钴盐阴离子基团对Co-N-C催化剂电催化活性的影响
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摘要
采用化学氧化法在苯胺聚合过程中分别加入钴(Co)为Co2+而阴离子基团为(C2H3O2)22-、Cl22-、(NO3)22-、SO42-及C2O42-的乙酸钴、氯化钴、硝酸钴、硫酸钴、草酸钴等钴盐,合成出不同聚苯胺-钴(PANI-Co)配位聚合物。然后将PANI-Co聚合物作为前驱体在N2气氛中900℃热处理,制备出氮掺杂的Co-N-C碳基催化剂。采用SEM、XRD、XPS、Raman等手段分析Co-N-C催化剂的形貌、结构、化学组成及化学价态,并采用电化学方法测试了Co-N-C催化剂的电催化活性。结果表明,Co盐的阴离子基团对Co-N-C催化剂的形貌影响不大,但对Co-N-C催化剂中表面化学组成及含量、碳结构、石墨化程度以及Co的价态影响较大,并且Co盐的阴离子基团会影响Co-N-C催化剂的电催化活性,其氧还原(ORR)活性按照(C2H3O2)22->Cl22->(NO3)22->SO42->C2O42-顺序降低。含(C2H3O2)22-和Cl22-阴离子的钴盐制备的Co-N-C催化剂具有较高的ORR活性,这可能源于其较高含量的石墨氮和吡啶氮。
During the process of the aniline polymerization,bivalent cobalt salt with different anionic groups such as(C2 H3 O2)22-,Cl22-,(NO3)22-,SO42-and C2 O42-were added into the solution and then different polyaniline cobalt(PANI-Co)coordination polymer were obtained.Finally,Co-N-C catalysts were prepared through pyrolysis of PANI-Co coordination polymer.The morphology,structure,chemical composition and chemical valence of the Co-N-C catalysts were characterized by scanning electron microscopy(SEM),X-ray spectroscopy(XRD),X-ray photoelectron spectroscopy(XPS)and Raman spectra(Raman).The electrocatalytic activity of Co-N-C catalysts were tested by electrochemical method.The results showed that the cobalt salt anionic groups had little impact on the morphology of Co-N-C catalysts,but had a great influence on the composition and surface chemistry of Co-N-C catalysts,carbon structure,degree of graphitization and the valence of Co.The cobalt salt anionic groups could affect the electrocatalytic activity of Co-N-C catalysts.The catalytic activities decreased as(C2 H3 O2)22->Cl22->(NO3)22->SO42->C2 O42-.The Co-N-C catalysts prepared by cobalt salt containing(C2 H3 O2)22-and Cl22-anions had higher ORR activity,which possibly due to the higher content of graphite nitrogen and pyridine nitrogen.
During the process of the aniline polymerization,bivalent cobalt salt with different anionic groups such as(C2 H3 O2)22-,Cl22-,(NO3)22-,SO42-and C2 O42-were added into the solution and then different polyaniline cobalt(PANI-Co)coordination polymer were obtained.Finally,Co-N-C catalysts were prepared through pyrolysis of PANI-Co coordination polymer.The morphology,structure,chemical composition and chemical valence of the Co-N-C catalysts were characterized by scanning electron microscopy(SEM),X-ray spectroscopy(XRD),X-ray photoelectron spectroscopy(XPS)and Raman spectra(Raman).The electrocatalytic activity of Co-N-C catalysts were tested by electrochemical method.The results showed that the cobalt salt anionic groups had little impact on the morphology of Co-N-C catalysts,but had a great influence on the composition and surface chemistry of Co-N-C catalysts,carbon structure,degree of graphitization and the valence of Co.The cobalt salt anionic groups could affect the electrocatalytic activity of Co-N-C catalysts.The catalytic activities decreased as(C2 H3 O2)22->Cl22->(NO3)22->SO42->C2 O42-.The Co-N-C catalysts prepared by cobalt salt containing(C2 H3 O2)22-and Cl22-anions had higher ORR activity,which possibly due to the higher content of graphite nitrogen and pyridine nitrogen.
引文
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3 Bing L,Higgins D C,Xiao Q,et al.The durability of carbon supported Pt nanowire as novel cathode catalyst for a 1.5kW PEMFC stack[J].Applied Catalysis B:Environmental,2015,162:133.
4 Ohyagi S,Sasaki T.Durability of a PEMFC Pt-Co cathode catalyst layer during voltage cycling tests under supersaturated humidity conditions[J].Electrochimica Acta,2013,102(102):336.
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6 Ding W,Li L,Xiong K,et al.Shape fixing via salt recrystallization:A morphology-controlled approach to convert nanostructured polymer to carbon nanomaterial as a highly active catalyst for oxygen reduction reaction[J].Journal of the American Chemical Society,2015,137(16):5414.
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9 Deng D,Yu L,Chen X,et al.Iron encapsulated within pod-like carbon nanotubes for oxygen reduction reaction[J].Angewandte Chemie International Edition,2013,52(1):371.
10 Hu Y,Jensen J O,Zhang W,et al.Hollow spheres of iron carbide nanoparticles encased in graphitic layers as oxygen reduction catalysts[J].Angewandte Chemie International Edition,2014,53(14):3675.
11 Elumeeva K,Ren J,Antonietti M,et al.High surface iron/cobaltcontaining nitrogen-doped carbon aerogels as non-precious advanced electrocatalysts for oxygen reduction[J].ChemElectroChem,2015,2(4):584.
12 Wang Y,Nie Y,Wei Z D.Unification of catalytic oxygen reduction and hydrogen evolution reactions:Highly dispersive Co nanoparticles encapsulated inside Co and nitrogen co-doped carbon[J].Chemical Communications,2015,51(43):8942.
13 Yang R,Stevens K,Dahn J R.Investigation of activity of sputtered transition-metal(TM)-C-N(TM=V,Cr,Mn,Co,Ni)catalysts for oxygen reduction reaction[J].Journal of the Electrochemical Society,2008,155(1):B79.
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15 Lefèvre M,Proietti E,Jaouen F,et al.Iron-based catalysts with improved oxygen reduction activity in polymer electrolyte fuel cells[J].Science,2009,324:71.
16 Peng H,Hou S,Dang D,et al.Ultra-high-performance doped carbon catalyst derived from o-phenylenediamine and the probable roles of Fe and melamine[J].Applied Catalysis B:Environmental,2014,158:60.
17 Wu G,Johnston C M,Mack N H,et al.Synthesis-structureperformance correlation for polyaniline-Me-C non-precious metal cathode catalysts for oxygen reduction in fuel cells[J].Journal of Materials Chemistry,2011,21:11392.
18 Wu G,More K L,Johnston C M,et al.High-performance electrocatalysts for oxygen reduction derived from polyaniline,iron,and cobalt[J].Science,2011,332:443.
19 殷敬华,莫志深.现代高分子物理学[M].北京:科学出版社,2001.
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21 Lu Min.Properties and applications of polyaniline[J].Journal of Functional Materials,1998(4):353(in Chinese).陆珉.导电聚苯胺(PAn)的特性及应用[J].功能材料,1998(4):353.
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23 Faubert G,C8téR,Guay D,et al.Activation and characterization of Fe-based catalysts for the reduction of oxygen in polymer electrolyte fuel cells[J].Electrochimica Acta,1998,43(14-15):1969.
24 Casanovas J,Ricart J M,Rubio J,et al.Origin of the large N 1s binding energy in X-ray photoelectron spectra of calcined carbonaceous materials[J].Journal of the American Chemical Society,1996,118(34):8071.
25 Wagner C D,Riggs W W,Davis L E,et al.Handbook of X-ray photoelectron spectroscopy[M].USA:Perkin-Elmer corporation Physical Electronics Division,1979:219.
26 Cochet M,Maser W K,Benito AM,et al.Synthesis of a new polyaniline/nanotube composite:“In-situ”polymerisation and charge transfer through site-selective interaction[J].Chemical Communications,2001,16:1450.
27 Tuinstra F,Koenig J L.Raman spectrum of graphite[J].The Journal of Chemical Physics,1970,53(3):1126.