反应条件对铜催化CO2电还原的影响

工业规模的化石能源消耗导致大气中二氧化碳含量不断增加,CO₂转化利用成为人们日益关注的热点问题. 金属铜因其成本低廉、储量丰富,并且具有独特的CO₂亲和力能够生成多碳化合物,是目前CO₂电还原中研究最为广泛深入的电极材料. 由于阴、阳离子的特征吸附对Cu电极性能有显著影响,并且不同反应体系中对Cu电极上CO₂吸附、活化影响也有所不同,因此导致金属Cu电极上报道的电催化活性、产物种类与选择性等都非常宽泛. 基于此,有必要系统地研究各种反应条件对金属Cu电极电催化CO₂还原性能的影响. 作者选择了平均粒径为600 nm的商品化金属Cu颗粒作为电还原CO₂的催化剂,研究了不同反应条件包括各种常用电解质溶液、KHCO₃的浓度以及H型电解池和流动池. 实验结果表明,浓度为0.5 mol·L ^-1的KHCO₃作为电解质溶液具有较好催化活性和较高的产物分电流密度,流动池可以进一步提高主要产物甲酸盐和CO的分电流密度. 本研究工作从反应条件的角度对CO₂还原的电催化转化进行了系统研究,有助于理解电解液和反应器等因素对CO₂电还原反应过程的影响规律.     

Co_3O_4纳米片的制备及对H_2O_2电还原反应的催化性能

通过恒电势电沉积和加热处理在泡沫镍基体上制备了Co3O4纳米片.利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)等手段对纳米片的形貌和结构进行了表征.采用线性伏安扫描和计时电流技术研究了Co3O4纳米片电极对H2O2的电还原性能.结果表明,在3.0 mol/L KOH和0.4 mol/L H2O2溶液中,当电压为-0.4 V(vs.Ag/AgCl)时,线性伏安扫描电流密度达到-0.386 A/cm2,在1000 s测试时间内,计时电流密度衰减很小,表明Co3O4纳米片电极对H2O2具有很高的活性和稳定性.     

NiCo2O4 纳米线对H2O2电还原的催化性能

以无模板生长法制备了泡沫镍载NiCo2O4纳米线正极材料, XRD和SEM表征结果表明, 所得材料为NiCo2O4纳米线, 以循环伏安法和计时电流法研究了泡沫镍载NiCo2O4纳米线对H2O2电还原的催化性能. 结果显示, 在0.4 mol/L H2O2 和 3.0 mol/L NaOH 溶液中, 当电压为-0.4 V(vs. Ag/AgCl)时, 循环伏安的电流密度达到125 mA/cm2; 当电压为-0.2, -0.3和 -0.4 V 时, 在30 min 的测试时间内, 计时电流密度几乎均为一常数, 表明以泡沫镍载NiCo2O4纳米线为催化剂电还原H2O2具有很高的活性和很好的稳定性.     

NiCo2O4对H2O2在碱性溶液中电化学还原反应的催化行为

利用溶胶-凝胶法合成纳米NiCo2O4,并利用X射线衍射和透射电镜分析其结构和表面形貌. 结果表明NiCo2O4具有尖晶石结构, 平均粒径约为15 nm. 利用电势线性扫描和恒电势法测定了其对H2O2在碱性溶液中电化学还原反应的催化性能. 发现NiCo2O4对H2O2电化学还原具有高的催化活性和稳定性, 在H2O2浓度低于0.6 mol·L-1时, 其电化学还原反应主要通过直接还原途径进行. 以NiCo2O4为阴极催化剂的Al-H2O2半燃料电池在室温下的开路电压达1.6 V; 在1.0 mol·L-1 H2O2溶液中, 峰值功率密度达209 mW·cm-2, 此时电流密度为220 mA·cm-2.     

CO2和N2电还原中缺陷及界面工程的最新进展

实现碳氮循环是人类社会发展的迫切要求,也是催化领域的热门研究课题。在可再生能源的推动下,电催化技术引起了人们的广泛关注,且可以通过改变反应电压获得不同的目标产品。基于此,电催化技术被认为是缓解当前能源危机和环境问题的有效策略,对实现碳中和具有重要意义。其中,电催化CO₂还原反应(CO₂RR)和N₂还原反应(N₂RR)是一种有前途的小分子转化策略。然而,CO₂和N₂均为线性分子,其中C＝O和N≡N键的高解离能导致了它们高的化学惰性。此外,最高占据分子轨道(HOMO)和最低未占分子轨道(LUMO)之间的巨大能量间隙使它们具有高的化学稳定性;且CO₂和N₂的低质子亲和力使它们难以被直接质子化。另一方面,由于CO₂RR和N₂RR与析氢反应(HER)具有相近的氧化还原电位,造成其与HER之间存在竞争性关系,这也是致使催化剂在CO₂RR和N₂RR转化效率低的重要影响因素。因此,CO₂RR和N₂RR仍然面临着过电位高及法拉第效率低等问题。为了克服这些瓶颈,人们为提升CO₂RR和N₂RR电催化剂性能做出了很多努力。众所周知,电催化过程发生在催化剂表面,主要涉及质量传递和电子转移等过程。由此可见,催化剂的性能与其质量和电子传输能力密切相关,而调控催化剂表面结构可以优化活性点的质量和电子转移行为。电催化剂的缺陷和界面工程可通过表面原子工程来实现电子结构调控,对于提高气体吸附能力、抑制HER、富集气体及稳定中间产物等具有重要意义。到目前为止,所报道的各种缺陷和复合电催化剂在提高CO₂RR和N₂RR催化性能等方面均表现出巨大的潜力。在此,我们综述了CO₂RR和N₂RR中催化剂缺陷工程及界面工程的最新进展;首先讨论了四种不同的缺陷(空位、高指数晶面、晶格应变和晶格无序)对CO₂RR和N₂RR性能的影响;然后,总结了界面工程在聚合物-无机复合材料催化剂中的重要作用,并给出了典型实例;最后,展望了原子级电催化剂工程的发展前景,提出了开发和设计高效CO₂RR和N₂RR电催化剂的未来发展方向。     

铜-镍合金电极表面组成及状态的变化对硝基苯电还原的影响

铜-镍合金电极表面组成及状态的变化对硝基苯电还原的影响;Monel合金电极;表面状态;硝基苯;对氨基苯酚;电还原     

SnO2/GDE阴极的制备及电催化还原CO2产甲酸性能

采用低温水热合成法制备了碳纸基底的SnO₂气体扩散电极(SnO₂/GDE), 并对其物化特性与催化还原CO₂产甲酸性能进行了研究. 扫描电子显微镜、 X射线衍射及X射线光电子能谱表征结果表明, 在60, 75, 100 ℃下制备的催化剂均为分散性良好的纳米SnO₂粉体, 其粒径分别为7.9, 11.8和12.9 nm. 循环伏安、 线性扫描伏安和电化学交流阻抗测试结果显示电极均具有优异的电催化活性, 其电化学活性表面积分别为150, 470, 240 cm ², 通过等效电路拟合后电阻分别为8.5, 3.9, 6.6 Ω·cm ². 在-1.8 V(vs. SCE)电位下电解, 通入电量500 C时, 电极都具有较高电催化还原CO₂产甲酸性能, 而75 ℃下制备的电极性能最佳, 产甲酸电流密度为22.8 mA/cm ² , 产甲酸法拉第效率高达93.5%; 该电极经过20 h长时间电解后, 产甲酸电流密度可维持在12.8 mA/cm ² , 产甲酸法拉第效率稳定在约65%.     

ZrO2在Rh/γ-Al2O3催化剂中对NO催化还原反应的作用

测定了含ZrO2的Rh/γ-Al2O3催化剂上NO+C2H4和NO+C2H4+O2的反应活性,并应用TPR、XRD、BET比表面等表征了ZrO2的加入方式和晶型对Rh/γ-Al2O3催化剂活性和结构的影响。结果表明,ZrO2的加入一定程度地抑制了Rh3+与γ-Al2O3之间的相互作用和γ-Al2O3的相变,提高了催化剂的热稳定性,明显提高了850℃老化样品的NO+C2H4反应活性。对于NO+C2H4+O2反应,含ZrO2样品的选择还原活性却较低,表明反应机理不同,而且ZrO2对C2H4的深度氧化有促进作用,但老化后活性下降幅度比不含ZrO2的样品小。     

RuO_2/TiO_2纳米薄膜的新构建及对CO_2的电催化还原

在旋涂有球状纳米TiO2薄膜的导电玻璃(ITO)基底上采用循环伏安法(CV)电沉积RuO2作为电催化还原CO2的阴极.采用场发射扫描电子显微镜(FE-SEM)表征了RuO2/TiO2纳米薄膜的形貌,并应用近稳态电位扫描法和计时电流法(i～t)研究了薄膜的电催化CO2性能.结果表明所构建的RuO2/TiO2薄膜中纳米粒子大小均匀、排列致密,且较传统热分解法所得催化剂有更好的电催化性能.     

Sol-gel transition of polyacrylonitrile/propylene carbonate solution

The thermoreversible gelation of polyacrylonitrile (PAN)/propylene carbonate (PC) solution was investigated by calorimetric, thermomechanical, optical, and rheological measurements. Two endothermic signals are observed for PAN/PC gels in DSC thermograms, and the peak temperature of the higher melting endotherm coincides with the gel melting temperature determined from the TMA thermogram. SEM micrographs show that the overall structure is separated into two phases and is composed of sperical domains, which may be formed upon passing through the thermodynamically unstable or metastable state via the liquid-liquid phase separation. The gelation rate increases with the aging temperature. This is also discussed on the basis of the elasticity theory of the fishnet gel. © 1994 John Wiley & Sons, Inc.     

Nucleation and growth mechanism for the electropolymerization of aniline in trifluoroacetic acid/lithium perchlorate/propylene carbonate medium

In the present work, the nucleation and growth mechanism for the electropolymerization of aniline in propylene carbonate medium containing 0.06 M trifluoroacetic acid and 0.05 M lithium perchlorate was investigated at different potentials on highly oriented pyrolytic graphite (HOPG) by potentiostatic current-time transients (i-t) and atomic force microscopic (AFM) measurements. The electrochemical data fitted with the theoretical curves for nucleation and growth suggest that the electropolymerization of aniline consists of progressive nucleation followed by 3D growth at an early stage and layer-by-layer growth in subsequent periods. The results obtained from transient analysis were in good agreement with the results of the AFM analysis. In our previous studies with aqueous solutions, we observed only progressive nucleation followed by a 3D growth mechanism for the electropolymerization of aniline in a higher potential range, 1.5–2.0 V vs. Ag/AgCl. Hence, the results obtained from the present work indicate that the nucleation and growth mechanism depends on the medium.     

聚碳酸丙烯酯中碳酸丙烯酯含量的测定

建立了气相色谱分析聚碳酸丙烯酯中碳酸丙烯酯含量的方法,该方法操作简单,准确度高,可满足工业检测需求.     

Vibrational spectroscopic studies on ion solvation of lithium perchlorate in propylene carbonate + N,N-dimethylformamide mixtures

The infrared (IR) and Raman spectra are reported for solutions of lithium perchlorate in propylene carbonate (PC), N,N-dimethylformamide (DMF) and PC + DMF mixtures. The band splittings of symmetric ring deformation for PC and O=CN deformation for DMF suggest that there is a strong interaction between lithium cations and solvent molecules. The solvent molecules have been assigned to two types, the free and complexed molecules. By a comparison of the intensity for the corresponding bands, it has been concluded that Li+ cations are preferentially solvated by DMF molecules in the LiClO4/PC-DMF solutions. This has been explained by the difference in values of donor number.     

Ion-molecule interactions in solutions of lithium perchlorate in propylene carbonate + diethyl carbonate mixtures: an IR and molecular orbital study

FTIR spectra have been recorded and analyzed for solutions of lithium perchlorate in propylene carbonate (PC), diethyl carbonate (DEC), and PC + DEC mixtures. It has been shown that the carbonyl stretch bands for PC and DEC are very sensitive to the interaction between Li+ and the solvent molecules. They split with addition of LiClO4, indicating a strong interaction of Li+ with PC and DEC through the oxygen group of PC and both oxygen and ether oxygen atoms of DEC. In conjunction with molecular orbital calculation, the optimized geometries of solvation are given. In addition, solvent separated ion pairs and contact ion pairs were observed in LiClO4/DEC solutions, and no preferential solvation of Li+ in LiClO4/PC + DEC solutions were detected.     

Nanostructured fluids based on propylene carbonate/water mixtures

The microstructure of aggregates formed by sodium dodecyl sulfate (SDS) and 1-pentanol in mixtures of water and a polar aprotic solvent (propylene carbonate, PC) was investigated by means of pulsed gradient spin-echo NMR, dynamic light scattering, viscosity, and conductivity measurements. PC partitions itself between micelles and aqueous bulk. The fraction of micellized propylene carbonate remains constant along PC-dilution, and the phase separation takes place when the composition of continuous phase attains the PC/water miscibility gap. The micellized PC is present mainly in the micelle's palisade and strongly increases the total interfacial area, thus acting as a cosurfactant. At high PC content, the system is composed by very small aggregates (around 10 A in radius) made by few SDS molecules (10-6) and PC and pentanol. The resulting system can be described as a nanostructured fluid with a huge interfacial area and a small dispersed phase.     

水溶性硅油对超临界CO_2介质中丙烯酸聚合反应的影响

：通过对水溶性硅油浓度的改变，研究其对超临界CO2介质中丙烯酸聚合反应的影响。研究表明水溶性硅油可起到分子量调节剂的作用。随着硅油的加入，产物分子量降低，但当硅油浓度过大时，由于硅油在超临界CO2中溶解度的限制，夹带单体聚沉在反应釜底部形成富单体相，分子量有所上升。此外，扫描电镜照片（SEM）显示不同浓度的水溶性硅油对聚丙烯酸分子形态的影响不同，硅油含量越大，聚丙烯酸分子粒径越小，分子量分布越均匀。     

The coordination state of CoCl2 in propylene carbonate

The formation of chlorocomplexes of cobalt(II) chloride in propylene carbonate (PC) solution has been investigated spectrophotometrically and conductometrically. The influence of the nature of the solvent on the coordination state of cobalt(II) chloride is discussed in terms of donor number (DN) and dielectric constant.

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Der Koordinationszustand von Kobalt(II)-chlorid in Propandiol-1,2-carbonat

Zusammenfassung Die Bildung von Chlorokomplexen des Kobalt(II)-chlorids in Propandiol-1,2-carbonat (PC) wird auf spektrophotometrischem und konduktometrischem Wege untersucht. Die Abhängigkeit des Koordinationsverhaltens von Kobalt(II)-chlorid von der Donorzahl (DZ) und der Dielektrizitätskonstante in verschiedenen Lösungsmitteln wird diskutiert.

     

Infrared (attenuated total reflection) study of propylene carbonate solutions containing lithium and sodium perchlorate

Attenuated total reflection infrared spectroscopy was used to examine the concentration dependent solvation of LiClO4 and NaClO4 electrolytes in propylene carbonate (PC). Factor analysis and curve fitting techniques were performed on the measured spectra and the results compared with ab initio computations to provide evidence for ion-solvent solution geometries. Factor analysis of the measured data allowed the identification of the spectrum of ion-associated PC that is uniquely different from the self-associated PC spectrum. The results indicate Li+ and ClO4- ions are contact ion-paired even at relatively low electrolyte concentrations whereas Na+ and ClO4- ions are not, up to approximately 2 mol dm-3.     

Potential-induced phase transition of low-index Au single crystal surfaces in propylene carbonate solution

In situ scanning tunneling microscopy (STM) was employed to examine the surface structures of Au(111), Au(100), and Au(110) single crystals in propylene carbonate (PC) containing tetrabutylammonium perchlorate (TBAP). All three electrodes exhibited potential-induced phase transition between the reconstructed and unreconstructed (1 × 1) structures at negative and positive potentials, respectively. The potential-induced phase transition of the Au electrode surfaces is attributed to the interaction of the TBA cation and the perchlorate anion at the electrode surface, which is similar to that which takes place in aqueous solutions. In addition to static atomic structures, dynamic processes of both the reconstruction and the lifting of the reconstruction were investigated by means of in situ STM. The lifting of reconstructed Au(111)-(√3 × 22) on Au(111) to the (1 × 1) structure is completed within 1 min at a positive potential. The diffusion of Au atoms on the Au(100) plane in the PC solution proceeds more rapidly than that in the aqueous solution, suggesting that the PC solvent plays an important role in accelerating the diffusion of Au atoms.