2D/2D WO3/Ag:ZnIn2S4 Z型异质结复合物的构筑及可见光催化性能

构筑Z型异质结复合物是光催化领域解决电子-空穴对复合较快的常用方法,其独特的双光子体系能高效的提升光催化速率而备受关注。本文通过水热法原位构筑二维/二维(2D/2D)WO₃/Ag:ZnIn₂S₄ Z型异质结复合物,并且利用透射电子显微镜(TEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、紫外-可见漫反射光谱(UV-Vis DRS)、光电化学(PEC)和荧光光谱(PL)对其微观形貌、物相结构、元素化学态和光电性能等进行表征分析,以及采用可见光(加λ>420 nm的滤光片)照射来评价2D/2D WO₃/Ag:ZnIn₂S₄ Z型异质结复合物光解水制氢气和光降解甲基橙(MO)的催化性能。结果表明,在2D/2D WO₃/Ag:ZnIn₂S₄ Z型异质结复合物中,随着Ag:ZnIn₂S₄的含量增加,光催化性能也显著增强。当Ag:ZnIn₂S₄的质量分数为35.0%时,复合物表现出最佳的制氢速率(158.93 μmol.g_-1^.h_-1⁾与降解速率(0.18 min_-1^),这为基于WO₃纳米片设计和构筑2D/2D Z型异质结复合物用于可见光催化制氢和污染物降解提供了新的见解。     

双模板法CeO2/g-C3N4形貌结构特征及湿式催化性能

利用微波辅助双模板法、软模板法制备了一系列的CeO₂/g-C₃N₄复合催化材料,通过XRD、N₂吸附-脱附、XPS、SEM和TEM等方式对材料进行表征,并对其湿式催化性能进行研究。结果表明,双模板法制备的D-CeO₂/g-C₃N₄复合材料表现出立方相CeO₂和层叠g-C₃N₄的特征,比表面积和孔径较大,属于介孔结构,表面存在Ce^₃₊和Ce^₄₊,有利于氧空位的形成。加入1 g嵌段共聚物 F127,使用无水乙醇溶液为溶剂,调节混合液呈碱性,微波辐射反应120 min后得到的D-CeO₂/g-C₃N₄(7.5)样品,结构完整均匀,具有最佳形貌特征。控制反应温度75 ℃,D-CeO₂/g-C₃N₄(7.5)投加0.7 g,H₂O₂投加 0.5 mL,初始pH值为5时,100 mg/L的苯酚溶液COD去除率可达80%以上。 D-CeO₂/g-C₃N₄(7.5) 复合催化材料使用五次以后仍可达60%以上的催化降解效果。     

Z型g-C3N4/WO3·H2O的制备及其光催化CO2还原性能

以石墨相氮化碳(g-C₃N₄)和二水合钨酸钠为原料,采用水热合成法制备了复合材料g-C₃N₄/WO₃·H₂O(CNW-1),通过XRD、XPS、SEM、TEM对其进行了表征,探究了298 K、0.1 MPa条件下其对CO₂的可见光催化还原性能,并提出了可能的反应机理。通过调控WO₃结晶水含量可以实现CO和CH₄的产率调节,在反应10 h后,CNW-1具有最高的CH₄产率(0.33μmol/g),而g-C₃N₄/WO₃(CNW)具有最高的CO产率(0.67μmol/g)。该研究为CO₂选择性还原为C1化合物提供了一种有效策略,同时突出了以g-C₃N₄作为半导体构建Z型光催化体系在催化领域的应用潜力。     

热驱动CO2多相催化合成化学品研究进展

由于CO₂分子较高的化学惰性,导致其选择性活化及可控转化极具挑战。相比于电和光驱动CO₂催化转化,热驱动CO₂多相催化转化反应是操作简便、目标产物可调且产品收率较高的方法。通过该类反应实现CO₂还原或非还原制备多种化学品既可促进CO₂的资源化利用,又可有效缓解温室效应,在环保、能源和材料等领域具有重要意义。本综述基于作者在CO₂捕集和转化方面的研究工作,结合近年来国内外的相关文献,对目前热驱动多相催化CO₂转化为CO、CH₄、甲酸、甲醇、碳氢化合物和其它精细化学品的研究现状进行综合评述。重点讨论反应机理、所用催化剂及反应体系的研究进展,并对其未来的研究方向进行了前景展望和探讨。     

ML-WO3/TiO2异质结的制备及其对罗丹明B的光催化降解

采用空间限域法制备了单层三氧化钨纳米片(ML-WO₃),然后将其与TiO₂复合得到ML-WO₃/TiO₂纳米材料,被用来在模拟太阳光下对罗丹明B进行光催化降解。ML-WO₃/TiO₂的组成和光学特性通过扫描电镜、透射电镜、高分辨透射电镜、X射线衍射、紫外-可见吸收光谱和光致发光光谱手段进行表征。结果证实,纳米ML-WO₃/TiO₂克服了纯TiO₂带隙较大的缺陷,在全波段太阳光表现出比ML-WO₃和TiO₂更强的吸收性能,ML-WO₃与TiO₂之间具有明显的协同效应。活性物种捕获实验表明.OH和.O_2^-自由基是RhB降解的主要活性物种。ML-WO₃和TiO₂之间构建的Z型异质结电荷转移路径能够保证光生载流子的高效分离和重组。在5次循环实验后ML-WO₃/TiO₂的光催化活性仍能接近80%,具有良好的光化学稳定性。通过高效液相色谱-质谱检测RhB的中间产物,推测了RhB可能的降解路径。     

Laboratory study of methane oxidation in paddy soils

Methane oxidation in paddy soils was investigated under laboratory conditions. Paddy soils collected before early rice transplanting could not oxidize atmospheric CH₄ but could oxidize CH₄ when the concentration exceeded 10 μl l^-1. Initial CH₄ oxidation rate increased with the increase of initial CH₄ concentration. Soil with the maximum potential to produce CH₄, also had the maximum CH₄ oxidation activity and the maximum emission flux from paddy soil. High CH₄ concentration stimulated the oxidation of CH₄. After 10 days' incubation under atmosphere containing 1000 μl^-1 or 10⁴ μl l^-1 CH₄, the soil which could not oxidize atmospheric CH₄ was able to oxidize it. This revised version was published online in August 2006 with corrections to the Cover Date.     

Characteristics of methane oxidation in a flooded rice soil profile

Laboratory experiments were conducted to study the variation of CH₄ oxidation patterns in flooded rice soil profiles. The results indicated that surface soil presented the strongest CH₄ oxidation activities as shown by the highest values of the two kinetic parameters of CH₄ oxidation, V_max and K_m in the ecosystem without rice plants. V_max and K_m decreased significantly from top to bottom in the paddy rice soil profile, ranging from 12.5 to 1.2 μg h^-1 g^-1 and 165 to 4.1 μg g^-1, respectively. In addition, we studied the effect of headspace N₂, O₂ and their ratio on CH₄ emission and oxidation to provide information on the sensitivity of methanogens and methanotrophs to soil redox change resulted from gas transportation through arenchyma. Methane emission rate increased, however, CH₄ oxidation rate decreased with a decrease of O₂ concentration in the headspace. Headspace H₂ increased CH₄ emission rate substantially. In addition to H₂ being a substrate for CH₄ formation, the change of soil redox potential to a considerably low level H₂ should also contribute to the increase in CH₄ emission. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nitrous oxide emission from a rice paddy field in Japan

The flux of nitrous oxide (N₂O) from a rice paddy field to the atmosphere was measured at Ryuhgasaki experiment station in Ibaraki Prefecture of Japan by closed chamber method, from the summer of 1992 to the summer of 1993. During the rice-cultivated and flooding periods when methane (CH₄) was emitted, no emission or uptake of N₂O was measured because the flux values were below the detection limits. After the final water drainage for harvest in August or September, N₂O began to emit from the soil surface while the emission of CH₄ was stopped, and N₂O was emitted continually until the re-flooding day in the following spring. In the first few months after the final water drainage, the N₂O flux was in the range of 10–20 μgN/m²/hour, then in the latter several months during the cold season, the N₂O flux was less than 10 μgN/m²/hour. The vertical profiles of N₂O, CO₂ and CH₄ concentrations in the plowed layer of the soil down to a depth of 20 cm, were also measured six times in the fallow season. The maximum concentrations of N₂O and CO₂ were found in the plowed layer in the early period, and which demonstrates that most of the N₂O was produced in the plowed layer through nitrification, due to the decomposition of organic matter accumulated in the plowed layer during the rice-growing and water-flooding period. On the contrary, the vertical profiles in the cold season showed a gradual increase in the concentrations of N₂O and CO₂ in the plowed layer. It clearly indicates that a small amount of N₂O was emitted to the atmosphere by diffusion through the plowed layer from the sub-soil layer where a large source of N₂O was expected to exist. This revised version was published online in August 2006 with corrections to the Cover Date.     

Preliminary studies on N2O emission fluxes from upland soils and paddy soils in China

In this paper, we presented the preliminary results of N₂O fluxes from Chinese upland and rice paddy fields. The mean N₂O flux from upland fields of North China is 30.6 μg N₂O-N m^-2 h^-1; the average N₂O flux from Chinese rice paddy field is 39.5 μg N₂O-N m^-2 h^-1. The effects of cropping system, water management and application of N fertilizer and organic manure on N₂O emission from rice paddy field have also been presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

Methane oxidation in soils with different textures and land use

Intact core samples from soils with different textures and land use were tested for their capacity to oxidise methane. The soil cores were taken from arable land, grassland and forest. It was found that coarse textured soils (6.74–16.38 μg CH₄ m^-2 h^-1) showed a higher methane uptake rate than fine textured soils (4.66–5.34 μg CH₄ m^-2 h^-1). Increasing soil tortuosity was thought to reduce the methane oxidation rate in fine textured soils. The oxidation rate of forest soils (16.32–16.38 μg CH₄ m^-2 h^-1), even with a pH below 4.5, was very pronounced and higher than arable land (11.40–14.47 μg CH₄ m^-2 h^-1) and grassland (6.74–9.30 μg CH₄ m^-2 h^-1). Within the same textural class arable land showed a faster methane uptake rate than grassland. In grassland with a fine texture, even methane production was observed. Nitrogen availability and turnover in these land use systems were thought to cause the different oxidation rates. Decreasing the moisture content slowed down the oxidation rate in all soils. This could be caused by an increased N turnover and a starvation of the methanotrophic bacteria. This revised version was published online in August 2006 with corrections to the Cover Date.     

单分散Gd2O3:Eu3+@SiO2的合成及性能

采用溶胶-凝胶法合成SiO₂包覆Gd₂O₃:Eu³⁺球型核壳粒子,并对所得产物进行XRD,FT-IR,SEM,TEM,XDS,PL等测试。XRD结果显示:壳层Gd₂O₃:Eu³⁺在600℃开始结晶,随着煅烧温度的升高结晶性提高。SEM,TEM测试结果显示所得核壳粒子具有高分散、均匀球型形貌、粒径大小300nm左右。在255nm的紫外光激发下,合成的荧光粉具有很强的610nm的特征红光。     

致密油藏CO2驱响应性防窜体系的制备及性能

以3-二甲胺基丙胺和油酸为主剂制备具有叔胺结构的CO₂响应性单体N,N-二甲基油酸酰胺丙基叔胺(DOAPA),将其与有机反离子互配构建具有CO₂响应性的蠕虫状胶束(CO₂-TWMS)。通过体系与CO₂接触前后的电导率、化学结构和微观形貌变化表征体系的响应性,结合体系表面活性变化及致密基质/裂缝双重介质CO₂驱替与CO₂-TWMS防窜过程中的压力和采收率变化揭示CO₂-TWMS防窜性能与机制。实验结果表明,当反离子为对甲苯磺酸钠,与DOAPA的摩尔比为1:1时,CO₂-TWMS体系的黏度最大。CO₂和N₂能够刺激体系电导率在0.9ms/cm和1.95ms/cm之间可逆变化、诱导微观形貌在蠕虫状胶束和球形胶束间转换。此外,CO₂能够将体系临界胶束浓度从1mmol/L降低至0.25mmol/L,最低表面张力从30.2mN/m降低至29.1mN/m,体系在气液界面的吸附效率和效能增强,有利于胶束的形成。在致密基质-裂缝双重介质中,CO₂诱导蠕虫状胶束形成,增大驱替过程中的压差,扩大CO₂驱替波及效率,采收率提高22.6%。     

PVAm/PAN复合膜的制备及其对CO2/CH4的分离性能

New polymeric membrane materials——polyvinyl amine (PVAm) with different primary amine contents were synthesized.By covering polyacrylonitrile(PAN) ultrafiltration membranes with PVAm, the PVAm/PAN composite membranes for CO₂/CH₄ separation were prepared. The composite membranes containing more primary amino groups have higher selectivity for CO₂/CH₄.The cross-linking of acid or glutaradehyde could improve the gas permselectivity of the composite membranes. With decreasing CO₂ content in the feed gas, the CO₂/CH₄ separation factor increased.When the feed gas was 25%(vol) CO₂ and 75%(vol) CH₄, the CO₂ permeation rate was 4.1×10^-9cm³(STP) •cm^-2•Pa^-1•s^-1, and the CO₂/CH₄ separation factor was 180.     

CuBi2O4/BiOBr@GH双功能光催化剂的制备及其光催化性能

采用溶剂热法制备Z型CuBi₂O₄/Bi OBr(CBOB)异质结，并与石墨烯水凝胶(GH)复合得到CuBi₂O₄/BiOBr@GH(CBOBG)。通过X射线衍射、X射线光电子能谱、扫描电子显微镜、透射电子显微镜、N₂吸附-脱附、紫外-可见光谱、荧光光谱和电化学等表征方法对催化剂的晶体结构、表面组成、微观形貌、比表面积与光电性能进行分析。在可见光下，通过降解四环素耦合还原Cr(Ⅵ)实验，考察了CBOBG的光催化活性。实验结果表明，CBOBG在120min内，对四环素的降解率达到了86.1%，对Cr(Ⅵ)的还原率达到了100%。通过活性物种捕获实验证明，降解过程的主要活性物质为超氧自由基和光生空穴，还原过程的主要活性物质为光生电子。     

Nd2O3掺杂对MnCoNi系NTC热敏电阻电性能的影响

采用传统固相法制备了Co_0.7-xMn_2.1Ni_0.2Nd_xO₄(X=0,0.04,0.06,0.08)样品。利用X射线衍射、SEM、阻值测量等手段,研究了微量Nd₂O₃掺杂对MnCoNi系NTC热敏电阻材料的影响。研究结果表明：在0≤X≤0.08掺杂范围内,随着Nd₂O₃掺杂量的增加,MnCoNi系NTC热敏电阻的晶相结构和阻温特性并没有改变,晶粒变小,电阻率和B值分别由202.8Ω.cm、3432K,上升到2944.7Ω.cm、4152K;老化特性得到显著提高,△R₂₅/ R₂₅和△B_25/50/ B_25/50变化率分别由1.15%,0.75%降至0.31%,0.22%。     

g-C3N4/BiVO4异质结的制备及其在环境治理中的应用

通过负载法成功制备了g-C₃N₄/BiVO₄异质结,采用XRD、SEM、BET、UV-Vis DRS、Mott Schottky、SPV等技术对样品的结构与性质进行分析,以光催化降解RhB和光催化还原CO₂评价其光催化活性。结果表明,g-C₃N₄和BiVO₄能带结构匹配,能够组成“Z”型异质结,并有效提高光生载流子的分离效率,同时保留g-C₃N₄导带电子较强的还原性和BiVO₄价带空穴较强的氧化性,最终提高光催化活性,其中当g-C₃N₄的负载量为3%时,样品展现了最佳的光催化活性,在光催化降解RhB实验中,经过180min光照后,降解率达到95.3%,反应速率常数达到0.0166min^-1;而在光催化还原CO₂的实验中,经过4h光照后,CO和O₂的产量达到70....     

Ni/γ-Al2O3催化苯乙烯-异戊二烯-苯乙烯嵌段共聚物加氢研究

以硝酸镍、γ-Al₂O₃、碳酸铵为原料,采用沉积沉淀法制备 Ni/γ-Al₂O₃催化剂,并将其应用于苯乙烯-异戊二烯-苯乙烯嵌段共聚物(SIS)催化加氢。通过XRD、TEM、XPS、₁^HNMR和DSC对催化剂和产物进行了表征。从载体类型、负载量、反应条件以及循环次数等方面对SIS加氢性能进行考察,结果表明：以环己烷为溶剂,反应温度为140 ℃,反应压力为1 MPa的条件下,催化剂展现出最优活性。聚异戊二烯的嵌段加氢度达到85%,副反应苯环的加氢度小于10%。     

碳纳米管改性铁酸铋光催化还原CO_2合成甲醇

以溶胶-凝胶法制备了BiFeO3和BiFeO3/单壁碳纳米管(single-walled carbon nanotubes,SWCNTs)复合粉末。并分别用X射线衍射、紫外和可见光谱及气相色谱分析表征了催化剂的结构、可见光响应性能及催化活性,讨论了碳纳米管改性对催化剂可见光响应性及光催化活性的影响。结果表明:BiFeO3和BiFeO3/SWCNTs均具有较好的可见光响应性及催化活性,碳纳米管的加入不仅可以明显强化铁酸铋的紫外及可见光响应性能,同时可以使BiFeO3光催化还原CO2合成甲醇的性能增加1倍,单位质量BiFeO3/SWCNTs光催化还原CO2合成甲醇的累积产率最高可以在4～6h达到1000μmol/g。     

NiPd/TiO2催化剂的制备及其催化甲酸分解制氢性能

高效、清洁且无毒无害的催化剂是实现以甲酸(HCOOH)为化学储氢材料分解制氢的重点。本文采用水热法在453K的条件下制备TiO₂载体,再通过浸渍法向其中加入总量为0.1 mmol的NiCl₂.6H₂O和K₂PdCl₄金属溶液,将活性组分Ni、Pd负载到TiO₂载体上合成NiPd/TiO₂催化剂,并探究其对催化甲酸分解制氢的性能的影响。探究结果表明,在光照条件下,NiPd/TiO₂催化剂中,当金属Ni:Pd比例为2:8时,催化剂的反应转化频率(TOF)值最大,此时催化剂的 TOF 为3528 h_-1^,且该催化剂上甲酸分解的活化能(E_a)为53.9 kJ/mol。关键词：镍钯催化剂;甲酸;分解制氢;二氧化钛;光照中图分类号：TQ630 文献标识码： A 文章编号：     

Ni/SiO2催化剂的2-MF加氢性能研究

本研究以硝酸镍为镍源,酸/碱性硅溶胶为硅源,采用共沉淀法制备了Ni/SiO₂催化剂。采用固定床反应器,评价Ni/SiO₂催化剂对于2-甲基呋喃(2-MF)气相加氢合成2-甲基四氢呋喃(2-MTHF)的反应性能。通过XRD、N₂等温吸附-脱附、H₂-TPR、NH₃-TPD、XPS、FT-IR和TEM等方法对催化剂结构进行表征,研究硅溶胶的酸碱性对Ni/SiO₂催化剂结构及性能的影响。结果表明：以酸性硅溶胶为硅源制备的Ni/SiO₂催化剂弱酸中心酸量多并且存在中强酸性中心,比表面积高,平均孔径大,因而该催化剂活性和2-MTHF的选择性高。Ni/SiO₂催化剂稳定性良好,在90 ℃,2 MPa,WHSV=4.4 h_?¹条件下连续反应200 h,2-MTHF的收率均保持在95.7%。关键词：2-甲基四氢呋喃;2-甲基呋喃;共沉淀法;Ni/SiO₂;酸碱性