量x≤0．3时,La_(1-x)K_xCoO_(3-λ)为单相的钙钛矿型复合氧化物;x≥0．4时,催化剂样品中出现CO_3O_4,且其含量随着取代量x的增大而增大．La_(1-x)K_xCoO_(3-λ)催化剂对于柴油机尾气中NO_x的净化有较好的催化活性;当x=0．3时,催化剂表面氧空位量最大,对柴油机尾气中NO_x的净化效率最高,在450℃时可达50%．在催化剂作用下,柴油机排放颗粒物(PM)的存在提高了NO_x的净化效率． 相似文献
11.
《International Journal of Hydrogen Energy》2022,47(44):19016-19026
In the study, metal-free boron and oxygen incorporated graphitic carbon nitride (B and O doped g-C3N4) with carbon vacancy was successfully prepared and applied as a catalyst to the dehydrogenation of sodium borohydride (NaBH4) in methanol for the first time. The hydrogen generation rate (HGR) value was found to be 11,600 mL min?1g?1 by NaBH4 of 2.5%. This is 2.53 times higher than the g-C3N4 catalyst without the addition of B and O. The obtained activation energy was 25.46 kJ mol?1. X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), energy dispersive X-Ray analyser (EDX), Transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR) analyses for characterization were performed. A possible mechanism of H2 production from the reaction using metal-free B and O doped g-C3N4 catalyst with carbon vacancy has been proposed. This study showed that g-C3N4 and its composites with doping atoms can be used effectively in H2 production by NaBH4 methanolysis. 相似文献
12.
为了研究MnO_x-CeO_2复合氧化物催化氧化柴油机NO的性能,采用溶胶凝胶法制备了不同Mn/Ce摩尔比的xMn10Ce/γ-Al_2O_3(x=5,6,7,8)催化剂。利用X射线衍射(X-ray diffraction,XRD)、X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)和H_2程序升温还原(H_2temperature programmed reduction,H_2-TPR)技术分别对其物相结构、元素价态及还原性能进行了表征。结果表明:CeO_2晶粒尺寸随Mn含量增加而逐渐变大,同时添加适量的Mn也有利于提高催化剂中Mn~(4+)的数量,从而促进NO氧化;当x=6时,催化剂的氧化还原性能最好。最后,基于模拟气试验平台考察了不同Mn/Ce比对xMn10Ce/γ-Al_2O_3催化剂氧化NO性能的影响。结果表明:在350℃时,NO浓度达饱和所需时间和反应速率与Mn添加量呈非线性关系;在250~450℃范围内,6Mn10Ce/γ-Al_2O_3的NO氧化性能最好,其NO浓度在350℃时最先达到稳定,仅需4min,但在450℃时则延长至6min,这主要是受热力学平衡及随反应进行活性氧数量及氧空位逐渐饱和共同作用的结果。 相似文献
13.
Yohan Ko Taemin Kim Chanyong Lee Changhyun Lee Yong Ju Yun Yongseok Jun 《ENERGY & ENVIRONMENTAL MATERIALS》2023,6(2):e12347
Electron transport layer (ETL) is pivotal to charge carrier transport for PSCs to reach the Shockley–Queisser limit. This study provides a fundamental understanding of heterojunction electron transport layers (ETLs) at the atomic level for stable and efficient perovskite solar cells (PSCs). The bilayer structure of an ETL composed of SnO2 on TiO2 was examined, revealing a critical factor limiting its potential to obtain efficient performance. Alteration of oxygen vacancies in the TiO2 underlayer via an annealing process is found to induce manipulated band offsets at the interface between the TiO2 and SnO2 layers. In-depth electronic investigations of the bilayer structure elucidate the importance of the electronic properties at the interface between the TiO2 and SnO2 layers. The apparent correlation in hysteresis phenomena, including current density–voltage (J–V) curves, appears as a function of the type of band alignment. Density functional theory calculations reveal the intimate relationship between oxygen vacancies, deep trap states, and charge transport efficiency at the interface between the TiO2 and SnO2 layers. The formation of cascade band alignment via control over the TiO2 underlayer enhances device performance and suppresses hysteresis. Optimal performance exhibits a power conversion efficiency (PCE) of 23.45% with an open-circuit voltage (Voc) of 1.184 V, showing better device stability under maximum power point tracking compared with a staggered bilayer under one-sun continuous illumination. 相似文献
14.
《International Journal of Hydrogen Energy》2022,47(50):21329-21343
One-dimensional (1D) nanofiber structure of electrocatalyst has attracted increasing attention in oxygen evolution/reduction reactions (OER/ORR) owing to its unique structural properties. Here, MIL-53(Fe) and Ni(NO3)2·6H2O are incorporated into the electrospun carbon nanofibers (CNFs) to prepare the nickel-iron spinel-based catalysts (Fe2O3/NiFe2O4@CNFs) with 1D and porous structure. The marked Fe2O3/NiFe2O4@CNFs-2 catalyst has a tube diameter of approximately 300 nm, a high surface area of 282.4 m2 g?1 and a hydrophilic surface (contact angle of 16.5°), which obtains a promising bifunctional activity with ΔE = 0.74 V (E1/2 = 0.84 V (ORR) and Ej10 = 1.58 V (OER)) in alkaline media. Fe2O3/NiFe2O4@CNFs-2 has a higher catalytic stability (93.35%) than Pt/C (89.36%) for 30,000 s tests via an efficient 4e? ORR pathway. For OER, Fe2O3/NiFe2O4@CNFs-2 obtains a low overpotential of 350 mV and a high Faraday efficiency of 92.7%. NiFe2O4 (Ni2+ in tetrahedral position) relies on its variable valence states (NiOOH and/or FeOOH) to obtain good catalytic activity and stability for OER, while CNFs wrap/protect the active components (Fe–N and graphic N) in the carbon skeleton to effectively improve the charge transfer (conductivity), activity and stability for ORR. Porous 1D nanofiber structure provides abundant smooth pathways for mass transfer. It indicates that the bimetallic active substances can promote bifunctional activity by synergistically changing the oxide/spinel interface structure. 相似文献
15.
Xun Li;Tian Tan;Wei Ji;Wanling Zhou;Yuwen Bao;Xiaohong Xia;Zhangfan Zeng;Yun Gao; 《ENERGY & ENVIRONMENTAL MATERIALS》2024,7(3):e12624
Development of metal oxide semiconductors-based methane sensors with good response and low power consumption is one of the major challenges to realize the real-time monitoring of methane leakage. In this work, a self-assembled mulberry-like ZnO/SnO2 hierarchical structure is constructed by a two-step hydrothermal method. The resultant sensor works at room temperature with excellent response of ~56.1% to 2000 ppm CH4 at 55% relative humidity. It is found that the strain induced at the ZnO/SnO2 interface greatly enhances the piezoelectric polarization on the ZnO surface and that the band bending results in the accumulation of chemically adsorbed O2− ions close to the interface, leading to significant improvement in the sensing performance of the methane gas sensor at room temperature. 相似文献
16.
A comparative study of vegetable oil methyl esters (biodiesels) 总被引：1，自引：0，他引：1
In the present study, rubber seed oil, coconut oil and palm kernel oil, which are locally available especially in Kerala (India), are chosen and their transesterification processes have been investigated. The various process variables like temperature, catalyst concentration, amount of methanol and reaction time were optimized. Biodiesel from rubber seed oil (with high free fatty acid) was produced by employing two-step pretreatment process (acid esterification) to reduce acid value from 48 to 1.72 mg KOH/g with 0.40 and 0.35 v/v methanol-oil ratio and 1.0% v/v H2SO4 as catalyst at a temperature of 63(±2) °C with 1 h reaction time followed by transesterification using methanol-oil ratio of 0.30 v/v, 0.5 w/v KOH as alkaline catalyst at 55(±2) °C with 40 min reaction time to yield 98-99% biodiesel. Coconut oil and palm oil, being edible oils, transesterification with 0.25 v/v methanol-oil ratio, 0.50% w/v KOH as at 58(±2) °C, 20 min reaction time for coconut oil and 0.25% v/v methanol-oil ratio, 0.50% w/v KOH as alkaline catalyst at 60(±2) °C for palm kernel oil will convert them to 98-99% biodiesel. The brake thermal efficiency of palm oil biodiesel was higher with lower brake specific fuel consumption, but rubber seed oil biodiesel(ROB) showed less emission (CO and NOx) compared to other biodiesels. 相似文献
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18.
Qianqian Bai Jiahui Sun Wei Xu Ruiping Wei Guomin Xiao 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(10):1273-1278
The Cyanobacteria was catalytically pyrolyzed in methanol atmosphere using magnesium-aluminum layered double oxide/ZSM-5 composites (MgAl-LDO/ZSM-5) as a catalyst. The largest liquid yield of 67.68% was obtained in methanol atmosphere, which was much higher than that obtained without methanol under same reaction condition. The Gas chromatography-Mass spectrometer data proved that the organics phase contained less O-compounds and N-compounds and more aromatic compounds. And the ultimate analysis results showed that this bio-oil had much higher HHV values and lower O/C molar ratio. The co-processing methanol atmosphere and bifunctional catalyst would be a promising means for improving the quality of bio-oil. 相似文献
19.
我国生物柴油产业发展展望 总被引：19，自引：0，他引：19
生物柴油是对汽车、环境生态和人友好的可再生能源。本文着重论述了发展生物柴油产业对我国保护生态环境、增强国家石油安全、推动农业结构调整、增加农民收入、促进农村和国家经济发展的重要作用。本文介绍了世界各国和我国生物柴油产业发展现状,并根据产业原料资源的分析预测,展望了我国生物柴油产业发展潜力和未来十年分三阶段发展的光明前景。最后,本文对产业发展提出了建议,对产业的未来充满信心。 相似文献
20.
Quanhong Ma Dongdong Chen Lingfei Wei Quanhao Shen Zhongxiang Ji Yong Chen 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(2):200-206
This paper describes catalytic hydrogenation liquefaction of rice straw over metal (Ni, Co, and Cu)-modified CeO2 catalysts for bio-oil production. The results show that the highest rice straw conversion (89.08%) and bio-oil yield (66.7%) were obtained over Ni/CeO2 catalyst. The bio-oil contains mainly phenols, high-value-added, and widely used chemicals. Furthermore, metal-modified CeO2 catalysts can significantly influence the components of bio-oil with the highest percentage of C7-C10 compounds. This work thus demonstrates that metal/CeO2 catalysts can be effective in improving the bio-oil yield and selectivity in hydro-liquefaction of rice straw into bio-oil. 相似文献