The commercialization of proton exchange membrane fuel cells(PEMFCs)could provide a cleaner energy society in the near future.However,the sluggish reaction kinetics and harsh conditions of the oxygen reduction reactio...The commercialization of proton exchange membrane fuel cells(PEMFCs)could provide a cleaner energy society in the near future.However,the sluggish reaction kinetics and harsh conditions of the oxygen reduction reaction affect the durability and cost of PEMFCs.Most previous reports on Pt-based electrocatalyst designs have focused more on improving their activity;however,with the commercialization of PEMFCs,durability has received increasing attention.In-depth insight into the structural evolution of Pt-based electrocatalysts throughout their lifecycle can contribute to further optimization of their activity and durability.The development of in situ electron microscopy and other in situ techniques has promoted the elucidation of the evolution mechanism.This mini review highlights recent advances in the structural evolution of Pt-based electrocatalysts.The mechanisms are adequately discussed,and some methods to inhibit or exploit the structural evolution of the catalysts are also briefly reviewed.展开更多
The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte...The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.展开更多
Carbon supported Pt（Pt/C） electrocatalysts were prepared with glucose as protection agent and NaBH 4 as reductant.The Pt nanoparticles deposited on carbon support presented reduced size and well dispersity attribute...Carbon supported Pt（Pt/C） electrocatalysts were prepared with glucose as protection agent and NaBH 4 as reductant.The Pt nanoparticles deposited on carbon support presented reduced size and well dispersity attributed to the protection effect of glucose.Glucose absorbed on the particle surface was readily removed by water washing without leading to agglomeration of the Pt nanoparticles.The as-prepared Pt/C electrocatalysts showed improved mass activity for methanol electrooxidation compared to the catalyst prepared without glucose protection.The improved performance is attributed to the larger electrochemical active surface area thus increased active sites on the Pt/C elctrocatalysts prepared under the protection of glucose.展开更多
Although carbon-supported platinum(Pt/C) is still considered the most active electrocatalyst for hydrogen evolution reaction(HER) and oxygen reduction reaction(ORR), its applications in metal–air batteries as a catho...Although carbon-supported platinum(Pt/C) is still considered the most active electrocatalyst for hydrogen evolution reaction(HER) and oxygen reduction reaction(ORR), its applications in metal–air batteries as a cathode catalyst, or for oxygen generation via water splitting electrolysis as an anode catalyst is mainly constrained by the insufficient kinetic activity and stability in the oxygen evolution reaction(OER). Here, MOF-253-derived nitrogen-doped carbon(N/C)-confined Pt single nanocrystals(Pt@N/C) have been synthesized and shown to be efficient catalysts for the OER. Even with low Pt mass loading of 6.1 wt%(Pt@N/C-10), the catalyst exhibits greatly improved activity and long-time stability as an efficient OER catalyst. Such high catalytic performance is attributed to the core-shell structure relationship, in which the active N-doped-C shell not only provides a protective shield to avoid rapid Pt nanocrystal oxidation at high potentials and inhibits the Pt migration and agglomeration, but also improves the conductivity and charge transfer kinetics.展开更多
Carbon supported Pt-Co alloys are among the most promising electrocatalysts towards oxygen reduction reaction(ORR)for the application in low temperature fuel cells and beyond,thus their facile and green synthesis is h...Carbon supported Pt-Co alloys are among the most promising electrocatalysts towards oxygen reduction reaction(ORR)for the application in low temperature fuel cells and beyond,thus their facile and green synthesis is highly demanded.Herein we initially report an alternate aqueous phase one-pot synthesis of such catalysts(containing nominally ca.20 wt.%Pt)based on dimethylamine borane(DMAB)reduction.The as-obtained electrocatalyst(denoted as Pt3Co/C-DMAB)is compared with the ones obtained by NaBH4 and N2H4·H2O reduction(denoted as Pt3Co/C-NaBH4 and Pt3Co/C-N2H4·H2O,respectively)as well as a commercial Pt/C,in terms of the structure and electrocatalytic property.It turns out that Pt3Co/C-DMAB exhibits the highest ORR performance among all the tested samples in an O2-saturated 0.1 mol/L HClO4,with the mass activity(specific activity)ca.4(6)times as large as that for Pt/C.After 10000 cycles of the accelerated degradation test,the half-wave potential for ORR on Pt3Co/C-DMAB decreases only by 4 mV,in contrast to 24 mV for that on Pt/C.Pt3Co/C-NaBH4 or Pt3Co/C-N2H4·H2O shows a specific activity comparable to that for Pt3Co/C-DMAB,but a mass activity similar to that for Pt/C.ICP-AES,TEM,XRD and XPS characterizations indicate that Pt3Co nanoparticles are well-dispersed and alloyed with a mean particle size of ca.3.4±0.4 nm,contributing to the prominent electrocatalytic performance of Pt3Co/C-DMAB.This simple aqueous synthetic route may provide an alternate opportunity for developing efficient practical electrocatalysts for ORR.展开更多
Highly-dispersed platinum and platinum-based catalysts on a conductive support are commonly used as electrode materials in low-temperature fuel cells, particularly the hydrogen PEMFC and the direct methanol PEMFC. The...Highly-dispersed platinum and platinum-based catalysts on a conductive support are commonly used as electrode materials in low-temperature fuel cells, particularly the hydrogen PEMFC and the direct methanol PEMFC. The performance and durability/stability of these catalysts strongly depend on the characteristics of the support. Catalysts supported on high surface area carbon black are widely used in low-temperature fuel cells. However, the corrosion of carbon black has been recognized as one of major causes of performance degradation and durability issues of low-temperature fuel cells under high-potential conditions. So the need for alternative supports with outstanding physical and mechanical properties to carry out the successful reaction in catalyst layer and give a longer lifetime for the electrocatalysts is inevitable. The emergence of nanotechnology and development of nanostructure materials in recent years has opened up new avenues of materials development for low-temperature fuel cells. This paper presents the performance with a variety of carbon-based nanostructured materials such as carbon nanotubes (CNT), carbon nanofibers (CNF), carbon aerogels, nanoplates of graphene, etc. So the present paper provides an overview of these nanostructured materials as low-temperature fuel cell catalyst supports. The improved characteristics of the nanostructured supports with respect to commercially used carbon black (Vulcan XC-72) and their effect on the electrochemical activity are highlighted. Additionally, it reviews the literature on the synthesis of nanostructured-supported Pt electrocatalysts for proton exchange membrane (PEM) fuel cell catalyst loading reducing through the improvement of catalyst utilization and activity. The features of each synthetic method were also discussed based on the morphology of the synthesized catalysts.展开更多
文摘The commercialization of proton exchange membrane fuel cells(PEMFCs)could provide a cleaner energy society in the near future.However,the sluggish reaction kinetics and harsh conditions of the oxygen reduction reaction affect the durability and cost of PEMFCs.Most previous reports on Pt-based electrocatalyst designs have focused more on improving their activity;however,with the commercialization of PEMFCs,durability has received increasing attention.In-depth insight into the structural evolution of Pt-based electrocatalysts throughout their lifecycle can contribute to further optimization of their activity and durability.The development of in situ electron microscopy and other in situ techniques has promoted the elucidation of the evolution mechanism.This mini review highlights recent advances in the structural evolution of Pt-based electrocatalysts.The mechanisms are adequately discussed,and some methods to inhibit or exploit the structural evolution of the catalysts are also briefly reviewed.
基金The project was supported by the FAPESP(2014/09087-4,2014/50279-4).
文摘The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.
基金Supported by the National Innovative Research Program for Undergraduates,China(No.2010A33039)the Science and Technology Development Program of Jilin Province,China(No.20100420)
文摘Carbon supported Pt（Pt/C） electrocatalysts were prepared with glucose as protection agent and NaBH 4 as reductant.The Pt nanoparticles deposited on carbon support presented reduced size and well dispersity attributed to the protection effect of glucose.Glucose absorbed on the particle surface was readily removed by water washing without leading to agglomeration of the Pt nanoparticles.The as-prepared Pt/C electrocatalysts showed improved mass activity for methanol electrooxidation compared to the catalyst prepared without glucose protection.The improved performance is attributed to the larger electrochemical active surface area thus increased active sites on the Pt/C elctrocatalysts prepared under the protection of glucose.
文摘Although carbon-supported platinum(Pt/C) is still considered the most active electrocatalyst for hydrogen evolution reaction(HER) and oxygen reduction reaction(ORR), its applications in metal–air batteries as a cathode catalyst, or for oxygen generation via water splitting electrolysis as an anode catalyst is mainly constrained by the insufficient kinetic activity and stability in the oxygen evolution reaction(OER). Here, MOF-253-derived nitrogen-doped carbon(N/C)-confined Pt single nanocrystals(Pt@N/C) have been synthesized and shown to be efficient catalysts for the OER. Even with low Pt mass loading of 6.1 wt%(Pt@N/C-10), the catalyst exhibits greatly improved activity and long-time stability as an efficient OER catalyst. Such high catalytic performance is attributed to the core-shell structure relationship, in which the active N-doped-C shell not only provides a protective shield to avoid rapid Pt nanocrystal oxidation at high potentials and inhibits the Pt migration and agglomeration, but also improves the conductivity and charge transfer kinetics.
基金supported by the National Basic Research Program of China(973 Program,2015CB932303)the National Natural Science Foundation of China(NSFC)(21733004 and 21473039)the International Cooperation Program of Shanghai Science and Technology Committee(STCSM)(17520711200)~~
文摘Carbon supported Pt-Co alloys are among the most promising electrocatalysts towards oxygen reduction reaction(ORR)for the application in low temperature fuel cells and beyond,thus their facile and green synthesis is highly demanded.Herein we initially report an alternate aqueous phase one-pot synthesis of such catalysts(containing nominally ca.20 wt.%Pt)based on dimethylamine borane(DMAB)reduction.The as-obtained electrocatalyst(denoted as Pt3Co/C-DMAB)is compared with the ones obtained by NaBH4 and N2H4·H2O reduction(denoted as Pt3Co/C-NaBH4 and Pt3Co/C-N2H4·H2O,respectively)as well as a commercial Pt/C,in terms of the structure and electrocatalytic property.It turns out that Pt3Co/C-DMAB exhibits the highest ORR performance among all the tested samples in an O2-saturated 0.1 mol/L HClO4,with the mass activity(specific activity)ca.4(6)times as large as that for Pt/C.After 10000 cycles of the accelerated degradation test,the half-wave potential for ORR on Pt3Co/C-DMAB decreases only by 4 mV,in contrast to 24 mV for that on Pt/C.Pt3Co/C-NaBH4 or Pt3Co/C-N2H4·H2O shows a specific activity comparable to that for Pt3Co/C-DMAB,but a mass activity similar to that for Pt/C.ICP-AES,TEM,XRD and XPS characterizations indicate that Pt3Co nanoparticles are well-dispersed and alloyed with a mean particle size of ca.3.4±0.4 nm,contributing to the prominent electrocatalytic performance of Pt3Co/C-DMAB.This simple aqueous synthetic route may provide an alternate opportunity for developing efficient practical electrocatalysts for ORR.
文摘Highly-dispersed platinum and platinum-based catalysts on a conductive support are commonly used as electrode materials in low-temperature fuel cells, particularly the hydrogen PEMFC and the direct methanol PEMFC. The performance and durability/stability of these catalysts strongly depend on the characteristics of the support. Catalysts supported on high surface area carbon black are widely used in low-temperature fuel cells. However, the corrosion of carbon black has been recognized as one of major causes of performance degradation and durability issues of low-temperature fuel cells under high-potential conditions. So the need for alternative supports with outstanding physical and mechanical properties to carry out the successful reaction in catalyst layer and give a longer lifetime for the electrocatalysts is inevitable. The emergence of nanotechnology and development of nanostructure materials in recent years has opened up new avenues of materials development for low-temperature fuel cells. This paper presents the performance with a variety of carbon-based nanostructured materials such as carbon nanotubes (CNT), carbon nanofibers (CNF), carbon aerogels, nanoplates of graphene, etc. So the present paper provides an overview of these nanostructured materials as low-temperature fuel cell catalyst supports. The improved characteristics of the nanostructured supports with respect to commercially used carbon black (Vulcan XC-72) and their effect on the electrochemical activity are highlighted. Additionally, it reviews the literature on the synthesis of nanostructured-supported Pt electrocatalysts for proton exchange membrane (PEM) fuel cell catalyst loading reducing through the improvement of catalyst utilization and activity. The features of each synthetic method were also discussed based on the morphology of the synthesized catalysts.
文摘质子交换膜燃料电池(PEMFCs)因其高能量密度、低操作温度和环保等特性,被视为极具潜力的能量转换系统.目前,碳载铂颗粒(Pt/C)是PEMFCs阴极氧还原反应(ORR)中使用最广泛的催化剂.然而,Pt与碳载体间的电子结构差异导致Pt纳米颗粒(Pt NPs)易从碳载体上脱落,严重降低了ORR的催化活性.此外,Pt的高成本和稀缺性也限制了其广泛应用.相比之下,Pt纳米枝晶(NDs)因具有高利用率的表面活性位点而备受关注.然而,Pt NDs的合成通常需要严格控制反应条件,且其与碳基底间的弱相互作用易导致活性位点损失和性能下降.因此,开发具有强金属载体相互作用的Pt复合碳催化剂对PEMFCs的实际应用至关重要.本文通过原位Cl-介导的生长策略,结合碳本征空位工程,成功制备了分散在富含碳本征空位的中空氮掺杂碳基底上的Pt NDs催化剂(Pt@HNC-V-800).拉曼光谱和电子顺磁共振光谱结果表明,碳本征空位的形成机制源于碳基底结构中氮原子的耗散,该过程引起碳原子的重新排列,进而产生了丰富的本征缺陷位点.X射线吸收光谱和X射线光电子能谱结果表明,与无碳空位的Pt@HNC催化剂相比,富含本征碳空位的样品(Pt@HNC-V-800)表现出较低的Pt-Pt键配位数(8.64)和更强的给电子效应.得益于Pt NDs丰富的活性位点及其与本征碳空位基底之间的强电子效应,Pt@HNC-V-800的ORR半波电位高达0.947 V,质量活性和比表面活性分别为1.55 A mg^(-1) Pt和1.85 mA cm^(-2),是商用Pt/C的8.2和6.8倍(0.191 A mg^(-1)Pt和0.27 mA cm^(-2)).加速耐久性测试结果表明,经20000次电势循环后,Pt@HNC-V-800的活性无明显变化,其活性损失远低于无碳本征空位的Pt@HNC材料和商业Pt/C催化剂.因此,与无碳本征空位的Pt@HNC材料相比,Pt@HNC-V-800的ORR活性和稳定性都有较大提升,进一步证实了碳本征空位工程协同Pt NDs策略的优越性.此外,密度泛函理论计算结果表明,Pt@HNC-V的丰富空位降低了氧中间体过电势,优化了ORR中间体在Pt NDs上的吸附能,进而提高了催化剂的ORR本征活性.同时,富碳本征空位的存在增强了Pt NDs在碳载体上的结合能,使Pt NDs不易在电势循环过程中脱离碳载体,从而增强了稳定性.综上所述,本文通过Pt NDs与碳本征空位工程协同效应策略,精准调控碳负载Pt基催化剂的结构,大幅提升其在酸性条件下的ORR性能,为进一步设计高性能的ORR电催化剂提供了新思路.
