The Experts below are selected from a list of 27426 Experts worldwide ranked by ideXlab platform
Qiang Zhang - One of the best experts on this subject based on the ideXlab platform.
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framework porphyrin derived single atom bifunctional oxygen Electrocatalysts and their applications in zn air batteries
Advanced Materials, 2019Co-Authors: Changxin Zhao, Shuangming Chen, Jianing Liu, Xiao Chen, Li Song, Qiang ZhangAbstract:High-performance bifunctional oxygen electrocatalysis constitutes the key technique for the widespread application of clean and sustainable energy through electrochemical devices such as rechargeable Zn-air batteries. Single-atom Electrocatalysts with maximum atom efficiency are highly considered as an alternative of the present noble-metal-based Electrocatalysts. However, the fabrication of transition metal single-atoms is very challenging, requiring extensive attempts of precursors with novel design principles. Herein, an all-covalently constructed cobalt-coordinated framework porphyrin with graphene hybridization is innovatively designed and prepared as the pyrolysis precursor to fabricate single-atom Co-Nx -C Electrocatalysts. Excellent electrochemical performances are realized for both bifunctional oxygen electrocatalysis and rechargeable Zn-air batteries with regard to reduced overpotentials, improved kinetics, and prolonged cycling stability comparable with noble-metal-based Electrocatalysts. Design principles from multiple scales are proposed and rationalized with detailed mechanism investigation. This work not only provides a novel precursor for the fabrication of high-performance single-atom Electrocatalysts, but also inspires further attempts to develop advanced materials and emerging applications.
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regulating p block metals in perovskite nanodots for efficient electrocatalytic water oxidation
Nature Communications, 2017Co-Authors: Zijing Xia, Bingsen Zhang, Cheng Tang, Haofan Wang, Qiang ZhangAbstract:Water oxidation represents the core process of many sustainable energy systems, such as fuel cells, rechargeable metal-air batteries, and water splitting. Material surface defects with high-energy hanging bonds possess superb intrinsic reactivity, whose actual performance is limited by the dimension and conductivity of the electrocatalyst. Herein we propose a surface defect-rich perovskite electrocatalyst through a p-block metal regulation concept to achieve high performance for oxygen evolution. As a typical p-metal, Sn4+ dissolves from the solid phase from model SnNiFe perovskite nanodots, resulting in abundant surface defects with superior water oxidation performance. An oxygen pool model and a fusion-evolution mechanism are therefore proposed for the in-depth understanding of p-block metal regulation and the oxygen evolution reaction. The energy chemistry unveiled herein provides insights into water oxidation and helps to tackle critical issues in multi-electron oxygen electrocatalysis. Electrocatalysts that possess high densities of surface defects show great promise for efficient water oxidation. Here the authors demonstrate that regulating the p-block metal content in perovskite nanodots imparts these materials with abundant surface defects and excellent electrocatalytic activity.
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bifunctional transition metal hydroxysulfides room temperature sulfurization and their applications in zn air batteries
Advanced Materials, 2017Co-Authors: Haofan Wang, Cheng Tang, Bin Wang, Qiang ZhangAbstract:Bifunctional electrocatalysis for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) constitutes the bottleneck of various sustainable energy devices and systems like rechargeable metal–air batteries. Emerging catalyst materials are strongly requested toward superior electrocatalytic activities and practical applications. In this study, transition metal hydroxysulfides are presented as bifunctional OER/ORR Electrocatalysts for Zn–air batteries. By simply immersing Co-based hydroxide precursor into solution with high-concentration S2−, transition metal hydroxides convert to hydroxysulfides with excellent morphology preservation at room temperature. The as-obtained Co-based metal hydroxysulfides are with high intrinsic reactivity and electrical conductivity. The electron structure of the active sites is adjusted by anion modulation. The potential for 10 mA cm−2 OER current density is 1.588 V versus reversible hydrogen electrode (RHE), and the ORR half-wave potential is 0.721 V versus RHE, with a potential gap of 0.867 V for bifunctional oxygen electrocatalysis. The Co3FeS1.5(OH)6 hydroxysulfides are employed in the air electrode for a rechargeable Zn–air battery with a small overpotential of 0.86 V at 20.0 mA cm−2, a high specific capacity of 898 mAh g−1, and a long cycling life, which is much better than Pt and Ir-based electrocatalyst in Zn–air batteries.
Sanjeev Mukerjee - One of the best experts on this subject based on the ideXlab platform.
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role of structural and electronic properties of pt and pt alloys on electrocatalysis of oxygen reduction an in situ xanes and exafs investigation
Journal of The Electrochemical Society, 1995Co-Authors: Sanjeev Mukerjee, Manuel P Soriaga, S Srinivasan, J McbreenAbstract:The electrocatalysis of the oxygen reduction reaction (ORR) on five binary Pi alloys (PtCr/C, PtMn/C, PtFe/C, PtCo/C, and PtNi/C) supported on high surface area carbon in a proton exchange membrane fuel cell was investigated. All the alloy Electrocatalysts exhibited a high degree of crystallinity with the primary phase of the type Pt3M (LI2 structure with fcc type lattice) and a secondary phase (only minor contribution from this phase) being of the type PtM (LIo structure with tetragonal lattice) as evidenced from x-ray powder diffraction (XRD) analysis. The electrode kinetic studies on the Pt alloys at 95~ and 5 atm pressure showed a two- to threefold increase in the exchange current densities and the current density at 900 mV as well as a decrease in the overvoltage at i0 mA em -2 relative to Pt/C eleetrocatalyst. The PtCr/C alloy exhibited the best performance. In situ EXAFS and XANES analysis at potentials in the double-layer region [0.54 V vs. reversible hydrogen electrode (RHE)] revealed (i) all the alloys possess higher Pt d-band vacancies per atom (with the exception of PtMn/C alloy) relative to Pt/C electrocatalyst and (it) contractions in the Pt-Pt bond distances which confirmed the results from ex situ XRD analysis. A potential excursion to 0.84 V vs. RHE showed that, in contrast to the Pt alloys, the Pt/C electrocatalyst exhibits a significant increase in the Pt d-band vacancies per atom. This increase, in Pt/C has been rationalized as being due to adsorption of OH species from the electrolyte following a Temkin isotherm behavior, which does not occur on the Pt alloys. Correlation of the electronic (Pt d-band vacancies) and geometric (Pt-Pt bond distance) with the electrochemical performance characteristics exhibits a volcano type behavior with the PtCr/C alloy being at the top of the curve. The enhanced electrocatalysis by the alloys therefore can be rationalized on the basis of the interplay between the electronic and geometric factors on one hand and their effect on the chemisorption behavior of OH species from the electrolyte. The role of Pt/C and Pt alloys on the mechanism of the oxygen reduction reaction (ORR) has been investigated previously, 1-4 however the mechanism still remains elusive. One of the first investigations I of the ORR on Pt alloy Electrocatalysts was in phosphoric acid; the effect of changes in the Pt-Pt interatomic distances, caused by alloying, was examined. The strength of the [M-HO2]aas bond, the intermediate formed in the rate-determining step of the molecular dioxygen reduction, was shown to depend on the Pt-Pt bond distance in the alloys. A plot of the electrocatalytic activity vs. adsorbate bond strength exhibited a volcano type behavior. 5 It was shown that the lattice contractions due to alloying resulted in a more favorable Pt-Pt distance (while maintaining the favorable Pt electronic properties) for dissociative adsorption of 02. This view was disputed by Glass et al. ~ in their investigation on bulk alloys of PtCr (the binary alloy at the top of the volcano plot) of different compositions. The latter investigation showed no activity enhancement for the ORR in phosphoric acid. This study therefore suggested the possibility of differences in electrochemical properties of bulk vs. supported alloy Electrocatalysts (small particles of 35-85 A). A recent study on supported PtCo Electrocatalysts ~ revealed the possibility that particle termination, primarily at the vicinal planes in the supported alloy electrocatalyst, is the reason for the enhanced ORR electrocatalysis (i.e., vicinal planes are more active than ). Paffett et al., 3 attributed higher activities for the ORR on bulk PtCr alloys in phosphoric acid to surface roughening, and hence increased Pt surface area, caused by the dissolution of the more oxidizable alloying component Cr. In contrast to these findings on bulk alloys, the supported alloy Electrocatalysts have been reported to retain their nonnoble alloying element in the electrode during long periods (6000-9000 h) of operation in phosphoric acid fuel cells (PAFCs) 6 and proton exchange membrane fuel ceils (PEMFCs). 7 Based on these previous investigations and in the context of the ORR mechanisms, the principle explanations for the
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Enhanced electrocatalysis of oxygen reduction on platinum alloys in proton exchange membrane fuel cells
Journal of Electroanalytical Chemistry, 1993Co-Authors: Sanjeev Mukerjee, Supramaniam SrinivasanAbstract:Enhanced electrocatalysis of the oxygen reduction reaction (ORR) on carbon-supported binary and ternary alloys of Pt in phosphoric acid fuel cells has been reported previously. This investigation focuses on the electrocatalysis of the ORR on some binary alloys of Pt (Pt+Ni, Pt+Cr and Pt+Co) at interfaces with proton exchange membranes (Dow perfluorinated sulfonic acids). Comparison of the results of these studies with those on carbon-supported Pt Electrocatalysts (electrodes containing same Pt loading of 0.3 mg/cm2) revealed enhanced activities, lower activation energies and different reaction orders for all the alloys. X-ray powder diffraction showed lattice contractions for the alloys, the predominant phase being Pt3M (LI2) f.c.c. crystalline. X-ray photoelectron spectroscopy studies on the constituent elements of the electrocatalyst showed no chemical energy shifts owing to alloying and/or the presence of oxides on the surface. Lifetime evaluations of proton exchange membrane fuel cells, using both electrochemical as well as scanning electron microscopy/energy-dispersive X-ray analysis techniques, revealed only small amounts of dissolution of the more oxidizable component during the testing periods, which ranged from 400 to 1200 h. Therefore, the enhanced electrocatalysis exhibited by the binary Pt alloys appears to originate primarily as a result of changes in the lattice structure owing to alloying and the unique environment of the supported catalyst in the particle size range 35–75 A.
Zongping Shao - One of the best experts on this subject based on the ideXlab platform.
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interfacial la diffusion in the ceo2 lafeo3 hybrid for enhanced oxygen evolution activity
ACS Applied Materials & Interfaces, 2021Co-Authors: Yawen Dai, Zhenbao Zhang, Chun Cheng, Peng Tan, Zongping ShaoAbstract:The electrochemical oxygen evolution reaction (OER) is of great significance for energy conversion and storage. The hybrid strategy is attracting increasing interest for the development of highly active OER Electrocatalysts. Regarding the activity enhancement mechanism, electron coupling between two phases in hybrids has been widely reported, but the interfacial elemental redistribution is rarely investigated. Herein, we developed a CeO2/LaFeO3 hybrid electrocatalyst for enhanced OER activity. Interestingly, a selective interfacial La diffusion from LaFeO3 to CeO2 was demonstrated by the electron energy loss spectra and elemental mapping. This redistribution of cations triggers the change of the chemical environment of interface elements for charge compensation because of the electroneutrality principle, which results in increased oxygen vacancies and high-valent Fe species that promote the OER electrocatalysis. This mechanism might be extended to other hybrid systems and inspire the design of more efficient Electrocatalysts.
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scandium and phosphorus co doped perovskite oxides as high performance Electrocatalysts for the oxygen reduction reaction in an alkaline solution
Journal of Materials Science & Technology, 2020Co-Authors: Meigui Xu, Wei Wang, Yujuan Shen, Wei Zhou, Jun Wang, Zhigang Chen, Zongping ShaoAbstract:Abstract The requirement for a sustainable and renewable energy has inspired substantial interests in designing and developing earth-abundant and high-effectiveness Electrocatalysts/electrodes for fuel cells and metal-air batteries, in which oxygen reduction reaction (ORR) plays a crucial role. Perovskite oxides have acquired rapid attention as ORR Electrocatalysts to replace noble-metal-based catalysts owing to their intrinsic electrocatalytic activity, compositional and structural flexibility. Herein, we report a new Sc and P co-doped perovskite oxide (La0.8Sr0.2Mn0.95Sc0.025P0.025O3-δ, LSMSP) as an active and robust electrocatalyst for the ORR in an alkaline solution. LSMSP electrocatalyst shows superior ORR activity and stability than those of pristine La0.8Sr0.2MnO3-δ (LSM), Sc-doped LSM and P-doped LSM due to the optimized average valence of Mn ions, the large surface area, the smaller particle size and the synergetic effect introduced by the co-doping. Moreover, compared to the benchmark Pt/C electrocatalyst, LSMSP electrocatalyst displays comparable ORR activity and superior durability. These above results suggest that the co-doping strategy of Sc and P into perovskites is a useful method to design high-performance Electrocatalysts for the ORR, which can be used in other electrocatalysis-based applications.
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srco0 9ti0 1o3 δ as a new electrocatalyst for the oxygen evolution reaction in alkaline electrolyte with stable performance
ACS Applied Materials & Interfaces, 2015Co-Authors: Chao Su, Yubo Chen, Xiaomin Xu, Guangming Yang, Moses O. Tadé, Zongping ShaoAbstract:The development of efficient, inexpensive, and stable Electrocatalysts for the oxygen evolution reaction (OER) is critical for many electrochemical energy conversion technologies. The prohibitive price and insufficient stability of the state-of-the-art IrO2 electrocatalyst for the OER inhibits its use in practical devices. Here, SrM0.9Ti0.1O3−δ (M = Co, Fe) perovskites with different B-site transition metal elements were investigated as potentially cheaper OER Electrocatalysts. They were prepared through a typical sol–gel route, and their catalytic activities for the OER in alkaline medium were comparatively studied using rotating disk electrodes. Both materials show high initial intrinsic activities in alkaline electrolyte for the OER, comparable to the benchmark perovskite-type electrocatalyst Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF), but SrCo0.9Ti0.1O3−δ (SCT) possessed more operational stability than SrFe0.9Ti0.1O3−δ (SFT), even better than BSCF and IrO2 catalysts. Based on the X-ray photoelectron spectra anal...
Supramaniam Srinivasan - One of the best experts on this subject based on the ideXlab platform.
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Enhanced electrocatalysis of oxygen reduction on platinum alloys in proton exchange membrane fuel cells
Journal of Electroanalytical Chemistry, 1993Co-Authors: Sanjeev Mukerjee, Supramaniam SrinivasanAbstract:Enhanced electrocatalysis of the oxygen reduction reaction (ORR) on carbon-supported binary and ternary alloys of Pt in phosphoric acid fuel cells has been reported previously. This investigation focuses on the electrocatalysis of the ORR on some binary alloys of Pt (Pt+Ni, Pt+Cr and Pt+Co) at interfaces with proton exchange membranes (Dow perfluorinated sulfonic acids). Comparison of the results of these studies with those on carbon-supported Pt Electrocatalysts (electrodes containing same Pt loading of 0.3 mg/cm2) revealed enhanced activities, lower activation energies and different reaction orders for all the alloys. X-ray powder diffraction showed lattice contractions for the alloys, the predominant phase being Pt3M (LI2) f.c.c. crystalline. X-ray photoelectron spectroscopy studies on the constituent elements of the electrocatalyst showed no chemical energy shifts owing to alloying and/or the presence of oxides on the surface. Lifetime evaluations of proton exchange membrane fuel cells, using both electrochemical as well as scanning electron microscopy/energy-dispersive X-ray analysis techniques, revealed only small amounts of dissolution of the more oxidizable component during the testing periods, which ranged from 400 to 1200 h. Therefore, the enhanced electrocatalysis exhibited by the binary Pt alloys appears to originate primarily as a result of changes in the lattice structure owing to alloying and the unique environment of the supported catalyst in the particle size range 35–75 A.
Jing Wang - One of the best experts on this subject based on the ideXlab platform.
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high density iron nanoparticles encapsulated within nitrogen doped carbon nanoshell as efficient oxygen electrocatalyst for zinc air battery
Nano Energy, 2015Co-Authors: Jing Wang, Shu Miao, Haihua Wu, Guoxiong WangAbstract:Abstract Exploring highly efficient Electrocatalysts toward oxygen reduction and evolution reactions are critical for the development of rechargeable zinc–air batteries. As a novel class of electrocatalyst, transition metal nanoparticles encapsulated within nitrogen-doped carbon have been regarded as competitive alternative to replace noble metal Electrocatalysts. Herein, we report successful synthesis of high-density iron nanoparticles encapsulated within nitrogen-doped carbon nanoshell (Fe@N–C) by solid-phase precursor׳s pyrolysis of dicyandiamide and ammonium ferric citrate. The resulting Fe@N–C material shows excellent bifunctionality for ORR and OER in alkaline medium compared to state-of-the-art commercial Pt/C and IrO2, which demonstrates high performance and cycling durability in zinc–air battery as efficient oxygen electrocatalyst.
