碳毡负载Sn气体扩散电极CO_2电化学还原性能

针对CO_2电化学还原中气体扩散电极可强化CO_2的传质,基于碳毡制备了负载锡-石墨烯催化层的新型气体扩散电极,研究了CO_2反应条件、电极厚度、催化剂载量及反应电位对CO_2电化学还原性能的影响。实验结果表明:与溶解态CO_2反应条件相比,采用气相CO_2反应条件电化学还原性能更好;一定范围内增加电极厚度和催化剂载量可以增加气-液-固三相反应界面,提升CO_2电化学还原性能;随着电解电位负移,甲酸产量增加,电流效率先增大后减小;实验中使用厚度为5 mm、载量为5 mg·cm-2的电极,在-1.8V(vs Ag/AgCl)条件下进行电化学还原时,平均电流密度为(12.79±1.27)mA·cm-2,甲酸电流效率达到最佳为41.55%±2.50%。     

电沉积制备多孔铅电极及其对CO2的电还原性能

采用铜片为基底,利用其自身析出的氢气泡为模板,通过电沉积的方法合成了具有三维多孔结构的铅沉积层,并将其作为电极材料应用到CO2的电还原反应中.考察了不同沉积时间及不同沉积电流密度对电极形貌及电催化还原CO2性能的影响,得出在5℃下,沉积电流密度为-6 A/cm2,沉积时间为20 s时,电极催化效果最好,在施加电位为-1.7V时生成甲酸的最高电流效率可达96.8％.     

Cu修饰的多孔碳材料高效电化学还原CO2为CO

将二氧化碳电化学还原为一氧化碳是一种实现碳循环和利用的有效途径。为了利用大量过剩的二氧化碳资源,本文制备了一种简单合成的电催化剂,以生物质壳聚糖为前体制备了含氮多孔碳基底,嵌入均匀分布的非贵金属铜纳米颗粒进行修饰,通过调节铜的负载量,达到充分利用铜金属的活性,从而在电化学二氧化碳还原过程中实现了优异的一氧化碳法拉第效率和选择性。在-0.6V vs. RHE时下,一氧化碳的最大法拉第效率（FE）为78%,并且没有其他有效产物的生成,从而一氧化碳的选择性达到了100%,电流密度为1.9mA/cm²。并且在0.1mol/L KHCO₃水溶液中连续电解13h以上,一氧化碳的法拉第效率和选择性基本保持不变,制备的电极材料具有优异的稳定性。     

定电位电解型电化学气体传感器稳定性研究

分析了影响定电位电解型电化学传感器长期稳定性的因素。以电化学一氧化碳传感器为例,重点介绍了催化剂粒度及均匀性、电极制备方法、电解液浓度等对传感器长期稳定性的影响。     

水溶液中电化学还原CO2的研究进展

CO₂作为一种潜在的碳资源,寻找一种有效的方法转移利用CO₂一直是社会关注的焦点。水溶液中电化学方法转化固定CO₂可在室温和常压下进行,通过选择不同电极和电极电势来改变产物、调控反应速率和选择性,因而具有潜在的优势。本文综述了水溶液中电化学还原CO₂的发展现状,介绍了水溶液中电还原CO₂的基本原理和电极上发生的主要反应;总结了水溶液中金属电极、气体扩散电极(GDEs)和复合电极等不同电极材料对CO₂还原产物的种类、选择性以及电流效率的影响;讨论了温度、CO₂分压等还原反应条件对反应速率和电流效率的影响。展望了水溶液中电还原CO₂技术的发展前景,认为利用水基溶液中丰富的[H],增强CO₂还原产物的燃料化程度,将在环境保护、资源利用和经济效益方面具有极大价值,符合绿色化学发展理念。     

CO2在氢氧化铯／甲醇溶液中铜电极上高效电化学还原成乙烯的研究

探讨了在氢氧化铯／甲醇电解液中,CO2在铜电极上的电化学还原。从CO2还原而得的主要产物有：甲烷、乙烯、乙烷、一氧化碳和甲酸。在－3．5V的还原电位（参比电极为银＋氯化银电极,饱和KCI溶液为缓冲溶液）下,生成乙烯的最大电流效率为32．3％。在－4．0V时,甲烷的最大生成效率为8．3％。乙烯与甲烷的电流效率比为（2．9－7．9）：1。在氢氧经铯／甲醇溶液中,与CO2还原反应相竞争生成氢气的反应的电流效率可抑制在23％以下。     

铋/纳米洋葱碳电极的制备及其电化学还原CO2性能研究

采用水热法制备Bi/MCNOs电极催化剂,通过XRD、SEM对Bi/MCNOs催化剂进行表征,考察了Bi/MCNOs电极电化学还原CO₂制甲酸的性能。结果表明,在水热过程中,MCNOs成功负载到Bi上,Bi/MCNOs具有更小的球状结构。Bi/MCNOs电极电化学活性表面积为Bi电极的3.4倍。Bi/MCNOs电极的电流密度是Bi电极的4倍,且具有更正的起峰电位。通过对KHCO₃电解液浓度、还原电位对电化学还原CO₂制甲酸的分析可知,KHCO₃电解液浓度为0.5 mol/L、电势为-1.6 V vs.Ag/AgCl时,电化学还原CO₂效果最好,具有较高的电流效率。由此可见,Bi/MCNOs电极具有更高的活性,可有效提高电化学还原CO₂的催化效果。     

石墨烯负载碳量子点复合材料的氧还原性能研究

通过高温热处理方法制备碳量子点(CQDs)/石墨烯(G)复合材料。采用TEM、HRTEM、Raman、EDX等手段对材料进行形貌和结构表征。运用循环伏安法(CV)、线性扫描伏安法(LSV)技术考察材料在碱性介质中的氧还原(ORR)电催化性能。结果表明,相对于单独的石墨烯(G-900)和单独的碳量子点CQDs-900,碳量子点(CQDs)/石墨烯(G)复合材料具有较好的氧还原性能,可能原因是复合材料的表面缺陷增强,活性位点增加。     

Pt/WC催化剂的制备及其在气体扩散电极上的氧还原性能

以喷雾干燥处理的偏钨酸铵为前驱体,采用CO/CO₂为还原碳化气氛,利用程序升温气固反应法制备了分散性良好的空心球状WC粉体,并分别以WC和Vulcan XC-72R碳粉为载体,采用液相沉积还原法制备了Pt/WC及Pt/C催化剂。XRD和SEM测试结果表明, 所制备催化剂中Pt/WC的Pt粒子粒径要大于Pt/C。酸性条件下氧电极极化曲线测试结果表明, Pt/WC的氧还原催化性能要优于Pt/C,这主要表现在同一电位下较高的电流密度及还原起始电位正移约28 mV。讨论了Pt/WC催化性能提高的可能原因及催化机理,并对控制条件下Pt/WC氧气扩散电极的交流阻抗谱进行了研究。     

结构化铜基催化剂电化学还原CO2为多碳产物研究进展

近年来,随着有关铜基催化剂价态、晶面、微观形态等结构化因素对其催化性能影响的研究不断深入,铜基催化剂电化学还原CO₂高选择性制备高附加值多碳（C₂₊）产物取得长足进展。本文系统综述了近五年来结构化铜基催化剂电化学还原CO₂生成C₂₊产物的研究报道,并分析总结了铜基催化剂表面混合价态、高活性晶面和丰富晶界的存在,以及富含限域空间的形态学结构（纳米线阵列、纳米树突和纳米多孔结构等）的构建与其电化学还原CO₂生成C₂₊产物的活性和选择性之间的构效关系。进一步提出了CO₂电化学还原领域发展的新趋势,即充分发挥各个结构化因素的协同作用,原位制备具有混合价态和丰富晶界的纳米多孔结构铜基催化剂,并在流通池中高效还原CO₂持续生成C₂₊产物。     

Electrochemical reduction of dilute chromate solutions on carbon felt electrodes

Carbon felt is a potential material for electrochemical reduction of chromates. Very dilute solutions may be efficiently treated due to its large specific surface area and high porosity. In this work, the up-scaling of this technology is investigated using a new type of separated cell and once-through flow of industrial rinse water. A significant enhancement of the process is obtained due to copper deposition during long-term operation. The co-deposition and re-solution of copper occurs depending on the inlet chromate concentration. When previously deposited copper is present a current-free reduction of chromate takes place resulting in current efficiencies apparently above 100%. Very high space time yields are obtained even for effluents at low concentration and optimised conditions (high flow rates and pH 2). The economic feasibility of the technology is also considered. Continuous, single-pass operation results in lower energy requirements than batch processing. The economic potential of the process is also evaluated in comparison with chemical detoxification of chromate. The operating costs for the electrochemical treatment of very dilute effluents on a carbon felt electrode are 30% lower than for the chemical method.     

Chromium removal using a porous carbon felt cathode

Removal of hexavalent chromium by an electrochemical process using a carbon felt electrode in a flow-through electrochemical cell was studied. Optimum operating conditions, such as pH and current density were investigated. It was found that at pH 3.5, current density 400 A m^–2 and flow velocity of 1.11 cm s^–1, the total chromium and Cr(VI) concentrations can be reduced to less than 5 mg l^–1 within 230 min operation for 5 l of solution with an initial concentration of 50 mg l^–1. It was found that the solution pH is a critical factor for the chromium removal process. To achieve high chromium removal efficiency, pH and current density must be carefully controlled.     

925银电极上同步电化学还原NO2-与CO2合成尿素

引言煤炭、石油等化石燃料燃烧的同时会产生大量氮氧化物(NOx)和二氧化碳(CO2),导致地球的生态系统遭受严重破坏[1]。NOx是导致酸雨、光化学烟雾的主要污染物,而CO2是主要的温室气体。目前国内外使用比较广泛的NOx废气处理方法可分为干法和湿法两大类,其中干法可以分为选择性催     

电催化还原二氧化碳制一氧化碳催化剂研究进展

电催化还原CO₂作为缓解能源危机和全球变暖的有效途径已成为催化领域的研究热点。然而,不同反应途径的氧化还原电位较为接近,使产物的选择性成为电催化还原CO₂所需解决的主要问题。迄今为止,在水性电解质中可实现CO₂选择性地转化为一氧化碳（CO）和甲酸（HCOOH）。本文简述了电催化还原CO₂制CO的机理,包括CO₂吸附过程、二电子转移过程和CO脱附过程。从贵金属的晶面设计、形貌调控和表面功能化对反应活性和产物选择性的影响,铁卟啉、钴酞菁和镍三嗪在还原CO₂为CO反应中的电子转移途径,非金属碳基材料中杂原子和碳基质间的耦合效应等方面,重点介绍了近年来贵金属催化剂、过渡金属络合物催化剂和非金属碳基材料催化剂的研究进展,总结了各类催化剂的优缺点。指出在三类电催化还原CO₂制CO的催化剂中,非金属碳材料具有较高的CO法拉第效率,尤其是非金属碳材料成本较低、制备简单、结构易调控,在电催化还原中具有潜在的应用优势,是有望实现商业化应用的新型催化剂的候选材料之一。     

Preparation of a Pb loaded gas diffusion electrode and its application to CO2 electroreduction

A Pb loaded gas diffusion electrode was fabricated and used for the electroreduction of CO₂ to formic acid. The Pb/C catalyst was prepared by isometric impregnation. The crystal structure and morphology of the Pb/C catalyst were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The preparation conditions of the gas diffusion electrode were optimized by adjusting the amounts of polytetrafluoroethylene (PTFE) in the gas diffusion layer and acetylene black in the catalytic layer. The electrochemical performance of the as-prepared gas diffusion electrode was studied by chronoamperometry and cyclic voltammetry. The optimized gas diffusion electrode showed good catalytic performance for the electroreduction of CO₂. The current efficiency of formic acid after 1 h of operation reached a maximum of 22% at -2.0 V versus saturated calomel electrode (SCE).     

Continuous electroreduction of CO2 to formate using Sn gas diffusion electrodes

Electrochemical valorization may be a strategy for mitigating climate change, as the process allows for CO₂ to be converted into industrially useful chemicals. The aim of this work is to study the influence of key variables on the performance of an experimental system for continuous electroreduction of CO₂ to formate with a gas diffusion electrode (GDE) loaded with Sn. A 2³ factorial design of experiments at different levels of current density (j), electrolyte flow rate/electrode area ratio (Q/A ratio) and GDE Sn load was followed. Higher rates and concentrations (i.e., 1.4·10^?3 mol m^?2 s^?1 and 1348 mg L^?1 with efficiencies of approximately 70%) were obtained with GDEs than with plate electrodes. The statistical design of experiments demonstrated that the Sn load had the most significant effect on rate and efficiency. However, despite these promising results, further research is required to optimize the process. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3557–3564, 2014     

烟气脱硫活性炭纤维毡催化剂的研究

将活性炭纤维毡用浸渍法进行处理,实验确定的浸渍条件为：浸渍混合液中含NH₄VO₃ 质量分数为197%, CsNO₃质量分数为068%,浸渍液温度70 ℃,1 250 mL浸渍液浸渍活性炭纤维（ACF） 20 g,每次浸渍时间6 h,重复浸渍3次。随后在N₂保护下于250 ℃焙烧50 min,冷却至室温得到ACF催化剂。在实验室模拟试验装置上对ACF催化剂的烟气脱硫反应特性进行测试。实验结果表明,对烟气脱硫的反应活性次序为：KI-ACF＞V₂O₅-Cs₂O-ACF＞空白-ACF。并且在烟气中含 SO₂0.225 mol·m^－3,空速为2 400 h^－1,反应温度348 K,测取实验数据,回归得到烟气在V₂O₅-Cs₂O-ACF上脱除硫的反应动力学方程:dc_SO2/dt=0.072exp(－7.843×10³/RT)c_SO2^1.025·c_O2^0.579。     

Electrochemical reduction of carbon dioxide at ruthenium dioxide deposited on boron-doped diamond

Study of carbon dioxide reduction at RuO₂-coated diamond electrodes showed that conductive metallic oxides are promising electrocatalysts for this process and allow higher reduction products to be obtained. The main reduction products obtained in acidic and neutral media were formic acid and methanol, with product efficiencies as high as 40 and 7.7%, respectively. It was observed that conductive diamond is a very well suited material for studying the electrocatalytic properties of conductive metallic oxides, because its use resulted in a negligible substrate effect. This feature will greatly enhance the ability to understand the relationships between the intrinsic electrochemical behavior and the electrocatalytic behavior, in view of developing new effective electrocatalysts. The use of conductive diamond could also allow better utilization of the electrocatalyst by avoiding the need for thick films.     

Pulse-mode electrochemical reduction of carbon dioxide using copper and copper oxide electrodes for selective ethylene formation

Although the electrochemical reduction of CO₂ at a copper electrode produces hydrocarbons, the activity for the conversion of CO₂ is significantly reduced after several tens of minutes by the deposition of poisoning species on the electrode. In order to solve the poisoning species problem, the electrochemical reduction of CO₂ was carried out using a copper electrode in the pulse electrolysis mode by anodic as well as cathodic polarization. The anodic polarization intervals suppressed the deposition of the poisoning species on the electrode, and the amount of two hydrocarbons produced, CH₄ and C₂H₆, decreased only slightly even after one hour. By choosing the appropriate anodic potential and time duration the selectivity for C₂H₆ formation was significantly enhanced. The enhancement was found to be due to the copper oxide formed on the copper electrode. The selectivity was further improved when the electrochemical reduction was carried out using a copper oxide electrode. The highest efficiency of about 28% was obtained at −3.15 V.     

聚吡咯改性石墨毡电极的氧还原性能及应用

通过电化学氧化聚合法对石墨毡(GF)进行了聚吡咯(PPy)改性,并利用SEM、FTIR、XPS、LSV和EIS对聚吡咯改性石墨毡电极的形貌结构、元素组成和电化学性质进行了研究,采用H_2O_2生成速率表征了改性电极的两电子氧还原活性。考察了支持电解质种类和聚合时间对改性电极结构和氧还原性能的影响。结果表明,通过改性能够在石墨毡表面引入吡咯氮结构,在恒–0.45 V阴极电势的条件下,以硫酸钠为支持电解质制得改性电极的两电子氧还原活性最高,H_2O_2生成速率为24.82 mg/(L·cm~2·h)。改性石墨毡的两电子氧还原活性随着聚合时间的延长先增加后降低,聚合时间为1000 s时所得改性石墨毡的两电子氧还原活性最高,H_2O_2生成速率达到29.40 mg/(L·cm~2·h)。以PPy/GF-Na_2SO_4-1000为阴极材料构建电芬顿体系降解来自乙基纤维素生产过程的高盐有机废水,阴极电势为–0.55V时,8h后废水的化学需氧量(COD)可降至100mg/L以下,去除率达到88.8%。PPy/GF-Na_2SO_4-1000经过5次循环实验后活性无明显变化。