Driven by renewable or excess electrical energy,electrochemical CO_(2)reduction reaction(eCO_(2)RR)represents a promising carbon-neutral approach to generating valuable low-carbon fuels by consuming CO_(2)and H_(2)O.C...Driven by renewable or excess electrical energy,electrochemical CO_(2)reduction reaction(eCO_(2)RR)represents a promising carbon-neutral approach to generating valuable low-carbon fuels by consuming CO_(2)and H_(2)O.C_(2+)products are one of the most economically valuable products among the reduction species of eCO_(2)RR,but there are still some challenges,such as low selectivity or low current density.In this work,we showed that a copper-based metal-azolate framework(MAF),denoted as MAF-203,exhibits the high performance of eCO_(2)RR to yield C_(2+)products with the Faradaic efficiency(C_(2+))of 52.5%and a current density of 660 mA/cm^(2)at-1.2 V vs.RHE in a flow cell device under alkaline condition.Controlled experiment,in situ infrared spectroscopy and the density functional theory(DFT)calculations showed that the electron donating effect of methyl substituents on organic ligands of the copper-based MAF could enhance the ligand field and activation of key intermediates(*CO and*CHO species),thus promoting the coupling of*CO and*CHO for yielding C_(2+)products.展开更多
电化学CO_(2)还原反应(eCO_(2)RR)利用可再生能源将CO_(2)转化为增值化学品,因而得到广泛关注.然而,目前已报道的电催化剂倾向于将CO_(2)转化为HCOOH和CO,而不是增值化学品.金属有机框架(MOF)由于具有较大的比表面积、可调的结构和丰富...电化学CO_(2)还原反应(eCO_(2)RR)利用可再生能源将CO_(2)转化为增值化学品,因而得到广泛关注.然而,目前已报道的电催化剂倾向于将CO_(2)转化为HCOOH和CO,而不是增值化学品.金属有机框架(MOF)由于具有较大的比表面积、可调的结构和丰富的活性位点,已被广泛应用于多相催化、气体储存和气体分离等领域.MOF是研究结构-性能关系的理想平台.金属多氮唑框架(MAF)是一类具有较好化学稳定性的MOF,但在电催化方面的研究很少.本文合成了三种具有相同四铜(Ⅱ)簇单元的金属多氮唑框架(Cu-BTP,Cu-BTTri和Cu-BTT),分别由吡唑、三氮唑和四氮唑衍生配体构成.配体的pKa值依次为H_(3)BTP(pKa=19.8)>H_(3)BTTri(pKa=13.9)>H3BTT(pKa=4.9),表明与BTTri3-和BTT3-相比,BTP3-具有最高的配体场强或配位能力.在相同条件下,对三种MAFs材料进行了电催化CO_(2)还原性能测试.其中,基于吡唑配体的Cu-BTP在流动电解池中电流密度可达1.25 A cm-2,碳氢产物的选择性达到82%(CH_(4)为60%,C_(2)H_(4)为22%).在1.25 A cm-2下连续运行60 h后,催化剂性能未见明显变化.三种MAFs材料对碳氢产物选择性的顺序为Cu-BTP(81%)>Cu-BTTri(60%)>Cu-BTT(49%),与配体的pKa顺序一致,说明配体场的场强对eCO_(2)RR的烃类产物选择性有重要影响.13CO_(2)同位素电化学实验证实了气液产物中的碳来自于CO_(2).X射线衍射图谱、扫描电镜、透射电镜、X射线吸收光谱和X射线光电子能谱结果表明,Cu-BTP具有较好的稳定性.密度泛函理论(DFT)计算揭示了三种MAFs的eCO_(2)RR反应机制.Cu-BTP(Cu:+0.95,N:-0.75)中铜离子和配位氮原子的电荷均低于Cu-BTTri(Cu:+0.99,N:-0.28)和Cu-BTT(Cu:+1.02,N:-0.16),该结果归因于配位N原子周围的电子密度与pKa数值呈正相关.最强的路易斯碱度和配体场场强导致Cu-BTP中金属簇的Cu-N4位点上电子密度最大,因此金属中心的路易斯碱度增强最多.相应地,Cu(Ⅱ)在Cu-BTP中的晶体场稳展开更多
基金supported by the National Key Research and Development Program of China(No.2021YFA1500401)the National Natural Science Foundation of China(Nos.21890380,21821003,22371304,223B2123)+1 种基金the Special Fund Project for Science and Technology Innovation Strategy of Guangdong Province,China(No.STKJ2023078)the Guangzhou Science and Technology Program,China(No.SL2023A04J01767).
文摘Driven by renewable or excess electrical energy,electrochemical CO_(2)reduction reaction(eCO_(2)RR)represents a promising carbon-neutral approach to generating valuable low-carbon fuels by consuming CO_(2)and H_(2)O.C_(2+)products are one of the most economically valuable products among the reduction species of eCO_(2)RR,but there are still some challenges,such as low selectivity or low current density.In this work,we showed that a copper-based metal-azolate framework(MAF),denoted as MAF-203,exhibits the high performance of eCO_(2)RR to yield C_(2+)products with the Faradaic efficiency(C_(2+))of 52.5%and a current density of 660 mA/cm^(2)at-1.2 V vs.RHE in a flow cell device under alkaline condition.Controlled experiment,in situ infrared spectroscopy and the density functional theory(DFT)calculations showed that the electron donating effect of methyl substituents on organic ligands of the copper-based MAF could enhance the ligand field and activation of key intermediates(*CO and*CHO species),thus promoting the coupling of*CO and*CHO for yielding C_(2+)products.
基金financially supported by the National Natural Science Foundation of China(NSFC)(22371033,22175033,and 22266028)the Outstanding Young Technology Talent Foundation of Jilin Province(20230508108RC)+4 种基金the Fundamental Research Funds for the Central Universities(2412019FZ007)the Natural Science Foundation of Hainan Province(823MS062)the Foundation of Xinzhou Teachers University(2021KY07)the Science and Technology Innovation Project of Higher Education in Shanxi Province(2021L450)the Youth Science Research Project of Shanxi Province(202103021223362)。
文摘电化学CO_(2)还原反应(eCO_(2)RR)利用可再生能源将CO_(2)转化为增值化学品,因而得到广泛关注.然而,目前已报道的电催化剂倾向于将CO_(2)转化为HCOOH和CO,而不是增值化学品.金属有机框架(MOF)由于具有较大的比表面积、可调的结构和丰富的活性位点,已被广泛应用于多相催化、气体储存和气体分离等领域.MOF是研究结构-性能关系的理想平台.金属多氮唑框架(MAF)是一类具有较好化学稳定性的MOF,但在电催化方面的研究很少.本文合成了三种具有相同四铜(Ⅱ)簇单元的金属多氮唑框架(Cu-BTP,Cu-BTTri和Cu-BTT),分别由吡唑、三氮唑和四氮唑衍生配体构成.配体的pKa值依次为H_(3)BTP(pKa=19.8)>H_(3)BTTri(pKa=13.9)>H3BTT(pKa=4.9),表明与BTTri3-和BTT3-相比,BTP3-具有最高的配体场强或配位能力.在相同条件下,对三种MAFs材料进行了电催化CO_(2)还原性能测试.其中,基于吡唑配体的Cu-BTP在流动电解池中电流密度可达1.25 A cm-2,碳氢产物的选择性达到82%(CH_(4)为60%,C_(2)H_(4)为22%).在1.25 A cm-2下连续运行60 h后,催化剂性能未见明显变化.三种MAFs材料对碳氢产物选择性的顺序为Cu-BTP(81%)>Cu-BTTri(60%)>Cu-BTT(49%),与配体的pKa顺序一致,说明配体场的场强对eCO_(2)RR的烃类产物选择性有重要影响.13CO_(2)同位素电化学实验证实了气液产物中的碳来自于CO_(2).X射线衍射图谱、扫描电镜、透射电镜、X射线吸收光谱和X射线光电子能谱结果表明,Cu-BTP具有较好的稳定性.密度泛函理论(DFT)计算揭示了三种MAFs的eCO_(2)RR反应机制.Cu-BTP(Cu:+0.95,N:-0.75)中铜离子和配位氮原子的电荷均低于Cu-BTTri(Cu:+0.99,N:-0.28)和Cu-BTT(Cu:+1.02,N:-0.16),该结果归因于配位N原子周围的电子密度与pKa数值呈正相关.最强的路易斯碱度和配体场场强导致Cu-BTP中金属簇的Cu-N4位点上电子密度最大,因此金属中心的路易斯碱度增强最多.相应地,Cu(Ⅱ)在Cu-BTP中的晶体场稳
