Transition metal sulfide/graphene-based composites show broad prospects as electrode materials for supercapacitors. To explore the energy storage mechanism of composites, and clarify the synergistic ...effect between transition metal sulfide and graphene, a series of composites have been synthesized by adjusting the addition of graphene oxide during the preparation of the composites. The results show that the addition of graphene can effectively inhibit the agglomeration of nickel-cobalt sulfide particles. Cyclic voltammetry revealed that the proportion of surface-controlled capacitance increases with the increase of graphene (from 64.04% to 89.01%). Graphene can significantly improve the capacitance and stability of composites, while exceed graphene degrades the properties of the composites. An asymmetric supercapacitor assembled with NC/rGO25S (adding 25 mg graphene oxide during material synthesis) and activated carbon (AC) provides high specific capacitance (199.3 F g −1 at 2 A g −1) and excellent cycle stability (maintaining 90.4% after 10 000 cycles at 10 A g −1). All in all, the mechanism exploration and performance optimization of NiCo2S4/rGO in this work are of great significance for the further development of nickel-cobalt sulfide/rGO materials.
•Confined growth of NiCo2S4 is achieved by adding appropriate amount of graphene during the synthesis of composites.•Revealing the synergies effects and separately capacitance contributions between nickle-cobalt sulfides and rGO.•Exploring the evolution of phase and morphology of the composite during material synthesis.•The nano-NiCo2S4/rGO with highly optimized performance is achieved and demonstrated in asymmetric supercapacitor.
The main goal of this work is to introduce a comparison between connected and confine MO-connected space, locally connected and confine MO-locally connected space, extremally disconnected and confine ...MO-extremally disconnected space, confine MO-first countable space and first countable space, confine MO-second countable space and second countable space. New properties and relations are introduced.
The TiO2 nanoclusters were modified into the pores of silica core-shell particles (SiO2@dSiO2) by the sol-gel method, and the loading amount reached 47%. Based on the Ostwald ripening theory, by ...simply extending the reaction time, a part of the TiO2 in the pores of the shell was dissolved and then re-deposited on the outer surface of the shell to form a TiO2 layer. Using this method, TiO2 crystalline grains of different sizes were obtained simultaneously inside and outside the shell of silica core-shell spheres. Small-sized crystalline grains were located in the pores of the shell, and they had a strong quantum size effect. The large crystalline grains were located in the TiO2 layer on the outer surface of the shell of SiO2@dSiO2. Due to the formation of larger-sized crystalline grains, the recombination probability of photogenerated electron-hole pairs was reduced. When used as photocatalysts for the degradation of Rhodamine B under UV irradiation, the catalytic activity of SiO2@dSiO2@TiO2 was 5.4 times higher than that of the commercial P25 TiO2 photocatalyst.
Display omitted
•Loading of TiO2 in core-shell silica particles was as high as 47%.•TiO2 grains of different sizes were obtained simultaneously inside and outside the support.•The catalytic activity of TiO2 catalyst is 5.4 times that of P25.
•CPPS-2-18 electrode is fabricated by adsorbing the redox mediator(AR18) into the nanopores of CPPS-2 through electrosorption.•AR18 confined into the nanopores can play crucial role on enhancing the ...electrochemical properties of CPPS-2-18.•Due to the confined effect, the shuttle behavior of the ions in the electrolyte is inhabited well.•The electrochemical properties of the electrode are improved by confining AR18 into the nanopores.
The limitation of low energy density of carbon-based supercapacitors can be broken through introducing redox mediators into the electrolyte. Herein, biomass porous carbon CPPS-2 with a high specific surface area of 1649 m2/g was prepared by KOH activation. Capitalizing on the adsorption property of porous carbon, redox mediator, acid red 18 (AR18), was confined into the nanopores of CPPS-2 to fabricate the CPPS-2-18 electrode. After adsorbing 2.72 mg AR18, the specific capacitance of CPPS-2-18 is 568F/g at a current density of 1 A/g in 1 M H2SO4, which is as same as that of CPPS-2 in 1 M H2SO4 + 10 mM AR18, however, the rate performance and coulombic efficiency of CPPS-2-18 are higher than those of CPPS-2. The results reveal that the redox reaction in nanopores of CPPS-2-18 is more reversible than that on the surface of CPPS-2. Meanwhile, the symmetric supercapacitor based on CPPS-2-18 achieves a maximum energy density of 23Wh/kg and power density of 6000 W/kg. Besides, the self-discharging behavior of CPPS-2 is restrained by confining AR18 into the nanopores.
L’arte contemporanea che volge la propria attenzione a indagare la situazione geopolitica del mondo attuale lavora da tempo sui confini visibili e invisibili che separano persone, società e culture. ...La produzione sul tema della reificazione dei confini transnazionali attraverso barriere fisiche (quali i muri) o naturali (quali il mare) è ormai vastissima sia per quantità di lavori prodotti, sia per eterogeneità di forme in cui si esprime. Per la gravità delle conseguenze della loro gestione sulle persone che cercano di attraversarli e per la portata dei discorsi che, inizialmente locali, si rivelano poi potenzialmente universali, due aree rappresentano casi emblematici: il confine tra Messico e Stati Uniti e il bacino del Mediterraneo. L’arte contemporanea si concentra anch’essa su queste aree, con contributi che spesso risuonano con quelli di altre discipline (antropologia, border studies). Facendo riferimento ad alcune opere tra quelle ivi realizzate negli ultimi vent’anni, si individueranno alcune ricorrenze nei discorsi promossi (denuncia delle situazioni contingenti, critica al colonialismo foriero delle discriminazioni attuali, analogie che connettono gli esseri umani al di là della loro variabilità culturale), giungendo a individuare il denominatore comune finale di questi lavori nella volontà di mettere in discussione e abbattere non solo i muri, ma anche i confini, visti come residui di modalità coloniali di relazione tra gli esseri umani ormai non più accettabili.
•Co-MOF derived cobalt phosphide embedded in graphene nanosheets is synthesized.•CoP-NC@GN is used to encapsulate SeS2 for Li/SeS2 batteries.•CoP-NC@GN@SeS2 electrode shows 951.5 and 566.1 mAh g−1 at ...0.02 and 5 A g−1.•580.2 mAh g−1 is attained for CoP-NC@GN@SeS2 electrode after 200 cycles at 2 A g−1.
Selenium sulfide (SeS2) has been considered as a potential cathode for batteries because it has superior conductivity to sulfur and higher theoretical capacity than selenium. Here, the composite of cobalt phosphide embedded in graphene nanosheets (CoP-NC@GN) is synthesized and used to encapsulate SeS2. The fabricated CoP-NC@GN@SeS2 composite is applied for Li/SeS2 batteries. With selenium sulfide content at 52.7%, the CoP-NC@GN@SeS2 composite, when cycled at 2 A g−1, delivers the discharge capacity of 868.6 mAh g−1 and 580.2 mAh g−1 at the 1st and 200th cycle, respectively. The improved performance of CoP-NC@GN@SeS2 is closely related to the elaborately designed structure. The graphene as a substrate ensures the formation of the ZIF-67 and subsequent CoP in nanosize, and allows the maximum exposure of CoP active sites to capture polysulfide/polyselenide intermediates chemically, which is a big plus over the physical adsorption by hollow CoP-NC. The close contact between MOF-derived CoP-NC and graphene nanosheets constructs an excellent consecutive conductive network to accelerate electron conduction and expedite the redox conversion. The synergistic effect enhances cyclic stability and rate performance. This work provides an approach to cathode fabrication for high performance Li/SeS2 batteries.
Technology computer-aided design (TCAD) of semiconductor devices relies on the numerical solution of differential equations in devices. Recent advances in quantum computing provide a new opportunity ...for TCAD simulations to be performed on a quantum computer. Based on a variational quantum algorithm, we develop a quantum-computing-based method to solve quantum confinement problems in semiconductor nanostructures. As the number of numerical discretization grid points for solving the Schrödinger equation increases, the number of qubits needed scales only logarithmically, <inline-formula> <tex-math notation="LaTeX">\sim</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">{\textit{O}}\boldsymbol{}\text{log} {{{\text{(}{\textit{N}}\text{)}}\boldsymbol{}}}</tex-math> </inline-formula>. The method is applied to solve quantum confinement problems at all dimensions, which are related to confinement in a quantum well, semiconductor nanowire, and semiconductor quantum dot structures. The method can treat an anisotropic band structure and electrostatic potential in semiconductor nanostructures. We further show that the design of ansatz plays an important role in the performance of the method in terms of solution accuracy. The quantum-computing-based method can compute the energies and wave functions of both the ground and excited states with high accuracy.
Riassunto L’emergenza Covid-19 e le legislazioni d'urgenza emanate dai governi europei incidono in modo profondo sulla dimensione migratoria contemporanea, così come sulle forme e sui modi di ...studiarla. Il presente contributo, frutto di una “ricerca in quarantena”, si contestualizza nella prima fase dell’irrompere della pandemia in Italia e in Francia (fine febbraio - inizio giugno 2020), segnata dal lockdown nazionale in entrambi i Paesi. L’articolo propone, in primo luogo, una riflessione metodologica relativa al fare etnografia delle migrazioni in tempi pandemici e, di seguito, un’analisi delle conseguenze del Covid-19 sul confine franco-italiano e sull’azione delle reti solidali ai migranti in transito. Il materiale empirico è basato su venti interviste telefoniche semi-strutturate con interlocutori chiave della solidarietà ai migranti sul confine; è costruito inoltre attraverso tecniche di etnografia digitale, quali l’analisi di pagine Facebook e blog dei gruppi intervistati, e su una ricerca emerografica e documentale di carattere locale, nazionale ed internazionale.
Abstract The Covid-19 emergency and the legislation issued by European governments have a deep impact on the contemporary migratory dimension, as well on the forms and ways of studying it. This contribution, the result of a “quarantine research”, is contextualized in the first phase of the outbreak of the pandemic in Italy and France (late February - early June 2020), marked by the national lockdown in both countries. The article proposes, first of all, a methodological reflection about the making of ethnography of migrations in pandemic times and, below, an analysis of the consequences of Covid-19 on the French-Italian border and on the action of solidarity networks with migrants in transit. The empirical material is based on twenty semi-structures telephone interviews with key interlocutors of solidarity with migrants on the border; it is also built through digital ethnographic techniques, such as the analysis of Facebook pages and blogs of the interviewed groups, and on a local, national and international hemerographic and documentary research.
Due to the loosely packed structure, amorphous metal silicate anode could accommodate abundant electrochemical active species, as well as contact tightly with electron donors and electrolyte in ...Lithium-ion batteries (LIBs). However, the bottleneck in this field is how to improve the conductivity and prevent agglomeration of amorphous metal silicate. Herein, we have put forward a novel MnSiO3/RGO hybrid as anode for LIBs, which is realized by in-situ nanospace-confined formation of amorphous MnSiO3 particles rooted in reduced graphene oxide (RGO) nanosheets. Remarkably, the nano-channel of conductive RGO nanosheets provides a confined space for the formation of highly dispersed amorphous MnSiO3 particles, which not only allows for the ultrafast-spreading of Li+ ions and buffers the volume change of anode during lithiation/delithiation processes, but also offers efficient pathway to fast charge transport during the electrochemical process. Benefiting from the reasonable architecture, the MnSiO3/RGO anode delivers a considerable specific capacity of 836.4 mA h g−1 after 200 cycles and also exhibits a remarkable rate performance, which are better than that of previously reported metal silicate-based anode materials in LIBs. Considering the facile fabrication technology and outstanding performance, this work has opened up new opportunities for the development of amorphous metal silicate for high performance LIBs.
•RGO nanosheets provides a confined space for the in-situ formation of amorphous MnSiO3 particles.•Amorphous MnSiO3 particles are refined and encapsulated into the highly conductive RGO nanosheets.•MnSiO3/RGO exhibits the remarkable electrochemical performance among metal silicate-based anode materials in LIBs.
Sorbitol, a product primarily derived from glucose hydrogenation, has extensive applications in the pharmaceutical, chemical and other industries. Amino styrene-co-maleic anhydride polymer ...encapsulated on activated carbon (Ru/ASMA@AC) catalysts were developed for efficient glucose hydrogenation and were prepared and confined Ru by coordination with styrene-co-maleic anhydride polymer (ASMA). Through single-factor experiments, optimal conditions were determined to be 2.5 wt.% ruthenium loading and a catalyst usage of 1.5 g, 20% glucose solution at 130 °C, reaction pressure of 4.0 MPa, and a stirring speed of 600 rpm for 3 h. These conditions achieved a high glucose conversion rate of 99.68% and a sorbitol selectivity of 93.04%. Reaction kinetics testing proved that the hydrogenation of glucose catalyzed by Ru/ASMA@AC was a first-order reaction, with a reaction activation energy of 73.04 kJ/mol. Furthermore, the catalytic performance of the Ru/ASMA@AC and Ru/AC catalysts for glucose hydrogenation were compared and characterized by various detection methods. The Ru/ASMA@AC catalyst exhibited excellent stability after five cycles, whereas the traditional Ru/AC catalyst suffered from a 10% decrease in sorbitol yield after three cycles. These results suggest that the Ru/ASMA@AC catalyst is a more promising candidate for high-concentration glucose hydrogenation due to its high catalytic performance and superior stability.
PDF
