电催化二氧化碳还原反应(CO_(2)RR)可以将二氧化碳转化为具有高经济价值的碳氢化合物,被认为是实现碳中和并缓解能源危机的一种有潜力的技术.铜(Cu)作为一种最有应用前景的非贵金属催化剂之一,表现出较高的催化CO_(2)RR转化为多碳产物(C...电催化二氧化碳还原反应(CO_(2)RR)可以将二氧化碳转化为具有高经济价值的碳氢化合物,被认为是实现碳中和并缓解能源危机的一种有潜力的技术.铜(Cu)作为一种最有应用前景的非贵金属催化剂之一,表现出较高的催化CO_(2)RR转化为多碳产物(C_(2+))的活性.然而,电催化CO_(2)还原成C_(2+)产物涉及一个动力学过程缓慢的C-C偶联反应,这导致C_(2+)产物的选择性较低,电流密度低,阻碍了其在工业电解槽中的实际应用.同时,CO_(2)RR产物的选择性不仅取决于热力学速率决定步骤,还取决于传质控制动力学.CO_(2)RR发生在固-气-液三相反应界面,气-液的平衡扩散可以有效抑制析氢竞争反应,进而提高CO_(2)RR的反应效率.本文设计合成了一种富晶界的Cu纳米带催化剂,并构建了气-液平衡扩散的电极结构,用于高效电催化二氧化碳还原制备乙烯(C_(2)H_(4)).以一种碱式碳酸铜(Cu_(2)CO_(3)(OH)_(2))纳米带为前驱体,在原位电化学还原条件下,前驱体中的Cu2+离子获得电子被还原为金属Cu,而释放的CO_(3)2-和OH-混合阴离子调节金属Cu的生长.生成的Cu纳米带由细小的纳米颗粒堆积而成,并暴露出大量的由Cu(111),Cu(200)和Cu(220)晶面形成的富晶界结构(GBs).同时,在CO_(2)RR测试中发现催化剂层的厚度是影响CO_(2)和电解质传质的关键因素.通过调整催化层厚度,CO_(2)和电解质可以同时到达催化剂表面,参与到CO_(2)RR中,实现了气-液平衡扩散,有效抑制了氢析出副反应.在晶界效应和气-液平衡扩散的协同作用下,优化后的电极在电流密度为700 mA cm^(-2)时,对C_(2)H_(4)和C_(2+).产物的法拉第效率分别高达67.2%和82.1%.此外,C_(2)H_(4)的部分电流密度可高达505 mA cm^(-2),高于大多数文献报道的结果.原位拉曼光谱和衰减全内反射表面增强红外吸收光谱结果表明,丰富的晶;界结构增强了CO_(2)在催化剂表面的活化,显著促进了*CO中间体的形成和吸附,加速了C-C偶联过程形成*OCCO和*OCCOH中间体,提高了C_(2)H_(4)和其他C_(2+)产物的产率.综上,本文设计了一种高活性Cu催化剂和电极结构,为高效电催化CO_(2)还原为C_(2)H_(4)等C_(2+)产物提供参考.展开更多
For the diffusion-controlled adsorption, the expression of dynamic surface adsorption P（t） was ob- tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in t...For the diffusion-controlled adsorption, the expression of dynamic surface adsorption P（t） was ob- tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in this paper. From the measured dynamic surface tension of aqueous surfactant sodium dodecyl sulfate （SDS） solutions at 25 ℃, the adsorption kinetics of SDS at air/solution interface was studied. It was proved that for both of the short and long time limits, the adsorption process of SDS was controlled by diffusion.展开更多
A piston-cylinder apparatus was established to measure the solubility and diffusivity of air in dimethyl silicone oils and in hydraulic oils based on the PVT state equation of air and the solution of unsteady one-dime...A piston-cylinder apparatus was established to measure the solubility and diffusivity of air in dimethyl silicone oils and in hydraulic oils based on the PVT state equation of air and the solution of unsteady one-dimensional diffusion equation.The measured diffusivity-temperature relation can be well fitted by the Arrhenius equation for engineering applications.The correlation between the solute diffusivity D and solvent viscosity μ is examined.In terms of Eyring＇s activation theory,the activation in the air-silicone-oil diffusion process is quite different from that in the momentum transport of the silicone oil：the activation entropy of the former is positive while that of latter is negative.However,the activation enthalpies of the two processes are in the same order of magnitude,which leads to the observation that Dμ/T is roughly constant.展开更多
Separation process undertaken in packed columns often displays anisotropic turbulent mass diffusion. The anisotropic turbulent mass diffusion can be characterized rigorously by using the Reynolds mass flux(RMF) model....Separation process undertaken in packed columns often displays anisotropic turbulent mass diffusion. The anisotropic turbulent mass diffusion can be characterized rigorously by using the Reynolds mass flux(RMF) model.With the RMF model, the concentration and temperature as well as the velocity distributions can be simulated numerically. The modeled Reynolds mass flux equation is adopted to close the turbulent mass transfer equation,while the modeled Reynolds heat flux and Reynolds stress equations are used to close the turbulent heat and momentum transfer equations, so that the Boussinesq postulate and the isotropic assumption are abandoned. To validate the presented RMF model, simulation is carried out for CO2 absorption into aqueous Na OH solutions in a packed column(0.1 m id, packed with 12.7 mm Berl saddles up to a height of 6.55 m). The simulated results are compared with the experimental data and satisfactory agreement is found both in concentration and temperature distributions. The sequel Part II extends the model application to the simulation of an unsteady state adsorption process in a packed column.展开更多
文摘电催化二氧化碳还原反应(CO_(2)RR)可以将二氧化碳转化为具有高经济价值的碳氢化合物,被认为是实现碳中和并缓解能源危机的一种有潜力的技术.铜(Cu)作为一种最有应用前景的非贵金属催化剂之一,表现出较高的催化CO_(2)RR转化为多碳产物(C_(2+))的活性.然而,电催化CO_(2)还原成C_(2+)产物涉及一个动力学过程缓慢的C-C偶联反应,这导致C_(2+)产物的选择性较低,电流密度低,阻碍了其在工业电解槽中的实际应用.同时,CO_(2)RR产物的选择性不仅取决于热力学速率决定步骤,还取决于传质控制动力学.CO_(2)RR发生在固-气-液三相反应界面,气-液的平衡扩散可以有效抑制析氢竞争反应,进而提高CO_(2)RR的反应效率.本文设计合成了一种富晶界的Cu纳米带催化剂,并构建了气-液平衡扩散的电极结构,用于高效电催化二氧化碳还原制备乙烯(C_(2)H_(4)).以一种碱式碳酸铜(Cu_(2)CO_(3)(OH)_(2))纳米带为前驱体,在原位电化学还原条件下,前驱体中的Cu2+离子获得电子被还原为金属Cu,而释放的CO_(3)2-和OH-混合阴离子调节金属Cu的生长.生成的Cu纳米带由细小的纳米颗粒堆积而成,并暴露出大量的由Cu(111),Cu(200)和Cu(220)晶面形成的富晶界结构(GBs).同时,在CO_(2)RR测试中发现催化剂层的厚度是影响CO_(2)和电解质传质的关键因素.通过调整催化层厚度,CO_(2)和电解质可以同时到达催化剂表面,参与到CO_(2)RR中,实现了气-液平衡扩散,有效抑制了氢析出副反应.在晶界效应和气-液平衡扩散的协同作用下,优化后的电极在电流密度为700 mA cm^(-2)时,对C_(2)H_(4)和C_(2+).产物的法拉第效率分别高达67.2%和82.1%.此外,C_(2)H_(4)的部分电流密度可高达505 mA cm^(-2),高于大多数文献报道的结果.原位拉曼光谱和衰减全内反射表面增强红外吸收光谱结果表明,丰富的晶;界结构增强了CO_(2)在催化剂表面的活化,显著促进了*CO中间体的形成和吸附,加速了C-C偶联过程形成*OCCO和*OCCOH中间体,提高了C_(2)H_(4)和其他C_(2+)产物的产率.综上,本文设计了一种高活性Cu催化剂和电极结构,为高效电催化CO_(2)还原为C_(2)H_(4)等C_(2+)产物提供参考.
文摘For the diffusion-controlled adsorption, the expression of dynamic surface adsorption P（t） was ob- tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in this paper. From the measured dynamic surface tension of aqueous surfactant sodium dodecyl sulfate （SDS） solutions at 25 ℃, the adsorption kinetics of SDS at air/solution interface was studied. It was proved that for both of the short and long time limits, the adsorption process of SDS was controlled by diffusion.
基金Supported by the National Natural Science Foundation of China （50675202）
文摘A piston-cylinder apparatus was established to measure the solubility and diffusivity of air in dimethyl silicone oils and in hydraulic oils based on the PVT state equation of air and the solution of unsteady one-dimensional diffusion equation.The measured diffusivity-temperature relation can be well fitted by the Arrhenius equation for engineering applications.The correlation between the solute diffusivity D and solvent viscosity μ is examined.In terms of Eyring＇s activation theory,the activation in the air-silicone-oil diffusion process is quite different from that in the momentum transport of the silicone oil：the activation entropy of the former is positive while that of latter is negative.However,the activation enthalpies of the two processes are in the same order of magnitude,which leads to the observation that Dμ/T is roughly constant.
基金Supported by the National Natural Science Foundation of China(21376163)
文摘Separation process undertaken in packed columns often displays anisotropic turbulent mass diffusion. The anisotropic turbulent mass diffusion can be characterized rigorously by using the Reynolds mass flux(RMF) model.With the RMF model, the concentration and temperature as well as the velocity distributions can be simulated numerically. The modeled Reynolds mass flux equation is adopted to close the turbulent mass transfer equation,while the modeled Reynolds heat flux and Reynolds stress equations are used to close the turbulent heat and momentum transfer equations, so that the Boussinesq postulate and the isotropic assumption are abandoned. To validate the presented RMF model, simulation is carried out for CO2 absorption into aqueous Na OH solutions in a packed column(0.1 m id, packed with 12.7 mm Berl saddles up to a height of 6.55 m). The simulated results are compared with the experimental data and satisfactory agreement is found both in concentration and temperature distributions. The sequel Part II extends the model application to the simulation of an unsteady state adsorption process in a packed column.
