在硫基功能化碳纳米管上组装壳层厚度可控的Au@Pt核壳纳米粒子以获得高的甲醇电催化氧化活性
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摘要
本工作致力于研究核壳结构Au@Pt纳米粒子(Au@Pt NPs)在多壁碳纳米管(MWCNTs)上的组装,试图获得高的甲醇电催化氧化活性。利用光化学晶种生长法合成了Au@Pt NPs,并通过改变Au与Pt的原子比来控制壳层(Pt层)的厚度,然后将不同壳层厚度的Au@Pt NPs组装到巯基(-SH)功能化的MWCNTs上,获得了一系列Au@Pt/MWCNTs复合物。应用透射电子显微镜(TEM)和X射线光电子能谱(XPS)研究了Au@Pt NPs和Au@Pt/MWCNTs复合物的形貌结构、表面化学组成和化学价态,并结合电化学方法研究了Au@Pt NPs的Pt壳层厚度对其组装效果的影响,以及测试了Au@Pt/MWCNTs催化剂对甲醇的电催化氧化的活性。结果表明,Au@Pt NPs通过其表面的Au或Pt与MWCNTs上的-SH形成共价键,从而实现Au@Pt NPs在MWCNTs上的组装。Pt壳层厚度对Au@Pt NPs在MWCNTs上组装的影响较大:当Pt壳层没有完全包裹Au核时,Au@Pt NPs表面暴露的Au促进了Au@Pt NPs在MWCNTs上的组装;而当Pt壳层完全包裹Au核时,Au@Pt NPs表面呈氧化态的Pt(Ⅱ)则对核壳纳米粒子的组装不利。Au、Pt原子比例为1∶1时,Au@Pt NPs能均匀地组装在MWCNTs上,且Au@Pt/MWCNTs(1∶1)催化剂对甲醇的电催化氧化具有较高的活性和稳定性。
It is the aim of this work to explore the assembly of Au@Pt core-shell nanoparticles(Au@Pt NPs)on multi-walled carbon nanotubes(MWCNTs)surfaces,attempting to acquire high activity for electrocatalytic methanol oxidation.We synthesized Au@Pt NPs whose shell(Pt layer)thickness can be varied by changing the molar ratio of Au/Pt,and then assembled these Au@PtNPs onto thiol(-SH)-functionalized MWCNTs surfaces to form a series of Au@Pt/MWCNTs composites.The surface chemical state,structure,and morphology of the Au@Pt NPs and Au@Pt/MWCNTs composites were characterized by transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS).The electrochemical tests including cyclic voltammetry(CV)and chronoamperometry(CA)were conducted to determine the assembly quality of Au@Pt NPs differing in shell thickness,and to characterize the activity of Au@Pt/MWCNTs catalysts.The results confirmed the successful assembly of Au@Pt NPs on MWCNTs surfaces via the covalent Pt-S/Au-S bonds formed between the monometallic Au or Pt of Au@Pt NPs and the thiol group of MWCNTs.The dispersion of Au@Pt NPs on MWCNTs highly depends on the atom ratios of Au/Pt.When the Pt envelopes outside the Au cores are incomplete,the exposed Au atoms facilitate the assembly of Au@Pt NPs.And on the contrary,if the Au cores are entirely coated by the Pt shell,the oxidation state Pt(Ⅱ)on the Au@Pt NPs surfaces will exert a negative effect.In particular,an 1∶1 atomic ratio of Au/Pt can result in the satisfactory dispersion of Au@Pt NPs on MWCNTs,also a distinctly higher activity and better stability of Au@Pt/MWCNTs(1∶1)compared with Pt/MWCNTs toward electrocatalytic methanol oxidation in alkaline media.
It is the aim of this work to explore the assembly of Au@Pt core-shell nanoparticles(Au@Pt NPs)on multi-walled carbon nanotubes(MWCNTs)surfaces,attempting to acquire high activity for electrocatalytic methanol oxidation.We synthesized Au@Pt NPs whose shell(Pt layer)thickness can be varied by changing the molar ratio of Au/Pt,and then assembled these Au@PtNPs onto thiol(-SH)-functionalized MWCNTs surfaces to form a series of Au@Pt/MWCNTs composites.The surface chemical state,structure,and morphology of the Au@Pt NPs and Au@Pt/MWCNTs composites were characterized by transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS).The electrochemical tests including cyclic voltammetry(CV)and chronoamperometry(CA)were conducted to determine the assembly quality of Au@Pt NPs differing in shell thickness,and to characterize the activity of Au@Pt/MWCNTs catalysts.The results confirmed the successful assembly of Au@Pt NPs on MWCNTs surfaces via the covalent Pt-S/Au-S bonds formed between the monometallic Au or Pt of Au@Pt NPs and the thiol group of MWCNTs.The dispersion of Au@Pt NPs on MWCNTs highly depends on the atom ratios of Au/Pt.When the Pt envelopes outside the Au cores are incomplete,the exposed Au atoms facilitate the assembly of Au@Pt NPs.And on the contrary,if the Au cores are entirely coated by the Pt shell,the oxidation state Pt(Ⅱ)on the Au@Pt NPs surfaces will exert a negative effect.In particular,an 1∶1 atomic ratio of Au/Pt can result in the satisfactory dispersion of Au@Pt NPs on MWCNTs,also a distinctly higher activity and better stability of Au@Pt/MWCNTs(1∶1)compared with Pt/MWCNTs toward electrocatalytic methanol oxidation in alkaline media.
引文
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6 Wang G,Huang B,Xiao L,et al.Pt skin on AuCu intermetallic substrate:A strategy to maximize Pt utilization for fuel cells[J].Journal of the American Chemical Society,2014,136:9643.
7 Liu B,Liao S,Liang Z.Core-shell structure:The best way to achieve low-Pt fuel cell electrocatalysts[J].Progress in Chemistry,2011(5):852(in Chinese).刘宾,廖世军,梁振兴.核壳结构:燃料电池中实现低铂电催化剂的最佳途径[J].化学进展,2011(5):852.
8 Li X,Liu J,He W,et al.Influence of the composition of core-shell Au-Pt nanoparticle electrocatalysts for the oxygen reduction reaction[J].Journal of Colloid and Interface Science,2010,344:132.
9 Sneed B T,Young A P,Jalalpoor D,et al.Shaped Pd-Ni-Pt coresandwich-shell nanoparticles:Influence of Ni sandwich layers on catalytic electrooxidations[J].ACS Nano,2014,8(7):7239.
10 Zhang L,Roling L T,Wang X,et al.Platinum-based nanocages with subnanometer-thick walls and well-defined,controllable facets[J].Science,2015,349(6246):412.
11 Sun P,Wei Q,Zhang Y,et al.Core-shell structured catalysts with platinum skin for fuel cells:The state-of-art methodological advances in fabrication and nanostructure control[J].Materials Review A:Review Papers,2018,32(5):1427(in Chinese).孙培川,魏清茂,张宇振,等.核壳型铂基燃料电池催化剂制备方法与微结构控制综述[J].材料导报:综述篇,2018,32(5):1427.
12 Mallik K,Mandal M,Pradhan N,et al.Seed mediated formation of bimetallic nanoparticles by UV irradiation:A photochemical approach for the preparation of“Core-Shell”type structures[J].Nano Letters,2001,6(1):319.
13 Lee Y W,Kim M,Kim Z H,et al.One-step synthesis of Au@Pd core-shell nanooctahedron[J].Journal of the American Chemical Society,2009,131:17036.
14 Wang S,Kristian N,Jiang S,et al.Controlled deposition of Pt on Au nanorods and their catalytic activity towards formic acid oxidation[J].Electrochemistry Communications,2008,10:961.
15 Zhao D,Xu B.Enhancement of Pt utilization in electrocatalysts by using gold nanoparticles[J].Angewandte Chemie International Edition,2006,118:5077.
16 Xu Y,Dong Y,Shi J,et al.Au@Pt core-shell nanoparticles supported on multiwalled carbon nanotubes for methanol oxidation[J].Catalysis Communications,2011,13:54.
17 Raoof J,Ojani R,Rashid-Nadimi S,et al.Electrochemical synthesis of bimetallic Au@Pt nanoparticles supported on gold film electrode by means of self-assembled monolayer[J].Journal of Electroanalytical Chemistry,2010,641:71.
18 Kumar S,Zou S.Electrooxidation of CO on uniform arrays of Au nanoparticles:Effects of particle size and interparticle spacing[J].Langmuir,2009,25(1):574.
19 Li W,Xie S,Qian L,et al.Large-scale synthesis of aligned carbon nanotubes[J].Science,1996,274:1701.
20 Zhao Y,Yang X,Tian J,et al.Methanol electro-oxidation on Ni@Pd core-shell nanoparticles supported on multi-walled carbon nanotubes in alkaline media[J].International Journal of Hydrogen Energy,2010,35:3249.
21 Zhang S,Qing M,Zhang H,et al.Electrocatalytic oxidation of formic acid on functional MWCNTs supported nanostructured Pd-Au catalyst[J].Electrochemistry Communications,2009,11:2249.
22 Yang G,Gao G,Zhao G,et al.Effective adhesion of Pt nanoparticles on thiolated multi-walled carbon nanotubes and their use for fabricating electrocatalysts[J].Carbon,2007,45:3036.
23 Yang D,Hennequin B,Sacher E.XPS demonstration ofπ-πinteraction between benzyl mercaptan and multiwalled carbon nanotubes and their use in the adhesion of Pt Nanoparticles[J].Chemistry of Materials,2006,18(21):5033.
24 Sainsbury T,Stolarczyk J,Fitzmaurice D.An experimental and theoretical study of the self-assembly of gold nanoparticles at the surface of functionalized multiwalled carbon nanotubes[J].The Journal of Physical Chemistry B,2005,109(34):16310.
25 Jin Y,Shen Y,Dong S.Electrochemical design of ultrathin platinum-coated gold nanoparticle monolayer films as a novel nanostructured electrocatalyst for oxygen reduction[J].The Journal of Physical Chemistry B,2004,108(24):8142.
26 Deivaraj T,Chen,W,Lee J Y.Preparation of PtNi nanoparticles for the electrocatalytic oxidation of methanol[J].Journal of Materials Chemistry,2003,13:2555.
27 Oezaslan M,Hasche F,Strasse P.PtCu3,PtCu and Pt3Cu alloy nanoparticle electrocatalysts for oxygen reduction reaction in alkaline and acidic media[J].Journal of the Electrochemical Society,2012,159(4):444.
28 Oezaslan M,Hasche F,Strasse P.Oxygen electroreduction on PtCo3,PtCo and Pt3Co alloy nanoparticles for alkaline and acidic PEM fuel cells[J].Journal of the Electrochemical Society,2012,159(4):394.
29 Xiong L,Yang X,Xu M,et al.Pt-Ni alloy nanoparticles supported on multiwalled carbon nanotubes for methanol oxidation in alkaline media[J].Journal of Solid State Electrochemistry,2013,17:805.
30 Duong H,Rigsby M,Zhou W,et al.Oxygen reduction catalysis of the Pt3Co alloy in alkaline and acidic media studied by X-ray photoelectron spectroscopy and electrochemical methods[J].The Journal of Physical Chemistry C,2007,111(36):13460.
2 Ali S,Ahmed R,Sohail M,et al.Co@Pt core-shell nanoparticles supported on carbon nanotubes as promising catalyst for methanol electro-oxidation[J].Journal of Industrial&Engineering Chemistry,2015,28:344
3 Park I S,Lee K S,Cho Y H,et al.Methanol electro-oxidation on carbon-supported and Pt-modified Au nanoparticles[J].Catalysis Today,2008,132:127.
4 Yang L,Yang W,Cai Q,et al.Well-dispersed PtAu nanoparticles loaded into anodic titania nanotubes:A high antipoison and stable catalyst systemfor methanol oxidation in alkaline media[J].Journal of Physical Chemistry C,2007,111(44):16613.
5 Wang J,Yin G,Liu H,et al.Carbon nanotubes supported Pt-Au catalysts for methanol-tolerant oxygen reduction reaction:A comparison between Pt/Au and PtAu nanoparticles[J].Journal of Power Sources,2009,194:668.
6 Wang G,Huang B,Xiao L,et al.Pt skin on AuCu intermetallic substrate:A strategy to maximize Pt utilization for fuel cells[J].Journal of the American Chemical Society,2014,136:9643.
7 Liu B,Liao S,Liang Z.Core-shell structure:The best way to achieve low-Pt fuel cell electrocatalysts[J].Progress in Chemistry,2011(5):852(in Chinese).刘宾,廖世军,梁振兴.核壳结构:燃料电池中实现低铂电催化剂的最佳途径[J].化学进展,2011(5):852.
8 Li X,Liu J,He W,et al.Influence of the composition of core-shell Au-Pt nanoparticle electrocatalysts for the oxygen reduction reaction[J].Journal of Colloid and Interface Science,2010,344:132.
9 Sneed B T,Young A P,Jalalpoor D,et al.Shaped Pd-Ni-Pt coresandwich-shell nanoparticles:Influence of Ni sandwich layers on catalytic electrooxidations[J].ACS Nano,2014,8(7):7239.
10 Zhang L,Roling L T,Wang X,et al.Platinum-based nanocages with subnanometer-thick walls and well-defined,controllable facets[J].Science,2015,349(6246):412.
11 Sun P,Wei Q,Zhang Y,et al.Core-shell structured catalysts with platinum skin for fuel cells:The state-of-art methodological advances in fabrication and nanostructure control[J].Materials Review A:Review Papers,2018,32(5):1427(in Chinese).孙培川,魏清茂,张宇振,等.核壳型铂基燃料电池催化剂制备方法与微结构控制综述[J].材料导报:综述篇,2018,32(5):1427.
12 Mallik K,Mandal M,Pradhan N,et al.Seed mediated formation of bimetallic nanoparticles by UV irradiation:A photochemical approach for the preparation of“Core-Shell”type structures[J].Nano Letters,2001,6(1):319.
13 Lee Y W,Kim M,Kim Z H,et al.One-step synthesis of Au@Pd core-shell nanooctahedron[J].Journal of the American Chemical Society,2009,131:17036.
14 Wang S,Kristian N,Jiang S,et al.Controlled deposition of Pt on Au nanorods and their catalytic activity towards formic acid oxidation[J].Electrochemistry Communications,2008,10:961.
15 Zhao D,Xu B.Enhancement of Pt utilization in electrocatalysts by using gold nanoparticles[J].Angewandte Chemie International Edition,2006,118:5077.
16 Xu Y,Dong Y,Shi J,et al.Au@Pt core-shell nanoparticles supported on multiwalled carbon nanotubes for methanol oxidation[J].Catalysis Communications,2011,13:54.
17 Raoof J,Ojani R,Rashid-Nadimi S,et al.Electrochemical synthesis of bimetallic Au@Pt nanoparticles supported on gold film electrode by means of self-assembled monolayer[J].Journal of Electroanalytical Chemistry,2010,641:71.
18 Kumar S,Zou S.Electrooxidation of CO on uniform arrays of Au nanoparticles:Effects of particle size and interparticle spacing[J].Langmuir,2009,25(1):574.
19 Li W,Xie S,Qian L,et al.Large-scale synthesis of aligned carbon nanotubes[J].Science,1996,274:1701.
20 Zhao Y,Yang X,Tian J,et al.Methanol electro-oxidation on Ni@Pd core-shell nanoparticles supported on multi-walled carbon nanotubes in alkaline media[J].International Journal of Hydrogen Energy,2010,35:3249.
21 Zhang S,Qing M,Zhang H,et al.Electrocatalytic oxidation of formic acid on functional MWCNTs supported nanostructured Pd-Au catalyst[J].Electrochemistry Communications,2009,11:2249.
22 Yang G,Gao G,Zhao G,et al.Effective adhesion of Pt nanoparticles on thiolated multi-walled carbon nanotubes and their use for fabricating electrocatalysts[J].Carbon,2007,45:3036.
23 Yang D,Hennequin B,Sacher E.XPS demonstration ofπ-πinteraction between benzyl mercaptan and multiwalled carbon nanotubes and their use in the adhesion of Pt Nanoparticles[J].Chemistry of Materials,2006,18(21):5033.
24 Sainsbury T,Stolarczyk J,Fitzmaurice D.An experimental and theoretical study of the self-assembly of gold nanoparticles at the surface of functionalized multiwalled carbon nanotubes[J].The Journal of Physical Chemistry B,2005,109(34):16310.
25 Jin Y,Shen Y,Dong S.Electrochemical design of ultrathin platinum-coated gold nanoparticle monolayer films as a novel nanostructured electrocatalyst for oxygen reduction[J].The Journal of Physical Chemistry B,2004,108(24):8142.
26 Deivaraj T,Chen,W,Lee J Y.Preparation of PtNi nanoparticles for the electrocatalytic oxidation of methanol[J].Journal of Materials Chemistry,2003,13:2555.
27 Oezaslan M,Hasche F,Strasse P.PtCu3,PtCu and Pt3Cu alloy nanoparticle electrocatalysts for oxygen reduction reaction in alkaline and acidic media[J].Journal of the Electrochemical Society,2012,159(4):444.
28 Oezaslan M,Hasche F,Strasse P.Oxygen electroreduction on PtCo3,PtCo and Pt3Co alloy nanoparticles for alkaline and acidic PEM fuel cells[J].Journal of the Electrochemical Society,2012,159(4):394.
29 Xiong L,Yang X,Xu M,et al.Pt-Ni alloy nanoparticles supported on multiwalled carbon nanotubes for methanol oxidation in alkaline media[J].Journal of Solid State Electrochemistry,2013,17:805.
30 Duong H,Rigsby M,Zhou W,et al.Oxygen reduction catalysis of the Pt3Co alloy in alkaline and acidic media studied by X-ray photoelectron spectroscopy and electrochemical methods[J].The Journal of Physical Chemistry C,2007,111(36):13460.