面向国家绿色低碳战略目标,变革化石资源合成氨技术路线变得尤为迫切,开发可再生能源制“绿氨”将成为合成氨领域未来的重要发展方向.将工业废水中的硝酸根(NO_(3)-)电催化还原为氨(NO_(3)RR),既可有效回收氨,又能消除硝酸根污染影响.然...面向国家绿色低碳战略目标,变革化石资源合成氨技术路线变得尤为迫切,开发可再生能源制“绿氨”将成为合成氨领域未来的重要发展方向.将工业废水中的硝酸根(NO_(3)-)电催化还原为氨(NO_(3)RR),既可有效回收氨,又能消除硝酸根污染影响.然而,NO_(3)RR涉及缓慢的八电子转移过程,含有多种反应中间体,其反应机理复杂不明.此外,水系电解液中存在的析氢竞争反应也为高效NO_(3)RR催化剂的开发设计带来了巨大的挑战.为突破高效催化剂的发展瓶颈,本文通过理论模拟,在低成本的催化剂上设计了高效的NO_(3)RR催化活性位点,并利用简单的制备策略合成了目标催化剂.同时,结合原位表征技术,阐明了NO_(3)RR的反应路径及催化机理.本文通过密度泛函理论(DFT)计算发现,Cu/TiO_(2)催化剂上的Cu-O-Ti-O_(v)结构具有较好的NO_(3)-还原活性,该结构不仅能够促进反应中间体NOx-的吸附和活化,还能有效抑制竞争析氢反应,从而降低NO_(3)RR的反应能垒.在该结构上,NO_(3)RR的反应路径为:NO_(3)^(*)→NO_(2)^(*)→HONO^(*)→NO^(*)→*NOH→*N→^(*)NH→*NH2→*NH_(3)→NH_(3).基于理论计算结果,分别采用浸渍法和尿素水解法制备了系列富含Cu-O-Ti-O_(v)结构的Cu/TiO_(2)催化剂.氮气等温吸附-脱附曲线、拉曼光谱(Raman)、电子顺磁共振波谱、X射线光电子能谱(XPS)和傅立叶红外光谱等结果发现,相比于采用浸渍法制备的系列Cu/TiO_(2)催化剂,采用尿素水解法制备的Cu/TiO_(2)(CT-U)催化剂具有更大的比表面积以及更多的Cu-O-Ti-O_(v)位点,说明尿素水解法可提高Cu颗粒在TiO_(2)载体表面的分散度,增强Cu颗粒与TiO_(2)载体之间的相互作用,提高Cu/TiO_(2)催化剂表面的Cu-O-Ti-O_(v)位点含量.将以上制备出的催化剂应用于催化NO_(3)RR中,结果表明,在-1.0 V vs.RHE还原电位下,CT-U催化剂上氨产率可达3046.5μg h^(-1) mgcat^(-1),高于大多数文献报道结果.循环稳定性测试结果表明,在Cu/TiO_(2)催化剂上构建Cu-O-Ti-O_(v)位点还能显著抑制电催化反应过程中Cu物种从Cu/TiO_(2)催化剂上溶出,从而显著增强催化剂的稳定性.此外,设计制备了不含氧空位的Cu/TiO_(2),TiO_(2)-x,Cu,Cu_(2)O以及CuO催化剂,并将其用于催化NO_(3)RR.结果发现,上述催化剂上的氨产率皆明显低于CT-U催化剂,说明Cu,Ti以及O_(v)构成的Cu-O-Ti-O_(v)结构具有较好的催化协同作用,从而显著提升了NO_(3)RR反应活性.最后,通过原位Raman及原位XPS表征检测反应中间体,验证了由DFT模拟出的NO_(3)RR反应路径.综上,通过在Cu/TiO_(2)催化剂上理论指导构建Cu-O-Ti-O_(v)活性位点,实现了NO_(3)RR性能的有效提升.Cu-O-Ti-O_(v)结构中的多位点协同作用不仅促进了NO_(x)-的吸附和活化,而且抑制了电催化过程中Cu物种从催化剂上的溶出,从而提高了催化剂的稳定性.本研究为设计高效稳定的NO_(3)RR催化剂提供了新思路.展开更多
Electrocatalytic reduction of CO_(2)(CO_(2)RR)to multicarbon products is an efficient approach for ad-dressing the energy crisis and achieving carbon neutrality.In H-cells,achieving high-current C_(2)products is chall...Electrocatalytic reduction of CO_(2)(CO_(2)RR)to multicarbon products is an efficient approach for ad-dressing the energy crisis and achieving carbon neutrality.In H-cells,achieving high-current C_(2)products is challenging because of the inefficient mass transfer of the catalyst and the presence of the hydrogen evolution reaction(HER).In this study,dendritic Cu/Cu_(2)O with abundant Cu^(0)/Cu^(+)interfaces and numerous dendritic curves was synthesized in a CO_(2)atmosphere,resulting in the high selectivity and current density of the C_(2)products.Dendritic Cu/Cu_(2)O achieved a C_(2)Faradaic efficiency of 69.8%and a C_(2)partial current density of 129.5 mA cm^(-2)in an H-cell.Finite element simulations showed that a dendritic structure with a high curvature generates a strong electric field,leading to a localized CO_(2)concentration.Additionally,DRT analysis showed that a dendritic struc-ture with a high curvature actively adsorbed the surrounding high concentration of CO_(2),enhancing the mass transfer rate and achieving a high current density.During the experiment,the impact of the electronic structure on the performance of the catalyst was investigated by varying the atomic ratio of Cu^(0)/Cu^(+) on the catalyst surface,which resulted in improved ethylene selectivity.Under the optimal atomic ratio of Cu^(0)/Cu^(+),the charge transfer resistance was minimized,and the desorption rate of the intermediates was low,favoring C_(2) generation.Density functional theory calculations indicated that the Cu^(0)/Cu^(+) interfaces exhibited a lower Gibbs free energy for the rate-determining step,enhancing C_(2)H_(4) formation.The Cu/Cu_(2)O catalyst also exhibited a low Cu d-band center,which enhanced the adsorption stability of *CO on the surface and facilitated C_(2)formation.This observa-tion explained the higher yield of C_(2) products at the Cu^(0)/Cu^(+) interface than that of H_(2) under rapid mass transfer.The results of the net present value model showed that the H-cell holds promising industrial prospects,contingent upon it being a catalyst with both high selectivity and high current density.This approach of integrating the structure and composition provides new insights for ad-vancing the CO_(2)RR towards high-current C_(2) products.展开更多
H_(2)O吸附引起的二次电子发射增强是导致真空微波器件与设备异常放电的关键因素。为了研究H_(2)O吸附对金属表面二次电子发射特性的影响规律,该文考虑电子−H_(2)O分子碰撞的7种散射类型,采用Monte Carlo方法模拟电子−H_(2)O吸附分子的...H_(2)O吸附引起的二次电子发射增强是导致真空微波器件与设备异常放电的关键因素。为了研究H_(2)O吸附对金属表面二次电子发射特性的影响规律,该文考虑电子−H_(2)O分子碰撞的7种散射类型,采用Monte Carlo方法模拟电子−H_(2)O吸附分子的散射过程,同时考虑功函数变化对电子出射概率的影响,建立了一种H_(2)O吸附Cu表面的二次电子发射模型,统计二次电子的最终状态,并对二次电子发射系数(secondary electron yield,SEY)和二次电子能谱(secondary electron spectrum,SES)的变化规律进行分析。结果表明,H_(2)O吸附能够降低表面功函数,且产生更多电离电子,导致SEY增大;但当吸附厚度大于100 nm时,SEY不再继续增大,这是由于吸附层较厚时,电子无法进入Cu基底,仅在吸附层内散射。SES的谱峰随着吸附厚度的增加而增强,表明H_(2)O能够促使更多的低能电子出射,这是造成二次电子发射增强的重要因素。该文的模型为研究复杂表面状态的二次电子发射提供了可靠的分析方法,相关结果能够用于分析解释真空微波器件与设备放电形成机理,优化设备部件的设计参数。展开更多
用柠檬酸络合法制备了钙钛矿型 La Fe O3及 La Fe1 - x Cux O3化合物 ,测定了其对酸性红 3B等水溶性染料的光催化降解活性 .利用红外、紫外和光声光谱、正电子寿命谱及光电子能谱等技术分析了 La Fe O3的光催化性能及掺杂对其活性的影...用柠檬酸络合法制备了钙钛矿型 La Fe O3及 La Fe1 - x Cux O3化合物 ,测定了其对酸性红 3B等水溶性染料的光催化降解活性 .利用红外、紫外和光声光谱、正电子寿命谱及光电子能谱等技术分析了 La Fe O3的光催化性能及掺杂对其活性的影响 .结果表明 ,掺杂 Cu2 + 可使 La Fe展开更多
The efect of CO2 on catalytic activity for CO oxidation on Cu-Ce-O fluorite-type complex oxides has been investigated. CO2 played an inhibiting role in CO oxidation on the cat-alyst simlar to what happened on CeO2. As...The efect of CO2 on catalytic activity for CO oxidation on Cu-Ce-O fluorite-type complex oxides has been investigated. CO2 played an inhibiting role in CO oxidation on the cat-alyst simlar to what happened on CeO2. As CO2 was introduced into the feed, the coliversion of CO to CO2 on the catalyst was reduced a little. At room temperature,the catalyst could easily adsorb CO2 in large amounts from the air to fbrm carbonate on its surtace.as well as from the yields at low reaction temperature As a restit,the catalyst could be poisoned by CO2 tentatively.The catalytic activity could be recovered to its imitial value on being heated at 300 ℃ or highertemperature.Cu-Ce-O catalyst showed high activity with CO conversion over 98% after being pretreated to desorb CO2 previously.展开更多
文摘面向国家绿色低碳战略目标,变革化石资源合成氨技术路线变得尤为迫切,开发可再生能源制“绿氨”将成为合成氨领域未来的重要发展方向.将工业废水中的硝酸根(NO_(3)-)电催化还原为氨(NO_(3)RR),既可有效回收氨,又能消除硝酸根污染影响.然而,NO_(3)RR涉及缓慢的八电子转移过程,含有多种反应中间体,其反应机理复杂不明.此外,水系电解液中存在的析氢竞争反应也为高效NO_(3)RR催化剂的开发设计带来了巨大的挑战.为突破高效催化剂的发展瓶颈,本文通过理论模拟,在低成本的催化剂上设计了高效的NO_(3)RR催化活性位点,并利用简单的制备策略合成了目标催化剂.同时,结合原位表征技术,阐明了NO_(3)RR的反应路径及催化机理.本文通过密度泛函理论(DFT)计算发现,Cu/TiO_(2)催化剂上的Cu-O-Ti-O_(v)结构具有较好的NO_(3)-还原活性,该结构不仅能够促进反应中间体NOx-的吸附和活化,还能有效抑制竞争析氢反应,从而降低NO_(3)RR的反应能垒.在该结构上,NO_(3)RR的反应路径为:NO_(3)^(*)→NO_(2)^(*)→HONO^(*)→NO^(*)→*NOH→*N→^(*)NH→*NH2→*NH_(3)→NH_(3).基于理论计算结果,分别采用浸渍法和尿素水解法制备了系列富含Cu-O-Ti-O_(v)结构的Cu/TiO_(2)催化剂.氮气等温吸附-脱附曲线、拉曼光谱(Raman)、电子顺磁共振波谱、X射线光电子能谱(XPS)和傅立叶红外光谱等结果发现,相比于采用浸渍法制备的系列Cu/TiO_(2)催化剂,采用尿素水解法制备的Cu/TiO_(2)(CT-U)催化剂具有更大的比表面积以及更多的Cu-O-Ti-O_(v)位点,说明尿素水解法可提高Cu颗粒在TiO_(2)载体表面的分散度,增强Cu颗粒与TiO_(2)载体之间的相互作用,提高Cu/TiO_(2)催化剂表面的Cu-O-Ti-O_(v)位点含量.将以上制备出的催化剂应用于催化NO_(3)RR中,结果表明,在-1.0 V vs.RHE还原电位下,CT-U催化剂上氨产率可达3046.5μg h^(-1) mgcat^(-1),高于大多数文献报道结果.循环稳定性测试结果表明,在Cu/TiO_(2)催化剂上构建Cu-O-Ti-O_(v)位点还能显著抑制电催化反应过程中Cu物种从Cu/TiO_(2)催化剂上溶出,从而显著增强催化剂的稳定性.此外,设计制备了不含氧空位的Cu/TiO_(2),TiO_(2)-x,Cu,Cu_(2)O以及CuO催化剂,并将其用于催化NO_(3)RR.结果发现,上述催化剂上的氨产率皆明显低于CT-U催化剂,说明Cu,Ti以及O_(v)构成的Cu-O-Ti-O_(v)结构具有较好的催化协同作用,从而显著提升了NO_(3)RR反应活性.最后,通过原位Raman及原位XPS表征检测反应中间体,验证了由DFT模拟出的NO_(3)RR反应路径.综上,通过在Cu/TiO_(2)催化剂上理论指导构建Cu-O-Ti-O_(v)活性位点,实现了NO_(3)RR性能的有效提升.Cu-O-Ti-O_(v)结构中的多位点协同作用不仅促进了NO_(x)-的吸附和活化,而且抑制了电催化过程中Cu物种从催化剂上的溶出,从而提高了催化剂的稳定性.本研究为设计高效稳定的NO_(3)RR催化剂提供了新思路.
文摘Electrocatalytic reduction of CO_(2)(CO_(2)RR)to multicarbon products is an efficient approach for ad-dressing the energy crisis and achieving carbon neutrality.In H-cells,achieving high-current C_(2)products is challenging because of the inefficient mass transfer of the catalyst and the presence of the hydrogen evolution reaction(HER).In this study,dendritic Cu/Cu_(2)O with abundant Cu^(0)/Cu^(+)interfaces and numerous dendritic curves was synthesized in a CO_(2)atmosphere,resulting in the high selectivity and current density of the C_(2)products.Dendritic Cu/Cu_(2)O achieved a C_(2)Faradaic efficiency of 69.8%and a C_(2)partial current density of 129.5 mA cm^(-2)in an H-cell.Finite element simulations showed that a dendritic structure with a high curvature generates a strong electric field,leading to a localized CO_(2)concentration.Additionally,DRT analysis showed that a dendritic struc-ture with a high curvature actively adsorbed the surrounding high concentration of CO_(2),enhancing the mass transfer rate and achieving a high current density.During the experiment,the impact of the electronic structure on the performance of the catalyst was investigated by varying the atomic ratio of Cu^(0)/Cu^(+) on the catalyst surface,which resulted in improved ethylene selectivity.Under the optimal atomic ratio of Cu^(0)/Cu^(+),the charge transfer resistance was minimized,and the desorption rate of the intermediates was low,favoring C_(2) generation.Density functional theory calculations indicated that the Cu^(0)/Cu^(+) interfaces exhibited a lower Gibbs free energy for the rate-determining step,enhancing C_(2)H_(4) formation.The Cu/Cu_(2)O catalyst also exhibited a low Cu d-band center,which enhanced the adsorption stability of *CO on the surface and facilitated C_(2)formation.This observa-tion explained the higher yield of C_(2) products at the Cu^(0)/Cu^(+) interface than that of H_(2) under rapid mass transfer.The results of the net present value model showed that the H-cell holds promising industrial prospects,contingent upon it being a catalyst with both high selectivity and high current density.This approach of integrating the structure and composition provides new insights for ad-vancing the CO_(2)RR towards high-current C_(2) products.
文摘H_(2)O吸附引起的二次电子发射增强是导致真空微波器件与设备异常放电的关键因素。为了研究H_(2)O吸附对金属表面二次电子发射特性的影响规律,该文考虑电子−H_(2)O分子碰撞的7种散射类型,采用Monte Carlo方法模拟电子−H_(2)O吸附分子的散射过程,同时考虑功函数变化对电子出射概率的影响,建立了一种H_(2)O吸附Cu表面的二次电子发射模型,统计二次电子的最终状态,并对二次电子发射系数(secondary electron yield,SEY)和二次电子能谱(secondary electron spectrum,SES)的变化规律进行分析。结果表明,H_(2)O吸附能够降低表面功函数,且产生更多电离电子,导致SEY增大;但当吸附厚度大于100 nm时,SEY不再继续增大,这是由于吸附层较厚时,电子无法进入Cu基底,仅在吸附层内散射。SES的谱峰随着吸附厚度的增加而增强,表明H_(2)O能够促使更多的低能电子出射,这是造成二次电子发射增强的重要因素。该文的模型为研究复杂表面状态的二次电子发射提供了可靠的分析方法,相关结果能够用于分析解释真空微波器件与设备放电形成机理,优化设备部件的设计参数。
文摘用柠檬酸络合法制备了钙钛矿型 La Fe O3及 La Fe1 - x Cux O3化合物 ,测定了其对酸性红 3B等水溶性染料的光催化降解活性 .利用红外、紫外和光声光谱、正电子寿命谱及光电子能谱等技术分析了 La Fe O3的光催化性能及掺杂对其活性的影响 .结果表明 ,掺杂 Cu2 + 可使 La Fe
文摘The efect of CO2 on catalytic activity for CO oxidation on Cu-Ce-O fluorite-type complex oxides has been investigated. CO2 played an inhibiting role in CO oxidation on the cat-alyst simlar to what happened on CeO2. As CO2 was introduced into the feed, the coliversion of CO to CO2 on the catalyst was reduced a little. At room temperature,the catalyst could easily adsorb CO2 in large amounts from the air to fbrm carbonate on its surtace.as well as from the yields at low reaction temperature As a restit,the catalyst could be poisoned by CO2 tentatively.The catalytic activity could be recovered to its imitial value on being heated at 300 ℃ or highertemperature.Cu-Ce-O catalyst showed high activity with CO conversion over 98% after being pretreated to desorb CO2 previously.
