The Volkswagen emissions scandal began in 2015, when the U.S. Environmental Protection Agency announced that diesel cars produced by Volkswagen from 2009 through 2015 were in violation of emissions ...standards. The authors analyze the impact of this announcement on transaction prices for Volkswagen cars on the U.S. eBay Motors. The main focus is on Volkswagen cars other than the 2009–2015 diesel models—namely, vehicles that did not violate agency standards, enabling an assessment of whether the negative shock received by the emissions standards violators spilled over to other Volkswagen models that were in compliance. The difference-in-differences results show that final bid prices declined after the announcement by 14% for nonviolating diesel cars and 9% for nonviolating gasoline cars. The analysis also provides little evidence of considerable changes in the numbers of participating bidders, bidding strategies, numbers of listings, and reserve-price strategies, suggesting that the drops in prices likely resulted from lowered willingness to pay from buyers.
We analyze the formation of rival leagues and deterrence by incumbent leagues in professional team sports, which is one of the least studied forms of competition in sports. We first survey the ...economic history of professional sport leagues in North America and develop stylized facts about rival league formation. We then develop a game-theoretical model to explain some of these interesting stylized facts, showing that if the bargaining power of the incumbent league is sufficiently small—i.e., less than a certain cutoff—the incumbent should choose expansion to deter the rival league formation; otherwise, it is optimal for the incumbent league to allow a rival league formation and then merge with it, conditional on rival league success. We further show that the incumbent league may pay players relatively high salaries as an alternative way to deter formation by a rival league.
We examine the problem of selling an object to a stream of potential buyers with independent private values and participation costs. If the object can be resold in the future, and resellers can make ...posted price offers, the original seller may prefer to deal with potential buyers sequentially instead of holding an auction. The reason is that resale opportunities compress the dispersion of buyers’ willingness to pay for the object, which lowers the surplus each buyer expects to receive in the auction. This effect may reduce participation in the initial auction to just one buyer, in which case the seller obtains zero revenue. We show that a simple form of sequential mechanism allows the seller to extract positive revenue, and becomes approximately optimal if the resale market is large. Our finding contrasts with the result that sellers usually prefer auctions when resale is not allowed (see Bulow and Klemperer in Am Econ Rev 99(4):1544–1575, 2009).
Display omitted
•The multifunctional cellulose/silica hybrid microcapsules were prepared via one-step emulsion-solvent diffusion.•The multifunctional fabric coating system is water-based and ...environmental friendly.•The fabric coating exhibits excellent superhydrophobicity, ultraviolet resistant and thermal insulation.•These coatings demonstrate the self-healing ability of superhydrophobicity and ultraviolet protection after damaged.
Exploiting water-based fabric coatings outfitted with multiple protections (e.g., waterproofness, ultraviolet (UV) resistance and thermal insulation) are urgently demanded. Nevertheless, achieving the multifunction and durability poses the major challenge. In the present study, novel multifunctional cellulose/silica hybrid microcapsules were developed by one-step emulsion-solvent diffusion; these microcapsules were well dispersed into waterborne silicone resins to form waterborne multiple protective fabric coatings. Since the encapsulated phase change materials were in the core of capsules, and the hydrophobic coupling reagent and UV absorber were grafted onto the silicas in the shell of capsules, these fabric coatings exhibited high superhydrophobicity, UV protection and thermal insulation. Moreover, because hydrophobic coupling reagent and UV absorber in the shell-cellulose of capsules exhibited easy mobility, the fabric coatings displayed self-repairability of superhydrophobicity and UV protection even after being damaged chemically or mechanically. The fabric coating presented in this study could have a range of applications, covering special protective fabric, high-altitude garments as well as self-cleaning materials.
Display omitted
•N-doped carbon nanosheets were fabricated via a facile templating-assisted strategy.•The N-doped carbon nanosheets showed superior performance in redox electrolytes.•Graphitic N on ...the carbon scaffolds can accelerate the redox kinetics of iodides.
The incorporation of redox-active anions into aqueous electrolytes endows electrodes with enhanced specific energy density for supercapacitors. However, the congruent relationship between the redox chemistry of electrolytes and electrode surfaces is still not well understood. Herein, two-dimensional nitrogen-doped porous carbon nanosheets (denoted as NC-x with x being the carbonization temperature in Degree Celsius) are systematically synthesized by using general dual-crystals templating assisted strategy with pore structure and surface composition optimized. Employed as both positive and negative electrodes, the as-prepared NC-900 with a large specific surface area and ample graphitic N sites shows a high specific capacitance of 251 F g−1 with a voltage window of 1.6 V and energy density of 22.4 Wh kg−1 associated with 86.5% capacity retention after 30,000 cycles using aqueous iodide redox electrolyte. The experimental and theoretical analyses reveal the contributions of nitrogen configurations on the carbon scaffolds to accelerate the redox chemistry of iodides. The enhanced redox performance of the porous carbon nanosheets is linearly proportional to the graphitic N content, which is consistent with the large electron-donating area and the strong adsorption capacity towards iodine species at the graphitic N sites. This work shows a new design strategy of carbon electrodes for high-performance supercapacitors with the aqueous redox electrolytes.
Zinc-ion hybrid capacitors (ZIHC) demonstrate impressive charge-storage performance and intrinsic safety due to the inherited superiorities of aqueous rechargeable batteries and supercapacitors. ...However, the promotion of electrochemical performance is usually hindered by the cathode materials that fail to hold high energy density and rate capability of ZIHC. The optimization of porous carbon cathodes into a hierarchical structure is an efficient strategy to break the bottlenecks of ZIHC. Herein, a metal oxide space-confined strategy is proposed to build 3D graphene-like porous carbon nanosheets (3DPC) with doping of O and S heteroatoms by using low-cost aromatic hydrocarbons as precursors. It is found that the obtained 3DPC consists of micro-, mseo- and macropores and further delivers a high specific surface area of 2813 m2 g−1 with a total pore volume of 1.82 cm3 g−1. Specifically, such a well-defined hierarchical porosity of 3DPC coupled with rich O and S heteroatoms enables sufficient multilevel ion transport channels and large accessible surface sites to capture the Zn2+ ions. As a proof of concept demonstration, the assembled aqueous ZIHC by employing the 3DPC cathode exhibits a desirable capacity of 194 mAh g−1 at 0.5 A g−1 with a superior rate capability of 53% at 30 A g−1 and excellent cycling stability of over 88% after 15000 cycles. Moreover, the remarkable electrochemical performance of the 3DPC cathode can be well-preserved in the case of a quasi-solid-state ZIHC device under various harsh bent states, highlighting the promising application in flexible and wearable energy storage.
Display omitted
•3D graphene-like porous carbon nanosheets (3DPC) were fabricated by a novel metal oxide space-confined strategy.•The obtained 3DPC with a hierarchical structure delivered a high surface area of 2813 m2 g−1 and rich O/S heteroatoms.•The 3DPC cathode exhibited a high specific capacity of 194 mAh g−1 with a superior rate capability and cycling stability.•The assembled quasi-solid-state ZIHC displayed desirable charge-storage performance and good mechanical flexibility.
Single‐atom catalysts (SACs) with specific N‐coordinated configurations immobilized on the carbon substrates have recently been verified to effectively alleviate the shuttle effect of lithium ...polysulfides (LiPSs) in lithium–sulfur (Li─S) batteries. Herein, a versatile molten salt (KCl/ZnCl2)‐mediated pyrolysis strategy is demonstrated to fabricate Zn SACs composed of well‐defined Zn‐N4 sites embedded into porous carbon sheets with rich pyridine‐N defects (Zn─N/CS). The electrochemical kinetic analysis and theoretical calculations reveal the critical roles of Zn‐N4 active sites and surrounding pyridine‐N defects in enhancing adsorption toward LiPS intermediates and catalyzing their liquid–solid conversion. It is confirmed by reducing the overpotential of the rate‐determining step of Li2S2 to Li2S and the energy barrier for Li2S decomposition, thus the Zn─N/CS guarantees fast redox kinetics between LiPSs and Li2S products. As a proof of concept demonstration, the assembled Li─S batteries with the Zn─N/CS‐based sulfur cathode deliver a high specific capacity of 1132 mAh g−1 at 0.1 C and remarkable capacity retention of 72.2% over 800 cycles at 2 C. Furthermore, a considerable areal capacity of 6.14 mAh cm−2 at 0.2 C can still be released with a high sulfur loading of 7.0 mg cm−2, highlighting the practical applications of the as‐obtained Zn─N/CS cathode in Li─S batteries.
Zinc-ion capacitors are high-performance hybrid capacitors that have great advantages because of the abundance of zinc resources and their high theoretical capacitance. As a result they have become a ...hot research topic in the field of energy storage devices. Carbon-based materials are usually used as the cathode materials for these capacitors because of the wide range of available materials, and their easily tuned surface properties and simple fabrication. This review summarizes recent research progress on carbon cathode materials for flexible/non-flexible zinc ion capacitors, and gives a concise description of their novel structures and outstanding performance. It then discusses research on the energy storage mechanisms in the cathode materials and suggests directions for the development of carbon cathodes for zinc-ion capacitors.
Single-atom catalysts (SACs) with specific N-coordinated configurations immobilized on the carbon substrates have recently been verified to effectively alleviate the shuttle effect of lithium ...polysulfides (LiPSs) in lithium-sulfur (Li─S) batteries. Herein, a versatile molten salt (KCl/ZnCl
)-mediated pyrolysis strategy is demonstrated to fabricate Zn SACs composed of well-defined Zn-N
sites embedded into porous carbon sheets with rich pyridine-N defects (Zn─N/CS). The electrochemical kinetic analysis and theoretical calculations reveal the critical roles of Zn-N
active sites and surrounding pyridine-N defects in enhancing adsorption toward LiPS intermediates and catalyzing their liquid-solid conversion. It is confirmed by reducing the overpotential of the rate-determining step of Li
S
to Li
S and the energy barrier for Li
S decomposition, thus the Zn─N/CS guarantees fast redox kinetics between LiPSs and Li
S products. As a proof of concept demonstration, the assembled Li─S batteries with the Zn─N/CS-based sulfur cathode deliver a high specific capacity of 1132 mAh g
at 0.1 C and remarkable capacity retention of 72.2% over 800 cycles at 2 C. Furthermore, a considerable areal capacity of 6.14 mAh cm
at 0.2 C can still be released with a high sulfur loading of 7.0 mg cm
, highlighting the practical applications of the as-obtained Zn─N/CS cathode in Li─S batteries.
PDF
