二氧化碳(CO_(2))虽然被视为破坏生态环境的温室气体,但也是储量最丰富的碳资源,对其进行转化和利用将对社会环境和能源结构产生深远影响.电化学还原CO_(2)(CO_(2)RR)不仅转化效率高,而且成本较低,有望实现规模化生产.在众多催化剂中,...二氧化碳(CO_(2))虽然被视为破坏生态环境的温室气体,但也是储量最丰富的碳资源,对其进行转化和利用将对社会环境和能源结构产生深远影响.电化学还原CO_(2)(CO_(2)RR)不仅转化效率高,而且成本较低,有望实现规模化生产.在众多催化剂中,廉价易得的铜基催化剂被认为是电化学催化还原CO_(2)生成高附加值产物的理想催化剂之一,其中铜氧化物的存在是CO_(2)RR生成高附加值产物的关键.然而,CO_(2)RR过程是在负电位下进行的,当施加电位低于‒0.1 VRHE时,铜氧化物很容易被还原为金属态铜.因此,催化剂稳定氧化态铜的能力在保持连续、高效和稳定的CO_(2)RR产多碳产物性能中至关重要.本文将简单的O_(2)等离子体处理技术与静电纺丝技术相结合,合成了多孔碳纳米纤维负载的Cu/Cu_(x)O异质结催化剂,并考察了其催化CO_(2)RR的性能.在静电纺丝过程中,Cu-ZIF-8前驱体的加入使得热处理后的原丝纤维中形成了丰富的网络贯穿多孔结构,该结构有效地实现了铜纳米颗粒的均匀分散;随后,通过O_(2)等离子体处理技术,在碳纳米纤维中构建了大量的开放介孔,为CO_(2)的吸附和反应提供了有利环境,并使Cu/Cu_(x)O异质结位点暴露于反应界面.电化学性能测试结果表明,在400 mA cm^(‒2)电流密度下,独特的Cu/Cu_(x)O异质结活性位点电催化还原CO_(2)生成乙醇的法拉第效率可达70.7%,该性能优于未经O_(2)等离子体处理的多孔铜纳米纤维.此外,高暴露的Cu/Cu_(x)O异质结活性位点显著地增加实际参与反应的活性位点数量,经计算Cu/Cu_(x)O异质结CO_(2)RR产乙醇的质量活性高达8.4 A mg^(‒1),是目前报道生产乙醇的较高质量活性.多孔碳纳米纤维衬底不仅具有协同电子输运能力,而且在CO_(2)RR测试中施加的负电压有助于维持Cu/Cu_(x)O异质结构的稳定性,使其在高电流密度下能够保持长时间的催化稳定性.此外,本文利用原位拉曼光谱和红外光谱、有限元模拟及密度泛函理论计算等方法深入研究了Cu/Cu_(x)O异质结的催化机理.原位拉曼光谱和红外光谱表征结果证实了在CO_(2)RR过程中Cu_(x)O的动态稳定状态以及关键信号*CO和C‒C键的存在;理论计算表明,Cu/Cu_(x)O异质结的存在促进了关键中间体*CO的溢流,降低了C‒C耦合过程的反应能垒,从而提高了还原产物乙醇的产率.综上,本文成功地在多孔铜纳米纤维中引入氧化物物种,并优化了纤维孔结构.其表现出了较好的电催化还原CO_(2)性能,可高选择性生成乙醇,其独特的多孔碳纤维结构充分暴露了活性位点,实现了较高的质量活性.本文所采用的催化剂组分和微观结构的调控策略为提升电催化中催化剂稳定性和催化活性提供了有益的借鉴.展开更多
The electrochemical reduction of coumarin at GC electrode in 1-n-butyl-3-methylimidazolium tetrafluoroborate(BMIMBF4) room temperature ionic liquid is reported.Coumarin exhibits a one-electron,irreversible reduction t...The electrochemical reduction of coumarin at GC electrode in 1-n-butyl-3-methylimidazolium tetrafluoroborate(BMIMBF4) room temperature ionic liquid is reported.Coumarin exhibits a one-electron,irreversible reduction to caroanion radical,and the latter species undergoes fast dimerization to dihydrodimer.The influences of scan rate, concentration and temperature were studied by cyclic voltammetry.The results show that the reaction is diffusion controlled.The diffusion coefficient D of coumarin in BMIMBF4 from Chronocoulometry is 5.066×10-7 cm2/s. Furthermore,the influences of water and substituting group during the electroreduction are discussed. These preliminary electrochemical experiments show encouraging results for the use of ionic liquids in a 'green' electrochemistry.展开更多
基金financially supported by the National Natural Science Foundation of China(No.22273093)the CAS Project for Young Scientists in Basic Re-search(YSBR-005)the start-up funding of University of Science and Technology of China。
文摘二氧化碳(CO_(2))虽然被视为破坏生态环境的温室气体,但也是储量最丰富的碳资源,对其进行转化和利用将对社会环境和能源结构产生深远影响.电化学还原CO_(2)(CO_(2)RR)不仅转化效率高,而且成本较低,有望实现规模化生产.在众多催化剂中,廉价易得的铜基催化剂被认为是电化学催化还原CO_(2)生成高附加值产物的理想催化剂之一,其中铜氧化物的存在是CO_(2)RR生成高附加值产物的关键.然而,CO_(2)RR过程是在负电位下进行的,当施加电位低于‒0.1 VRHE时,铜氧化物很容易被还原为金属态铜.因此,催化剂稳定氧化态铜的能力在保持连续、高效和稳定的CO_(2)RR产多碳产物性能中至关重要.本文将简单的O_(2)等离子体处理技术与静电纺丝技术相结合,合成了多孔碳纳米纤维负载的Cu/Cu_(x)O异质结催化剂,并考察了其催化CO_(2)RR的性能.在静电纺丝过程中,Cu-ZIF-8前驱体的加入使得热处理后的原丝纤维中形成了丰富的网络贯穿多孔结构,该结构有效地实现了铜纳米颗粒的均匀分散;随后,通过O_(2)等离子体处理技术,在碳纳米纤维中构建了大量的开放介孔,为CO_(2)的吸附和反应提供了有利环境,并使Cu/Cu_(x)O异质结位点暴露于反应界面.电化学性能测试结果表明,在400 mA cm^(‒2)电流密度下,独特的Cu/Cu_(x)O异质结活性位点电催化还原CO_(2)生成乙醇的法拉第效率可达70.7%,该性能优于未经O_(2)等离子体处理的多孔铜纳米纤维.此外,高暴露的Cu/Cu_(x)O异质结活性位点显著地增加实际参与反应的活性位点数量,经计算Cu/Cu_(x)O异质结CO_(2)RR产乙醇的质量活性高达8.4 A mg^(‒1),是目前报道生产乙醇的较高质量活性.多孔碳纳米纤维衬底不仅具有协同电子输运能力,而且在CO_(2)RR测试中施加的负电压有助于维持Cu/Cu_(x)O异质结构的稳定性,使其在高电流密度下能够保持长时间的催化稳定性.此外,本文利用原位拉曼光谱和红外光谱、有限元模拟及密度泛函理论计算等方法深入研究了Cu/Cu_(x)O异质结的催化机理.原位拉曼光谱和红外光谱表征结果证实了在CO_(2)RR过程中Cu_(x)O的动态稳定状态以及关键信号*CO和C‒C键的存在;理论计算表明,Cu/Cu_(x)O异质结的存在促进了关键中间体*CO的溢流,降低了C‒C耦合过程的反应能垒,从而提高了还原产物乙醇的产率.综上,本文成功地在多孔铜纳米纤维中引入氧化物物种,并优化了纤维孔结构.其表现出了较好的电催化还原CO_(2)性能,可高选择性生成乙醇,其独特的多孔碳纤维结构充分暴露了活性位点,实现了较高的质量活性.本文所采用的催化剂组分和微观结构的调控策略为提升电催化中催化剂稳定性和催化活性提供了有益的借鉴.
文摘The electrochemical reduction of coumarin at GC electrode in 1-n-butyl-3-methylimidazolium tetrafluoroborate(BMIMBF4) room temperature ionic liquid is reported.Coumarin exhibits a one-electron,irreversible reduction to caroanion radical,and the latter species undergoes fast dimerization to dihydrodimer.The influences of scan rate, concentration and temperature were studied by cyclic voltammetry.The results show that the reaction is diffusion controlled.The diffusion coefficient D of coumarin in BMIMBF4 from Chronocoulometry is 5.066×10-7 cm2/s. Furthermore,the influences of water and substituting group during the electroreduction are discussed. These preliminary electrochemical experiments show encouraging results for the use of ionic liquids in a 'green' electrochemistry.
