钴席夫碱配合物电催化还原CO_2研究
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摘要
报道了3例含不同官能团的单核席夫碱(N,N'-双(水杨醛)-1,2-苯二胺)钴(Ⅱ)配合物在无水有机溶剂和在含10%H_2O的有机溶剂中的电催化还原CO_2性能.同时,通过研究配合物电子效应对其催化性能影响实验发现:具有吸电子基团(-F)的配合物1表现出最低的催化起始电位(Eonset=-1.55 V相对于Ag/AgCl),而具有给电子基团(-OCH3)的配合物3则具有最高的催化活性,其催化转换频率和法拉第效率分别为620 s-1和68.5%.以上结果表明,钴席夫碱配合物具有高活性和高选择性电催化还原CO_2性能,而且通过对分子催化剂电子效应的调控可以实现对其催化活性的优化.
The electrocatalytic reduction of carbon dioxide to value-added chemical fuels is an important project in green and energy chemistry.In the current study,the electrocatalytic performance for CO_2 reduction driven by three mononuclear Co(Ⅱ) complexes containing salophen(salophen=N,N'-bis(salicylaldheyde)-1,2-phenyldiamine)ligands with various substitutes were examined in dry organic homogeneous medium and the mixture solution containing 10% H_2O(V/V),respectively.Furthermore,the electronic effects of complexes on catalytic activities were investigated.Complex 1 with electron-withdrawing groups(-F) emerged as a catalyst with the lowest catalytic onset potential(Eonset=-1.55 V vs Ag/AgCl);whereas complex 3 with electron-donating groups(-OCH3)had the highest catalytic activity and achieved turnover frequency and Faradaic efficiency of 620 s-1 and 68.5%,respectively.The results indicated that these cobalt schiff base complexes have high activity and selectivity for the electrocatalytic reduction of CO_2 to CO,and the catalytic performances of these complexes could be rationally optimized in terms of electronic effects from their ligands.
The electrocatalytic reduction of carbon dioxide to value-added chemical fuels is an important project in green and energy chemistry.In the current study,the electrocatalytic performance for CO_2 reduction driven by three mononuclear Co(Ⅱ) complexes containing salophen(salophen=N,N'-bis(salicylaldheyde)-1,2-phenyldiamine)ligands with various substitutes were examined in dry organic homogeneous medium and the mixture solution containing 10% H_2O(V/V),respectively.Furthermore,the electronic effects of complexes on catalytic activities were investigated.Complex 1 with electron-withdrawing groups(-F) emerged as a catalyst with the lowest catalytic onset potential(Eonset=-1.55 V vs Ag/AgCl);whereas complex 3 with electron-donating groups(-OCH3)had the highest catalytic activity and achieved turnover frequency and Faradaic efficiency of 620 s-1 and 68.5%,respectively.The results indicated that these cobalt schiff base complexes have high activity and selectivity for the electrocatalytic reduction of CO_2 to CO,and the catalytic performances of these complexes could be rationally optimized in terms of electronic effects from their ligands.
引文
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[21]Agarwal J,Shaw T W,Stanton C J,et al.Revealing the origin of activity in nitrogen-doped nanocarbons towards electrocatalytic reduction of carbon dioxide[J].Angewandte Chemie(International Edition),2014,126:5252-5255.
[22]Smieja J M,Sampson M D,Grice K A,et al.Manganese as a substitute for rhenium in CO2 reduction catalysts:The importance of acids[J].Inorganic Chemistry,2013,52:2484-2491.
[2]Aresta M,Dibenedetto A,Angelini A.Catalysis for the valorization of exhaust carbon:From CO2 to chemicals,materials,and fuels technological use of CO2[J].Chemical Reviews,2014,114:1709-1742.
[3]Schwarz H A,Dodson R W.Reduction potentials of CO2·-and the alcohol radicals[J].The Journal of Physical Chemistry,1989,93:409-414.
[4]Fujita E.Photochemical carbon dioxide reduction with metal complexes[J].Coordination Chemistry Reviews,1999(185/186):373-384.
[5]Costentin C,Drouet S,Robert M,et al.A local proton source enhances CO2 electroreduction to CO by a molecular Fe catalyst[J].Science,2012,338:90-94.
[6]Grodkowski J,Neta P,Fujita E,et al.Reduction of cobalt and iron corroles and catalyzed reduction of CO2[J].The Journal of Physical Chemistry A,2002,106:4772-4778.
[7]Fisher B J,Eisenberg R.Electrocatalytic reduction of carbon dioxide by using macrocycles of nickel and cobalt[J].Journal of the American Chemical Society,1980,102:7361-7363.
[8]Froehlich J D,Kubiak C P.Homogeneous CO2 reduction by Ni(cyclam)at a glassy carbon electrode[J].Inorganic Chemistry,2012,51:3932-3934.
[9]Smieja J M,Kubiak C P.Re(bipy-t Bu)(CO)3Cl-improved catalytic activity for reduction of carbon dioxide:IR-spectroelectrochemical and mechanistic studies[J].Inorganic Chemistry,2010,49:9283-9289.
[10]Wang W,Hull J F,Muckerman J T,et al.Secondcoordination-sphere and electronic effects enhance iridium(III)-catalyzed homogeneous hydrogenation of carbon dioxide in water near ambient temperature and pressure[J].Energy&Environmental Science,2012,5:7923-7926.
[11]Morris A J,Meyer G J,Fujita E.Molecular approaches to the photocatalytic reduction of carbon dioxide for solar fuels[J].Accounts of Chemical Research,2009,42:1983-1994.
[12]Hawecker J,Lehn J M,Ziessel R.Photochemical and electrochemical reduction of carbon dioxide to carbon monoxide mediated by(2,2'‐bipyridine)(I)and related complexes as homogeneous catalysts[J].Helvetica Chimica Acta,1986,69:1990-2012.
[13]Windle C D,Perutz R N.Advances in molecular photocatalytic and electrocatalytic CO2 reduction[J].Coordination Chemistry Reviews,2012,256:2562-2570.
[14]Pearce D J,Pletcher D.A study of the mechanism for the electrocatalysis of carbon dioxide reduction by nickel and cobalt square planar complexes in solution[J].Journal of Electroanalytical Chemistry and Interfacial Electrochemistry,1986,197:317-330.
[15]Isse A A,Gennaro A,Vianello E.Electrochemical reduction of carbon dioxide catalyzed by[Co I(salophen)Li][J].Journal of Molecular Catalysis,1991,70:197-208.
[16]Losada J,del Peso I,Beyer L,et al.Electrocatalytic reduction of O2 and CO2 with electropolymerized films of polypyrrole cobalt(II)Schiff-base complexes[J].Journal of Electroanalytical Chemistry,1995,398:89-93.
[17]Isse A A,Gennaro A,Vianello E.The electrochemical reduction mechanism of[N,N'-1,2-phenylenebis(salicylideneiminato)]cobalt(II)[J].Journal of the Chemical Society Dalton Transactions,1993,14:2091-2096.
[18]Isse A A,Cennaro A,Vianello E.Electrochemical reduction of schiff base ligands H2salen and H2salophen[J].Electrochimica Acta,1997,42:2065-2071.
[19]Thoi V S,Chang C J.Nickel N-heterocyclic carbinepyridine complexes that exhibit selectivity for electrocatalytic reduction of carbon dioxide over water[J].Chemical Communications,2011,47:6578-6580.
[20]Thoi V S,Kornienko N,Margarit C G,et al.Visible-light photoredox catalysis:Selective reduction of carbon dioxide to carbon monoxide by a nickel N-heterocyclic carbine-isoquinoline complex[J].Journal of the American Chemical Society,2013,135:14413-14424.
[21]Agarwal J,Shaw T W,Stanton C J,et al.Revealing the origin of activity in nitrogen-doped nanocarbons towards electrocatalytic reduction of carbon dioxide[J].Angewandte Chemie(International Edition),2014,126:5252-5255.
[22]Smieja J M,Sampson M D,Grice K A,et al.Manganese as a substitute for rhenium in CO2 reduction catalysts:The importance of acids[J].Inorganic Chemistry,2013,52:2484-2491.