基于槽式聚光的光热反应与集热协同实验研究

设计一种全光谱太阳能分级分质利用系统进行光热协同反应与集热一体化实验研究。该系统通过光热协同催化材料将太阳光中紫外及部分可见波段光的能量转化为化学能进行储存,并利用系统中的集热材料将太阳光中部分可见及红外波段的光能转化为热能进行储存,从而实现对全光谱太阳能的综合利用。实验以光热协同分解水制氢为目标反应,利用导热油进行集热。结果表明,在反应材料表面温度为414℃的条件下,氢气产量为15.65μmol/g,系统集热效率可达43.61%。

基于AuMgO@TiO_(2)球壳的光热协同反应耦合集热研究

实验室前期搭建太阳能有序转化系统,利用太阳辐射高频波段合成碳氢燃料,低频波段转化为高品质热能。基于该系统,制备Au和MgO负载的TiO_(2)球壳材料,进行光热协同反应转化CO_(2)和H_(2)O,同时结合集热层利用导热油集热,结果表明,H_(2)、CH_(4)、CO产量分别为30.1、3.2、30.9μmol/g,系统集热效率可达39.85%。实验结合表征显示,球壳结构、Au和MgO共负载可提高材料光吸收,增强光热性能,降低电子空穴对复合率,产生氧空位,促进光热协同反应还原CO_(2)。

光热催化CO_(2)还原制甲酸研究进展

CO_(2)资源化利用是实现“碳达峰碳中和”目标不可或缺的环节。将CO_(2)催化转化为甲酸是一种有效且最为原子经济的路径,但因CO_(2)热力学性质稳定,导致其不易活化,反应转化率低。为了在温和条件下得到更高的甲酸产率,将光催化与热催化结合。光热催化主要体现在光活化上,通过激发载流子,调控电子注入位置和吸附位点有效活化CO_(2),热能则增强反应物CO_(2)的吸附、电荷转移和反应速率,激活热活性位点,结合光催化的低能耗、反应条件温和与热催化高效率的优势提高甲酸产率及选择性。目前,光热催化CO_(2)还原制甲酸的主要挑战在于CO_(2)固有的化学稳定性使得CO_(2)转化率低、产物不可控、选择性差等。基于目前对光热催化CO_(2)转化技术的需求,分别介绍了光催化、热催化、光热催化的原理、优势及存在的问题,重点从催化剂改性、反应条件、反应器选择方面综述了光热催化CO_(2)还原制甲酸过程中提高CO_(2)转化率和甲酸选择性的策略,其中重点探讨对于催化剂的改性,包括提高电子-空穴分离程度、调控暴露面比例以及提高CO_(2)的吸附,并阐述了光热催化CO_(2)还原制甲酸需重点攻克的问题。未来研究应综合考虑反应器选择与催化剂设计,通过反应条件的优化,实现高产率甲酸的生产以及光热催化大规模工业应用。

基于光热协同反应的太阳能有序转化系统

提出一种将光热协同太阳能燃料制备与集热技术相结合的新型太阳能有序转化综合利用系统。该系统通过光热协同反应将太阳能中紫外可见波段能量以化学能形式存储,并利用集热技术转化部分可见及红外波段能量为中温热能。采用CO;还原为光热协同目标反应,导热油为传热工质进行系统运行实验,实验结果表明:光热协同反应温度为290℃,产物CO产率为5.80μmol/g-cat,集热片温度为320℃,通过导热油吸热量计算得集热子系统辐射能量利用效率为59.7%。

Regulating crystal phase of TiO_(2) to enhance catalytic activity of Ni/TiO_(2) for solar-driven dry reforming of methane

Ni/TiO_(2) catalyst is widely employed for photo-driven DRM reaction while the influence of crystal structure of TiO_(2) remains unclear.In this work,the rutile/anatase ratio in supports was successfully controlled by varying the calcination temperature of anatase-TiO_(2).Structural characterizations revealed that a distinct TiO_(x) coating on the Ni nanoparticles(NPs)was evident for Ni/TiO_(2)-700 catalyst due to strong metal-support interaction.It is observed that the TiOx overlayer gradually disappeared as the ratio of rutile/anatase increased,thereby enhancing the exposure of Ni active sites.The exposed Ni sites enhanced visible light absorption and boosted the dissociation capability of CH4,which led to the much elevated catalytic activity for Ni/TiO_(2)-950 in which rutile dominated.Therefore,the catalytic activity of solar-driven DRM reaction was significantly influenced by the rutile/anatase ratio.Ni/TiO_(2)-950,characterized by a predominant rutile phase,exhibited the highest DRM reactivity,with remarkable H_(2) and CO production rates reaching as high as 87.4 and 220.2 mmol/(g·h),respectively.These rates were approximately 257 and 130 times higher,respectively,compared to those obtained on Ni/TiO_(2)-700 with anatase.This study suggests that the optimization of crystal structure of TiO_(2) support can effectively enhance the performance of photothermal DRM reaction.

Solar-heating boosted catalytic reduction of CO_(2） under full-solar spectrum

Catalytic converting CO2 into fuels with the help of solar energy is regarded as‘dream reaction’,as both energy crisis and environmental issue can be mitigated simultaneously.However,it is still suffering from low efficiency due to narrow solar-spectrum utilization and sluggish heterogeneous reaction kinetics.In this work,we demonstrate that catalytic reduction of CO2 can be achieved over Au nanoparticles(NPs)deposited rutile under full solar-spectrum irradiation,boosted by solar-heating effect.We found that UV and visible light can initiate the reaction,and the heat from IR light and local surface-plasmon resonance relaxation of Au NPs can boost the reaction kinetically.The apparent activation energy is determined experimentally and is used to explain the superior catalytic activity of Au/rutile to rutile in a kinetic way.We also find the photo-thermal synergy in the Au/rutile system.We envision that this work may facilitate understanding the kinetics of CO2 reduction and developing feasible catalytic systems with full solar spectrum utilization for practical artificial photosynthesis.

Pyroelectricity effect on photoactivating palladium nanoparticles in PbTiO3 for Suzuki coupling reaction

Combining microwave radiation with photocatalytic systems is a promising method to inhibit photogenerated electron-hole recombination and enhance the photocatalytic reaction performance. In this study, we have designed Pd/Pb TiO3 catalysts that can use both microwave fields and photocatalysis. Benefiting from the synergistic effect of microwave field and UV light, the Pb TiO3 crystals convert thermal energy into electrical energy via the pyroelectricity effect, generating positive and negative charges(q+ and q-), while Pd nanoparticles significantly improve the quantum efficiency of the photocatalytic process. The composite catalyst significantly enhances the reaction rate and selectivity of the model Suzuki coupling reaction performed with bromobenzene. Microwave fields can directly act on chemical systems, promoting or changing various chemical reactions in unique ways.

Low-temperature phase transitions of sodium aluminate solutions

A series of low-temperature phase transitions of sodium aluminate solutions were studied by differential scanning calorimetry (DSC) and Raman spectroscopy. The results indicate that NaOH concentration is a primary impact factor for the binary eutectic point and ice melting temperature of sodium aluminate solutions with low NaOH concentration. In addition, the phase transition process of sodium aluminate solutions with low NaOH concentration from 123.15 to 283.15 K is divided into four steps: non-crystal to crystal, ternary eutectic reaction, binary eutectic reaction and ice melt. The projection phase diagram of NaOH-Al(OH)3-H2O system at low temperature was plotted, in which the ternary eutectic temperature for sodium aluminate solutions is 183.15 K.

Laser Cleaning of Mirror Surface for Optical Diagnostic Systems of the International Thermonuclear Experimental Reactor

The development of cleaning optics and deposition-mitigating techniques is a key factor in the construction and operation of optical diagnostics in ITER. The cleaning of optical surface by pulsed radiation from a fiber laser is an effective method that can recover optical properties of the mirror surface. The possibility of cleaning metallic mirrors from films with complex composition by pulsed radiation from a fiber laser has been experimentally researched. It has been shown that the high initial reflection characteristics of optical elements can be recovered by choosing regimes of radiation effect on the deposited surface. Efficient cleaning is ensured by radiation with the power density of less than 107 W/cm2. At this relatively low power density, pollutions are removed in a solid phase and the thermal effect on the mirror is insignificant. Preliminary experiments of the metal mirrors cleaning by fiber laser radiation have demonstrated the possibility of hardware implementation techniques.

Different Carbon Fractions in Soils and Their Relationship with Trace Elements Content

Luvisols, Stagnogleys and Cambisols, although less fertile, are used intensively for mixed farming, grazing and as forestland. Therefore we aimed our study at determination of total organic carbon （TOC） content, humic substances （HS） content, humic acids （HA） content, fulvic acids （FA）, hot water extractable carbon （Chw） content and content total and labile trace elements content. Humic substances quality was assessed by HA/FA ratio and by coloured indexes measured in ultraviolet and visible UV-VIS spectral range. The total and labile contents of Zn, Cd, Cu, Co, Pb, Mo and Se were determined by flame or electro-thermal atomic absorption spectrometry after extraction of the soil samples in the aqua regia （total content） and in the solution of 0.01 M CaCI2. Total and labile trace elements content was correlated with determined carbon fractions and soil reaction. Results showed that studied soils content low amount of TOC and had low quality of humic substances. HA/FA ratio was less than 1 and colour indexes were higher than 4. All determined carbon fractions correlated with labile form of Zn and Cd. Correlation between soil reaction and total zinc content was found. Significant effect of humic substances content on to water-soluble forms of heavy metals was detected.

基于锌锗二元氧化物的光热协同分解CO2研究

本工作为非Ti基光热协同材料研究,使用溶液沉淀法制备了ZnO/Zn2GeO4复合材料(Z/ZGO)应用于光热协同分解CO2.使用透射电子显微镜(TEM)、X射线衍射技术(XRD)、紫外可见漫反射光谱(UV-Vis DRS)、X射线光电子能谱(XPS)等表征手段对材料的形貌、光响应以及氧空位对反应的影响进行研究.锌锗二元氧化物复合材料综合两种半导体的优势,形成异质结,扩展了材料光谱响应范围,提高了材料氧空位形成能力,使得CO产率提高至单纯ZnO样品的5.55倍,并具有较好的循环稳定性.对扩展光热协同催化材料体系,进一步深化光热协同反应机理以及提升反应产率具有一定的前瞻和指导作用.

One-step synthesis of fluorescent hydroxyls-coated carbon dots with hydrothermal reaction and its application to optical sensing of metal ions

Carbon dots (CDs) with average diameter of 3.1 ± 0.5 nm were facilely synthesized with candle soot through hydrothermal reaction in sodium hydroxide aqueous solution. The as-prepared CDs were covered with a lot of hydroxyls, possessed properties of good water-solubility, anti-photobleaching, salt tolerance, and low cytotoxicity, and had a fluorescence quantum yield (QY) of about 5.5%. The fluorescence of the hydroxyls-coated CDs could be selectively quenched by metal ions such as Cr3+, Al3+ and Fe3+, which is because these metals can easily combine with the hydroxyl groups on the surface of CDs and induce aggregation of hydroxyls-coated CDs. Experiments showed that the quenching of Cr3+ had a Sterm-Volmer constant of 1.03 × 107 M-1 with a liner range of 1.0-25.0 μM and detection limit of 60 nM (3σ).

An integrated thermoelectric-assisted photoelectrochemical system to boost water splitting

Common solar-driven photoelectrochemical(PEC) cells for water splitting were designed by using semiconducting photoactive materials as working photoelectrodes to capture sunlight. Due to the thermodynamic requirement of 1.23 eV and kinetic energy loss of about 0.6 eV, a photo-voltage of 1.8 V produced by PEC cells is generally required for spontaneous water splitting. Therefore, the minimum bandgap of1.8 eV is demanded for photoactive materials in single-photoelectrode PEC cells, and the bandgap of about 1 eV for back photoactive materials is appropriate in tandem PEC cells. All these PEC cells cannot effectively utilize the infrared light from 1250 to 2500 nm. In order to realize the full spectrum utilization of solar light, here, we develop a solar-driven PEC water splitting system integrated with a thermoelectric device. The key feature of this system is that the thermoelectric device produces a voltage as an additional bias for the PEC system by using the temperature difference between the incident infrared-light heated aqueous electrolyte in the PEC cell as the hot source and unirradiated external water as the cold source. Compared to a reference PEC system without the thermoelectric device, this system has a significantly improved overall water splitting activity of 1.6 times and may provide a strategy for accelerating the application of full spectrum solar light-driven PEC cells for hydrogen production.

Numerical Investigation of the Thermal Response to Skin Tissue during Laser Lipolysis

Laser lipolysis can effectively treat obesity and its associated diseases, such as hypertension, fatty liver, and hyperlipidemia. However, currently available invasive laser lipolysis, which transmits laser to a fiber-optic catheter inserted into the subcutaneous tissue for irradiation through an incision, may cause hematomas, infections, and empyrosis. The current study presents a novel, noninvasive approach for laser lipolysis, which directly irradiates the intact skin surface without an incision and preferentially targets adipose tissue at the near-infrared band. High laser energy is necessary to damage adipocytes; however, this may carbonate and burn the dermis. Therefore, the introduction of skin cooling is essential to avoid unwanted hyperthermal injury and improve the threshold of radiant exposure. In the current study, we investigated a novel noninvasive approach assisted with skin cooling by establishing a homogeneous multi-layer skin model. In this method, light propagation in the skin was simulated by using the Monte Carlo method. Skin cooling was employed before laser irradiation to protect the epidermis from thermal damage, which was treated as a boundary condition based on Newton's law. The numerical results showed that the photons were deposited in the adipose layer more than in the other layers. Laser can effectively destroy adipose tissue at an energy density of >200 J/cm^2 at 1210 nm wavelength, whereas at least 300 J/cm^2 is required at 1064 nm to achieve the same effect. In this experiment, at >5 s pulse width, the selectivity of adipose was not obvious. Moreover, the results indicated that 60 ms R134a or R404a spray can effectively reduce the temperature of the epidermis. R404a exhibited a stronger cooling effect than R134a. Cold air cooling at -10 °C for 10 s could effectively decrease the skin temperature, and deeper cooling could be achieved by cold air cooling compared with cryogen spray cooling.

Hydrothermal synthesis and characterization of rare-earth ruthenate pyrochlore compounds R_2Ru_2O_7(R=Pr_(3+),Sm(3+)-Ho(3+))

A series of pyrochlore oxides, R2Ru2O7 (R=Pr3+, Sm3+–Ho3+) were synthesized under mild hydrothermal conditions. All the samples crystallize in uniform octahedron characteristically. The products were characterized by powder X-ray diffraction, scanning electron microscopy, energy-disperse X-ray spectroscopy, and dc susceptibility, and the factors that affected the crystallization were discussed. It was found that the purity of products depends strongly on the raw materials and the amount of alkalinity in the initial reaction mixtures. The ZFC and FC susceptibilities of all of the compounds R2Ru2O7 at low temperature were also measured and discussed.