Mesoporous metals have shown considerable promise in the field of electrocatalysis due to their intrinsic properties[1,2].On one hand,high porosity offers a larger surface area than solid nanoparticles,significantly e...Mesoporous metals have shown considerable promise in the field of electrocatalysis due to their intrinsic properties[1,2].On one hand,high porosity offers a larger surface area than solid nanoparticles,significantly enhancing the utilization efficiency of precious metals[3-5].On the other hand,the continuous crystalline framework facilitates rapid electron and mass transfer while inhibiting Ostwald ripening,thereby significantly enhancing electrocatalytic activity and stability[2].More importantly,nanopores create a confined,enzyme-like microenvironment that modulates local electronic states and reaction conditions,steering catalytic selectivity[6].Despite their great potential,the application of mesoporous metals,especially through precise modulation of electronic structure to achieve single-product selectivity in complex electrocatalytic reactions,remains limited.展开更多
Although many previous studies have show n that the shape-c ontrol of nano crystal(NCs)is an efficient strategy to improve the catalytic performance,these syntheses were conducted under very different conditions,which...Although many previous studies have show n that the shape-c ontrol of nano crystal(NCs)is an efficient strategy to improve the catalytic performance,these syntheses were conducted under very different conditions,which are not suitable for the shape-dependent properties studies as well as catalysis optimization.Herein,we demonstrate an effective method for the selective synthesis of well-defined PtPb NCs in a highly con trollable mariner.Four disti net PtPb NCs,n amely PtPb pea nut nano crystals,PtPb hexag onal nan opiates,PtPb octahedra nano crystals(ONCs)and PtPb nan oparticles have been selectively prepared in the prese nee of differe nt phe nols.Sign ifica ntly,we found that the created PtPb NCs/C shows the shape-dependent activity with the optimized PtPb ONCs/C being the most active for the ethanol reforming to H2,22.4 times higher than the commercial Pt/C.The high performance of PtPb ONCs/C has been also successfully expanded into other polyhydric alcohols reformings.X-ray photoelectron spectroscopy(XPS)reveals that the high Pt(O)/Pt(ll)ratio in PtPb NCs/C enhances the alcohols reforming.The density functional theory(DFT)studies show the PtPb ONCs possess the highest surface averaged electronic occu patio n for unit Pt-atom,matchi ng well with XPS results.The PtPb ONCs/C also displays excelle nt durability with limited activity decay and negligible structure/composition changes after ten cycles.This work demonstrates an important advance in the high-level control of metallic nanostructures to tune the catalytic activities.展开更多
鉴于封闭式挤压油膜阻尼器(Hermetically sealed squeeze film damper,HSFD)良好的阻尼性能,并联HSFD的多孔质可倾瓦轴承(Porous tilting pad bearing,PTPBs)有望用于兆瓦级涡轮机械,具有广泛的应用前景。呈现了一种HSFD等效刚度和等效...鉴于封闭式挤压油膜阻尼器(Hermetically sealed squeeze film damper,HSFD)良好的阻尼性能,并联HSFD的多孔质可倾瓦轴承(Porous tilting pad bearing,PTPBs)有望用于兆瓦级涡轮机械,具有广泛的应用前景。呈现了一种HSFD等效刚度和等效阻尼的计算方法,该方法成功体现了阻尼器刚度和阻尼的“频率依赖”特性。将HSFD与多孔质瓦块模型耦合建立了该轴承的综合理论模型,并进一步验证了该模型的正确性。最后研究了供气压力、轴承间隙以及是否安装HSFD等对轴承静动态特性的影响。结果表明,HSFD的存在大幅提高了轴承的阻尼水平和稳定性。展开更多
文摘Mesoporous metals have shown considerable promise in the field of electrocatalysis due to their intrinsic properties[1,2].On one hand,high porosity offers a larger surface area than solid nanoparticles,significantly enhancing the utilization efficiency of precious metals[3-5].On the other hand,the continuous crystalline framework facilitates rapid electron and mass transfer while inhibiting Ostwald ripening,thereby significantly enhancing electrocatalytic activity and stability[2].More importantly,nanopores create a confined,enzyme-like microenvironment that modulates local electronic states and reaction conditions,steering catalytic selectivity[6].Despite their great potential,the application of mesoporous metals,especially through precise modulation of electronic structure to achieve single-product selectivity in complex electrocatalytic reactions,remains limited.
基金This work was financially supported by the National Key Technology R&D Program of China(Nos.2016YFA0204100 and 2017YFA0208200)the National Natural Science Foundation of China(No.21571135)+2 种基金Young Thousand Talented Program,the Natural Science Foundation of Jiangsu Higher Education Institutions(No.17KJB150032)the project of scientific and technologic infrastructure of Suzhou(No.SZS201708)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),and the start-up supports from Soochow University.
文摘Although many previous studies have show n that the shape-c ontrol of nano crystal(NCs)is an efficient strategy to improve the catalytic performance,these syntheses were conducted under very different conditions,which are not suitable for the shape-dependent properties studies as well as catalysis optimization.Herein,we demonstrate an effective method for the selective synthesis of well-defined PtPb NCs in a highly con trollable mariner.Four disti net PtPb NCs,n amely PtPb pea nut nano crystals,PtPb hexag onal nan opiates,PtPb octahedra nano crystals(ONCs)and PtPb nan oparticles have been selectively prepared in the prese nee of differe nt phe nols.Sign ifica ntly,we found that the created PtPb NCs/C shows the shape-dependent activity with the optimized PtPb ONCs/C being the most active for the ethanol reforming to H2,22.4 times higher than the commercial Pt/C.The high performance of PtPb ONCs/C has been also successfully expanded into other polyhydric alcohols reformings.X-ray photoelectron spectroscopy(XPS)reveals that the high Pt(O)/Pt(ll)ratio in PtPb NCs/C enhances the alcohols reforming.The density functional theory(DFT)studies show the PtPb ONCs possess the highest surface averaged electronic occu patio n for unit Pt-atom,matchi ng well with XPS results.The PtPb ONCs/C also displays excelle nt durability with limited activity decay and negligible structure/composition changes after ten cycles.This work demonstrates an important advance in the high-level control of metallic nanostructures to tune the catalytic activities.
文摘鉴于封闭式挤压油膜阻尼器(Hermetically sealed squeeze film damper,HSFD)良好的阻尼性能,并联HSFD的多孔质可倾瓦轴承(Porous tilting pad bearing,PTPBs)有望用于兆瓦级涡轮机械,具有广泛的应用前景。呈现了一种HSFD等效刚度和等效阻尼的计算方法,该方法成功体现了阻尼器刚度和阻尼的“频率依赖”特性。将HSFD与多孔质瓦块模型耦合建立了该轴承的综合理论模型,并进一步验证了该模型的正确性。最后研究了供气压力、轴承间隙以及是否安装HSFD等对轴承静动态特性的影响。结果表明,HSFD的存在大幅提高了轴承的阻尼水平和稳定性。
