Based on the alloy Cu55Ni45 (at pct), holding the proportion of Cu to Ni in constant and in the temperature range of 1233~1573 K, the wetting angles of CuNi-0~56 at pct Ti alloys on Si3N4 have been measured by the ses...Based on the alloy Cu55Ni45 (at pct), holding the proportion of Cu to Ni in constant and in the temperature range of 1233~1573 K, the wetting angles of CuNi-0~56 at pct Ti alloys on Si3N4 have been measured by the sessile drop method. With the increase of Ti content, the wetting angles decreased. The equilibrium wetting angle was 5° when Ti content ≥32 at pct.In the case of same Ti content, the activity of Ti in CuNiTi alloy was weaker than that in CuTi alloy The cross-section of the CuNiTi-Si3N4 interface and the elements distribution were examined by scanning electron microscope with X-ray wave-dispersion spectrometer, and the reaction products formed at the interface were determined by X-ray diffiaction analysis method.展开更多
Sodium(Na)metal anode exhibits a potential candidate in next-generation rechargeable batteries owing to its advantages of high earth abundance and low cost.Unfortunately,the practical development of sodium metal batte...Sodium(Na)metal anode exhibits a potential candidate in next-generation rechargeable batteries owing to its advantages of high earth abundance and low cost.Unfortunately,the practical development of sodium metal batteries is inherently plagued by challenges such as the side reactions and the growth of Na dendrites.Herein we report a highly stable Bi-based“sodiophilic”substrate to stabilize Na anode,which is created by in-situ electrochemical reactions of 3D hierarchical porous Bi_(2)MoO_(6)(BMO)microspheres.BMO is initially transformed into the Bi“nanoseeds”embedded in the Na-Mo-O matrix.Subsequently,the Bi nanoseeds working as preferential nucleation sites through the formation of BiNa alloy enable the non-dendritic Na deposition.The asymmetric cells based on such BMO-based substrate can deliver a long-term cycling for 600 cycles at a large capacity of 4 m Ah cm^(-2) and for 800 cycles at a high current density of 10 m A cm^(-2).Even at a high depth of discharge(66.67%),the Na-predeposited BMO(Na@BMO)electrodes can cycle for more than 1600 h.The limited Na@BMO anodes coupled with the Na_(3)V_(2)(PO_(4))_(3) cathodes(N/P ratio of 3)in full cells also show excellent electrochemical performance with a capacity retention of about 97.4%after 1100 cycles at 2 C.展开更多
Tin (Sn) metal foil is a promising anode for next-generation high-energy–density lithium-ion batteries (LIBs) due to its high capacity and easy processibility. However, the pristine Sn foil anode suffers nonuniform a...Tin (Sn) metal foil is a promising anode for next-generation high-energy–density lithium-ion batteries (LIBs) due to its high capacity and easy processibility. However, the pristine Sn foil anode suffers nonuniform alloying/dealloying reaction with lithium (Li) and huge volume variation, leading to electrode pulverization and inferior electrochemical performance. Herein, we proposed that reduced grain size and elaborate porosity design of Sn foil can circumvent the nonuniform alloy reaction and buffer the volume change during the lithiation/delithiation cycling. Experimentally, we designed a three-dimensional interconnected porous Sn (3DIP-Sn) foil by a facile chemical alloying/dealloying approach, which showed improved electrochemical performance. The enhanced structure stability of the as-fabricated 3DIP-Sn foil was verified by chemo-mechanical simulations and experimental investigation. As expected, the 3DIP-Sn foil anode revealed a long cycle lifespan of 4400 h at 0.5 mA cm^(−2) and 1 mAh cm^(−2) in Sn||Li half cells. A 3DIP-Sn||LiFePO_(4) full cell with LiFePO_(4) loading of 7.1 mg cm^(−2) exhibited stable cycling for 500 cycles with 80% capacity retention at 70 mA g^(−1). Pairing with high-loading commercial LiNi0.6Co0.2Mn0.2O_(2) (NCM622, 18.4 mg cm^(−2)) cathode, a 3DIP-Sn||NCM622 full cell delivered a high reversible capacity of 3.2 mAh cm^(−2). These results demonstrated the important role of regulating the uniform alloying/dealloying reaction and circumventing the localized strain/stress in improving the electrochemical performance of Sn foil anodes for advanced LIBs.展开更多
Pouring temperature and time are the most important influencing factors on interfacial reaction during the centrifugal casting. When cast at high temperatures, the crucible becomes brittle and prone to cracking, and s...Pouring temperature and time are the most important influencing factors on interfacial reaction during the centrifugal casting. When cast at high temperatures, the crucible becomes brittle and prone to cracking, and shows a low stability. In this paper, we studied the centrifugal casting of Ti-47.5-Al-2.5V-1Cr alloy, and explored the effects of pouring temperature on the interfacial reaction. Castings at 1 600, 1 650, and 1 700 ℃ were obtained by controlling the other parameters constant in the experiments. The microstructure, elemental distribution, thickness of the reaction layer and phase composition of the castings at the interface were studied. The results show that the thickness at the interfacial reaction layer is increased by raising the pouring temperature. The elements in the mold and the matrix were double-diffused and reacted at the interface during the casting process, and formed solid solutions with the precipitation of many new phases such as AlOand TiO. The roughness of interface structure and layer thickness of reaction increase with the rise of temperature, and the interfacial reaction is more intense. There is a minimum layer thickness of the reaction layer that is 80 μm when the temperature is 1 600 ℃.展开更多
In this paper, TiAl alloy powders were prepared successfully by high-energy ball milling and diffusion reaction in vacuum at low temperature. The titanium powder, aluminum powder, and titanium hydride powder were used...In this paper, TiAl alloy powders were prepared successfully by high-energy ball milling and diffusion reaction in vacuum at low temperature. The titanium powder, aluminum powder, and titanium hydride powder were used as raw materials. The samples were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD), field-emission scanning electron microscopy(FESEM), and differential thermal analysis(DTA). The results show that the alloy powders with the main intermetallic compounds of TiAl are obtained using Ti-Al powders and TiH2-Al powders after heated for 2 h at 500 ℃,3 h at 600 ℃,and 3 h at 750 ℃,respectively.The average grain sizes of alloy powder are about 45 and20 μm with irregular shape, respectively. The prepared TiAl alloy powders are relatively pure, and the average quality content of oxygen in the alloy powders is0.33 wt%. The forming process of alloy powder contains both the diffusion reaction of Ti and Al,which gives priority to the diffusion reaction of aluminum.展开更多
Controlled syntheses of PtNi metal nanocrystals with unique structures for catalyzing oxygen reduction reactions (ORRs) have attracted great interest. Here, we report the one-step synthesis of single-crystal PtNi oc...Controlled syntheses of PtNi metal nanocrystals with unique structures for catalyzing oxygen reduction reactions (ORRs) have attracted great interest. Here, we report the one-step synthesis of single-crystal PtNi octahedra with in situ-developed highly concave features and self-confined composition that are optimal for ORR. Detailed studies revealed that the Pt-rich seeding, subsequent Pt/Ni co-reduction, and Pt-Ni interfusion resulted in uniform single-crystal PtNi octahedra, and that the combination of Ni facet segregation and oxygen etching of a Ni-rich surface led to the concavity and confined Ni content. The concave PtNi nanocrystals exhibited much higher ORR performance than the commercially available Pt/C catalyst in terms of both specific activity (29.1 times higher) and mass activity (12.9 times higher) at 0.9 V (vs. reversible hydrogen electrode (RHE)). The performance was also higher than that of PtNi octahedra without concavity, confirming that the higher activity was closely related to its morphology. Moreover, the concave octahedra also exhibited remarkable stability in ORR (93% mass activity remained after 10,000 cycles between 0.6 and 1.1 V vs. RHE) owing to the passivation of the unstable sites.展开更多
High performance methanol oxidation reaction (MOR) catalysts are critical to the performance of attractive, direct methanol fuel cells. Here, we use surface controlled PtNi alloy nanoparticles as model catalysts to ...High performance methanol oxidation reaction (MOR) catalysts are critical to the performance of attractive, direct methanol fuel cells. Here, we use surface controlled PtNi alloy nanoparticles as model catalysts to study the MOR mechanism and give further guidance to the design of new high performance MOR catalysts. The enhanced MOR activity of PtNi alloy was mainly attributed to the enhanced OH adsorption owing to surface Ni sites. This suggests that the MOR undergoes the Langmuir-Hinshelwood mechanism, whereby adsorbed CO is removed with the assistance of adsorbed OH. Within the PtNi catalyst, Pt provides methanol adsorption sites (in which methanol is converted to adsorbed CO) and Ni provides OH adsorption sites. The optimized Pt-Ni ratio for MOR was found to be 1:1. This suggests that bifunctional catalysts with both CO and OH adsorption sites can lead to highly active MOR catalysts.展开更多
Although nanostructures based on noble metal alloys are widely utilized in (electro)catalysis, their low-temperature synthesis remains an enormous challenge due to the different Nernst equilibrium potentials of meta...Although nanostructures based on noble metal alloys are widely utilized in (electro)catalysis, their low-temperature synthesis remains an enormous challenge due to the different Nernst equilibrium potentials of metal precursors. Herein, we describe the successful synthesis of trimetallic PtRhNi alloy nanoassemblies (PtRhNi-ANAs) with tunable Pt/Rh ratios using a simple mixed cyanogel reduction method and provide a detailed characterization of their chemical composition, morphology, and structure. Additionally, the electrochemical properties of PtRhNi-ANAs are examined by cyclic voltammetry, revealing composition- dependent electrocatalytic activity in the ethanol oxidation reaction (EOR). Compared to a commercial Pt black electrocatalyst, optimized Pt3Rh1Ni2-ANAs display remarkably enhanced EOR electrocatalytic performance in alkaline media.展开更多
The development of active and methanol-tolerant cathode electrocatalysts for the oxygen reduction reaction (ORR) is extremely important for accelerating the commercial viability of direct methanol fuel cells (DMFCs...The development of active and methanol-tolerant cathode electrocatalysts for the oxygen reduction reaction (ORR) is extremely important for accelerating the commercial viability of direct methanol fuel cells (DMFCs). In this work, we present an efficient and template-free route for facile synthesis of cyanide (CN^-)-functionalized PtNi hollow nanospheres (PtNi@CN HNSs) with a high alloying degree using a simple cyanogel reduction method at room temperature. The physical and electrocatalytic properties of the PtNi@CN HNSs were investigated by various physical and electrochemical techniques. The PtNi@CN HNSs exhibited significantly enhanced electrocatalytic activity, durability, and particular methanol tolerance for the ORR as compared to commercial Pt black, and thus they are promising cathode electrocatalysts for DMFCs.展开更多
A desirable methanol oxidation electrocatalyst was fabricated by metal atom diffusion to form an alloy of an assembled three-dimensional (3D) radial nanostructure of SnNi nanoneedles loaded with SnNiPt nanoparticles...A desirable methanol oxidation electrocatalyst was fabricated by metal atom diffusion to form an alloy of an assembled three-dimensional (3D) radial nanostructure of SnNi nanoneedles loaded with SnNiPt nanoparticles (NPs).Herein,metal atom diffusion occurred between the SnNi support and loaded Pt NPs to form a SnNiPt ternary alloy on the catalyst surface.The as-obtained catalyst combines the excellent catalytic performance of the alloy and advantages of the 3D nanostructure;the SnNiPt NPs,which fused on the surface of the SnNi nanoneedle support,can dramatically improve the availability of Pt during electrocatalysis,and thus elevate the catalytic activity.In addition,the efficient mass transfer of the 3D nanostructure reduced the onset potential.Furthermore,the catalyst achieved a favorable CO poisoning resistance and enhanced stability.After atomic interdiffusion,the catalytic activity drastically increased by 45%,and the other performances substantially improved.These results demonstrate the significant advantage and enormous potential of the atomic interdiffusion treatment in catalytic applications.展开更多
Four kinds of CuO catalysts with well-controlled leaf-like (L-CuO), flower-like (F-CuO), sea-urchin-like (U-CuO), and oatmeal-like (O-CuO) morphologies were synthesized by a facile precipitation method assiste...Four kinds of CuO catalysts with well-controlled leaf-like (L-CuO), flower-like (F-CuO), sea-urchin-like (U-CuO), and oatmeal-like (O-CuO) morphologies were synthesized by a facile precipitation method assisted by various chelating ligands. High-resolution transmission electron microscopy and fast Fourier transform infrared spectroscopy indicated that the dominant crystal facets of L-CuO, F-CuO, U-CuO, and O-CuO were {001}, {110}, {001}, and {110}, as well as {001} and {110}, respectively. When tested for the Rochow reaction, it was found that their catalytic performances were dependent on their structures. Among the four CuO catalysts, L-CuO exhibited the best catalytic property, along with the strongest adsorption ability for oxygen and highest reducibility, which are mainly because of its largely exposed {001} facet and large specific surface area. In addition, the amount of the Cu3Si alloy phase, which is the most important reaction intermediate that generated in the reacted region of the Si surface, was measured for the different catalysts. Based on the findings, a detailed reaction mechanism was proposed. This work demonstrates that shape-controlled synthesis of oxide catalysts could be an effective strategy to design and develop efficient catalysts.展开更多
Development of high-performance oxygen reduction reaction (ORR) catalysts is crucial to improve proton exchange membrane fuel cells. Herein, a multicomponent nanoporous PdCuTiA1 (np-PdCuTiA1) electrocatalyst has b...Development of high-performance oxygen reduction reaction (ORR) catalysts is crucial to improve proton exchange membrane fuel cells. Herein, a multicomponent nanoporous PdCuTiA1 (np-PdCuTiA1) electrocatalyst has been synthesized by a facile one-step dealloying strategy. The np-PdCuTiA1 catalyst exhibits a three-dimensional bicontinuous interpenetrating ligament/channel structure with an ultrafine length scale of -3.7 nm. The half-wave potential of np PdCuTiA1 is 0.873 V vs. RHE, more positive than those of PdC (0.756 V vs. RHE) and PtC (0.864 V vs. RHE) catalysts. The np-PdCuTiAl alloy shows a 4-electron reaction pathway with similar Tafel slopes to PtC. Remarkably, the half-wave potential shows a negative shift of only 12 mV for np-PdCuTiA1 in the presence of methanol, and this negative shift is much lower than those of the PdC (50 mV) and PtC (165 mV) catalysts. The enhanced ORR activity of np-PdCuTiA1 has been further rationalized through density functional theory calculations.展开更多
文摘Based on the alloy Cu55Ni45 (at pct), holding the proportion of Cu to Ni in constant and in the temperature range of 1233~1573 K, the wetting angles of CuNi-0~56 at pct Ti alloys on Si3N4 have been measured by the sessile drop method. With the increase of Ti content, the wetting angles decreased. The equilibrium wetting angle was 5° when Ti content ≥32 at pct.In the case of same Ti content, the activity of Ti in CuNiTi alloy was weaker than that in CuTi alloy The cross-section of the CuNiTi-Si3N4 interface and the elements distribution were examined by scanning electron microscope with X-ray wave-dispersion spectrometer, and the reaction products formed at the interface were determined by X-ray diffiaction analysis method.
基金the support from the National Natural Science Foundation of China(22179079 and 52101264)the Science and Technology Commission of Shanghai Municipality(20010500400)the Westlake Education Foundation。
文摘Sodium(Na)metal anode exhibits a potential candidate in next-generation rechargeable batteries owing to its advantages of high earth abundance and low cost.Unfortunately,the practical development of sodium metal batteries is inherently plagued by challenges such as the side reactions and the growth of Na dendrites.Herein we report a highly stable Bi-based“sodiophilic”substrate to stabilize Na anode,which is created by in-situ electrochemical reactions of 3D hierarchical porous Bi_(2)MoO_(6)(BMO)microspheres.BMO is initially transformed into the Bi“nanoseeds”embedded in the Na-Mo-O matrix.Subsequently,the Bi nanoseeds working as preferential nucleation sites through the formation of BiNa alloy enable the non-dendritic Na deposition.The asymmetric cells based on such BMO-based substrate can deliver a long-term cycling for 600 cycles at a large capacity of 4 m Ah cm^(-2) and for 800 cycles at a high current density of 10 m A cm^(-2).Even at a high depth of discharge(66.67%),the Na-predeposited BMO(Na@BMO)electrodes can cycle for more than 1600 h.The limited Na@BMO anodes coupled with the Na_(3)V_(2)(PO_(4))_(3) cathodes(N/P ratio of 3)in full cells also show excellent electrochemical performance with a capacity retention of about 97.4%after 1100 cycles at 2 C.
基金This work is financially supported by the National Natural Science Foundation of China(Grant Nos.52072137,51802105).
文摘Tin (Sn) metal foil is a promising anode for next-generation high-energy–density lithium-ion batteries (LIBs) due to its high capacity and easy processibility. However, the pristine Sn foil anode suffers nonuniform alloying/dealloying reaction with lithium (Li) and huge volume variation, leading to electrode pulverization and inferior electrochemical performance. Herein, we proposed that reduced grain size and elaborate porosity design of Sn foil can circumvent the nonuniform alloy reaction and buffer the volume change during the lithiation/delithiation cycling. Experimentally, we designed a three-dimensional interconnected porous Sn (3DIP-Sn) foil by a facile chemical alloying/dealloying approach, which showed improved electrochemical performance. The enhanced structure stability of the as-fabricated 3DIP-Sn foil was verified by chemo-mechanical simulations and experimental investigation. As expected, the 3DIP-Sn foil anode revealed a long cycle lifespan of 4400 h at 0.5 mA cm^(−2) and 1 mAh cm^(−2) in Sn||Li half cells. A 3DIP-Sn||LiFePO_(4) full cell with LiFePO_(4) loading of 7.1 mg cm^(−2) exhibited stable cycling for 500 cycles with 80% capacity retention at 70 mA g^(−1). Pairing with high-loading commercial LiNi0.6Co0.2Mn0.2O_(2) (NCM622, 18.4 mg cm^(−2)) cathode, a 3DIP-Sn||NCM622 full cell delivered a high reversible capacity of 3.2 mAh cm^(−2). These results demonstrated the important role of regulating the uniform alloying/dealloying reaction and circumventing the localized strain/stress in improving the electrochemical performance of Sn foil anodes for advanced LIBs.
基金Funded by the National Natural Science Foundation of China(No.51304198)Natural Science Foundation of Jiangsu Province(Nos.2013106,20141134 and 2014028-08)
文摘Pouring temperature and time are the most important influencing factors on interfacial reaction during the centrifugal casting. When cast at high temperatures, the crucible becomes brittle and prone to cracking, and shows a low stability. In this paper, we studied the centrifugal casting of Ti-47.5-Al-2.5V-1Cr alloy, and explored the effects of pouring temperature on the interfacial reaction. Castings at 1 600, 1 650, and 1 700 ℃ were obtained by controlling the other parameters constant in the experiments. The microstructure, elemental distribution, thickness of the reaction layer and phase composition of the castings at the interface were studied. The results show that the thickness at the interfacial reaction layer is increased by raising the pouring temperature. The elements in the mold and the matrix were double-diffused and reacted at the interface during the casting process, and formed solid solutions with the precipitation of many new phases such as AlOand TiO. The roughness of interface structure and layer thickness of reaction increase with the rise of temperature, and the interfacial reaction is more intense. There is a minimum layer thickness of the reaction layer that is 80 μm when the temperature is 1 600 ℃.
基金financially supported by the National Natural Science Foundation of China (No. 51274039)the Guangdong Foundation of Research (No. 2011A090200091)
文摘In this paper, TiAl alloy powders were prepared successfully by high-energy ball milling and diffusion reaction in vacuum at low temperature. The titanium powder, aluminum powder, and titanium hydride powder were used as raw materials. The samples were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD), field-emission scanning electron microscopy(FESEM), and differential thermal analysis(DTA). The results show that the alloy powders with the main intermetallic compounds of TiAl are obtained using Ti-Al powders and TiH2-Al powders after heated for 2 h at 500 ℃,3 h at 600 ℃,and 3 h at 750 ℃,respectively.The average grain sizes of alloy powder are about 45 and20 μm with irregular shape, respectively. The prepared TiAl alloy powders are relatively pure, and the average quality content of oxygen in the alloy powders is0.33 wt%. The forming process of alloy powder contains both the diffusion reaction of Ti and Al,which gives priority to the diffusion reaction of aluminum.
基金We acknowledge support from the National Science Foundation (NSF) through award DMR-1437263 on catalysis studies and the Office of Naval Research (ONR) under award N00014-15-1-2146 for synthesis efforts. X. F. D. acknowledges support from the U.S. Department of Energ34 Office of Basic Energy Sciences, Division of Materials Science and Engineering through award DE-SC0008055. E. B. Z. received additional support from China Scholarship Council (CSC) scholarships. We also thank the Electron Imaging Center of Nanomachines at CNSI for TEM support.
文摘Controlled syntheses of PtNi metal nanocrystals with unique structures for catalyzing oxygen reduction reactions (ORRs) have attracted great interest. Here, we report the one-step synthesis of single-crystal PtNi octahedra with in situ-developed highly concave features and self-confined composition that are optimal for ORR. Detailed studies revealed that the Pt-rich seeding, subsequent Pt/Ni co-reduction, and Pt-Ni interfusion resulted in uniform single-crystal PtNi octahedra, and that the combination of Ni facet segregation and oxygen etching of a Ni-rich surface led to the concavity and confined Ni content. The concave PtNi nanocrystals exhibited much higher ORR performance than the commercially available Pt/C catalyst in terms of both specific activity (29.1 times higher) and mass activity (12.9 times higher) at 0.9 V (vs. reversible hydrogen electrode (RHE)). The performance was also higher than that of PtNi octahedra without concavity, confirming that the higher activity was closely related to its morphology. Moreover, the concave octahedra also exhibited remarkable stability in ORR (93% mass activity remained after 10,000 cycles between 0.6 and 1.1 V vs. RHE) owing to the passivation of the unstable sites.
基金This work was financially supported by the National Key Research and Development Program of China (No. 2017YFA0206500), the National Natural Science Foundation of China (No. 21671014), State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology (No. oic-201503003) and the Fundamental Research Funds for the Central Universities (No. buctrc201522).
文摘High performance methanol oxidation reaction (MOR) catalysts are critical to the performance of attractive, direct methanol fuel cells. Here, we use surface controlled PtNi alloy nanoparticles as model catalysts to study the MOR mechanism and give further guidance to the design of new high performance MOR catalysts. The enhanced MOR activity of PtNi alloy was mainly attributed to the enhanced OH adsorption owing to surface Ni sites. This suggests that the MOR undergoes the Langmuir-Hinshelwood mechanism, whereby adsorbed CO is removed with the assistance of adsorbed OH. Within the PtNi catalyst, Pt provides methanol adsorption sites (in which methanol is converted to adsorbed CO) and Ni provides OH adsorption sites. The optimized Pt-Ni ratio for MOR was found to be 1:1. This suggests that bifunctional catalysts with both CO and OH adsorption sites can lead to highly active MOR catalysts.
基金Acknowledgements We acknowledge financial support by the National Natural Science Foundation of China (Nos. 21473111 and 21376122), Fundamental Research Funds for the Central Universities (No. GK201602002), Innovation Foundation of Shenzhen Government (No. JCYJ20160408173202143), the Joint Fund of Energy Storage of Qingdao (No. 20160012), and the Fundamental Research Funds of Huazhong University of Science and Technology (Nos. 3004013109 and 0118013089). We acknowledge the support of Analytical and Testing Center of Huazhong University of Science and Technology for SEM and XPS measurements.
文摘Although nanostructures based on noble metal alloys are widely utilized in (electro)catalysis, their low-temperature synthesis remains an enormous challenge due to the different Nernst equilibrium potentials of metal precursors. Herein, we describe the successful synthesis of trimetallic PtRhNi alloy nanoassemblies (PtRhNi-ANAs) with tunable Pt/Rh ratios using a simple mixed cyanogel reduction method and provide a detailed characterization of their chemical composition, morphology, and structure. Additionally, the electrochemical properties of PtRhNi-ANAs are examined by cyclic voltammetry, revealing composition- dependent electrocatalytic activity in the ethanol oxidation reaction (EOR). Compared to a commercial Pt black electrocatalyst, optimized Pt3Rh1Ni2-ANAs display remarkably enhanced EOR electrocatalytic performance in alkaline media.
基金This research was sponsored by National Natural Science Foundation of China (Nos. 21473111 and 21376122), Natural Science Foundation of Shaanxi Province (No. 2015JM2043), and Fundamental Research Funds for the Central Universities (No. GK201602002).
文摘The development of active and methanol-tolerant cathode electrocatalysts for the oxygen reduction reaction (ORR) is extremely important for accelerating the commercial viability of direct methanol fuel cells (DMFCs). In this work, we present an efficient and template-free route for facile synthesis of cyanide (CN^-)-functionalized PtNi hollow nanospheres (PtNi@CN HNSs) with a high alloying degree using a simple cyanogel reduction method at room temperature. The physical and electrocatalytic properties of the PtNi@CN HNSs were investigated by various physical and electrochemical techniques. The PtNi@CN HNSs exhibited significantly enhanced electrocatalytic activity, durability, and particular methanol tolerance for the ORR as compared to commercial Pt black, and thus they are promising cathode electrocatalysts for DMFCs.
基金This work was financially supported by the National Natural Science Foundation of China (Nos. 21771140, 21471114, 91122103 and 51271132).
文摘A desirable methanol oxidation electrocatalyst was fabricated by metal atom diffusion to form an alloy of an assembled three-dimensional (3D) radial nanostructure of SnNi nanoneedles loaded with SnNiPt nanoparticles (NPs).Herein,metal atom diffusion occurred between the SnNi support and loaded Pt NPs to form a SnNiPt ternary alloy on the catalyst surface.The as-obtained catalyst combines the excellent catalytic performance of the alloy and advantages of the 3D nanostructure;the SnNiPt NPs,which fused on the surface of the SnNi nanoneedle support,can dramatically improve the availability of Pt during electrocatalysis,and thus elevate the catalytic activity.In addition,the efficient mass transfer of the 3D nanostructure reduced the onset potential.Furthermore,the catalyst achieved a favorable CO poisoning resistance and enhanced stability.After atomic interdiffusion,the catalytic activity drastically increased by 45%,and the other performances substantially improved.These results demonstrate the significant advantage and enormous potential of the atomic interdiffusion treatment in catalytic applications.
文摘Four kinds of CuO catalysts with well-controlled leaf-like (L-CuO), flower-like (F-CuO), sea-urchin-like (U-CuO), and oatmeal-like (O-CuO) morphologies were synthesized by a facile precipitation method assisted by various chelating ligands. High-resolution transmission electron microscopy and fast Fourier transform infrared spectroscopy indicated that the dominant crystal facets of L-CuO, F-CuO, U-CuO, and O-CuO were {001}, {110}, {001}, and {110}, as well as {001} and {110}, respectively. When tested for the Rochow reaction, it was found that their catalytic performances were dependent on their structures. Among the four CuO catalysts, L-CuO exhibited the best catalytic property, along with the strongest adsorption ability for oxygen and highest reducibility, which are mainly because of its largely exposed {001} facet and large specific surface area. In addition, the amount of the Cu3Si alloy phase, which is the most important reaction intermediate that generated in the reacted region of the Si surface, was measured for the different catalysts. Based on the findings, a detailed reaction mechanism was proposed. This work demonstrates that shape-controlled synthesis of oxide catalysts could be an effective strategy to design and develop efficient catalysts.
文摘Development of high-performance oxygen reduction reaction (ORR) catalysts is crucial to improve proton exchange membrane fuel cells. Herein, a multicomponent nanoporous PdCuTiA1 (np-PdCuTiA1) electrocatalyst has been synthesized by a facile one-step dealloying strategy. The np-PdCuTiA1 catalyst exhibits a three-dimensional bicontinuous interpenetrating ligament/channel structure with an ultrafine length scale of -3.7 nm. The half-wave potential of np PdCuTiA1 is 0.873 V vs. RHE, more positive than those of PdC (0.756 V vs. RHE) and PtC (0.864 V vs. RHE) catalysts. The np-PdCuTiAl alloy shows a 4-electron reaction pathway with similar Tafel slopes to PtC. Remarkably, the half-wave potential shows a negative shift of only 12 mV for np-PdCuTiA1 in the presence of methanol, and this negative shift is much lower than those of the PdC (50 mV) and PtC (165 mV) catalysts. The enhanced ORR activity of np-PdCuTiA1 has been further rationalized through density functional theory calculations.