Latest ArticlesLow-cost and efficient oxygen reduction reaction (ORR) electrocatalysts are the key to developing Zn-air batteries for renewable energy storage. Herein, the Mn-N-P doped carbon sphere was prepared through polymerization of hexachlorotripolyphosphazene (HCCP) and phloroglucinol, and then followed the calcination at 900 ℃. Theory calculations demonstrated the introduction of Mn in N-P doped carbon could lower the dissociation barrier of O2 into O* and promote the ORR through a 4e− pathway. The as-prepared catalysts exhibited a half-wave potential of 0.82 V vs. RHE and limiting current density of 5.2 mA/cm2 toward ORR, which was comparable to those of the commercial Pt/C catalysts. In addition, Zn-air batteries with 0.05 Mn-N-P-C catalysts showed a high specific capacity of 830 mAh/gZn and excellent cycle stability. This facile approach demonstrated herein could be a solution to develop optimum non-precious metal catalysts for the application in cathodes of proton exchange membrane fuel cells. This study also provides new insight to design the catalysts of multi-heteroatom coordinated metal in the carbon matrix for both fundamental researches and practical applications.
Thanks to tunable physical and chemical properties, two-dimensional (2D) materials have received intensive interest, endowing their excellent electrocatalytic performances for applications in energy conversion. However, their catalytic activities are largely determined by poor adsorption energy and limited active edge sites. Herein, a one-step electrochemical exfoliation strategy was developed to fabricate 2D Ni-doped MoS2 nanosheets (Ni-EX-MoS2) with a lateral size of ~500 nm and thickness of ~3.5 nm. Profiting from high electrical conductivity and abundant exposing active sites, Ni-EX-MoS2 catalyst displayed an admirable performance for electrochemical hydrogen evolution reaction (HER) with a low overpotential of 145 mV at 10 mA/cm2 as well as a small Tafel slope of 89 mV/dec in alkaline media, which are superior to those of the most reported MoS2-based electrocatalysts. The formed Ni species with tuning electronic structure played a crucial role as primary active center of Ni-EX-MoS2, as well as the forming stable 1T/2H phase MoS2 interface demonstrated a synergistic effect on electrocatalytic HER performance. Further, Ni-EX-MoS2 was employed as a cathode electrode for alkaline Zn-H2O battery, which displayed a high power density of 3.3 mW/cm2 with excellent stability. This work will provide a simple and effective guideline for design of electrochemically exfoliated transition metal-doped MoS2 nanosheets to inspire their practical applications in energy catalytic and storage.
To investigate the reactivity of homoatomic clusters [E9]4− (E = Si-Pb) and intermetalloid clusters [M@E9]−, the reactions of the Zintl anions [Sn9]4− and [Ni@Sn9]4− with the CdMes2 (Mes = Mesitylene) in the presence of 2.2.2-crypt were carried out. Two new compounds [K(2.2.2-crypt)]6[(Sn9)Cd(Sn9)].en (1) and [K(2.2.2-crypt)]6[(Ni@Sn9)Cd(Ni@Sn9)].en (2) were afforded. Both 1 and 2 were characterized by single-crystal X-ray diffraction, energy dispersive X-ray (EDX), and electrospray ionization mass spectrometry (ESI-MS), and can be viewed as two [Sn9]4− or [Ni@Sn9]4− subunits bridged by Cd ion in an η3: η3 coordination mode. Quantum chemical calculations reveal the relationships between the geometries and electronic structures of clusters 2a, [Ni3Ge18]4− and [Cu4@Sn18]4−. Further electron localization technique (AdNDP method) was performed to explain chemical bonding patterns of 1a.
Traditional methods of preparing metal-organic frameworks (MOFs) compounds have the disadvantages such as poor dispersion, inefficient and discontinuous process. In this work, microchannel reactor is used to prepare MOFs-derived zeolite-imidazole material via flash nanoprecipitation to form ZIF-67 + PEI(FNP), which reduces the MOF synthesis time down to millisecond time interval while keeping the synthesized ZIF-67 + PEI(FNP) highly dispersed. The Co@N–C(FNP)catalyst obtained by flash nanoprecipitation and carbonization has a higher Co content and thus more active sites for oxygen reduction reaction than the Co@N–C(DM) catalyst prepared by direct mixing method. Electrochemical tests show that the Co@N–C(FNP) catalyst prepared by this method has excellent oxygen reduction performance, good methanol resistance and high stability. The onset potential and half-wave potential of Co@N–C(FNP) are 0.92 VRHE and 0.83 VRHE, respectively, which are higher than that of Co@N–C(DM) (Eonset = 0.90 VRHE and E1/2 = 0.83 VRHE). Moreover, the Zn-air battery assembled with Co@N–C(FNP) as the cathode catalyst has high open circuit voltage, high power density and large specific capacity. The performance of these batteries has been comparable to that of Pt/C assembled batteries. Density functional theory (DFT) calculations confirm that the Co (220) crystal plane present in Co@N–C(FNP) have stronger adsorption energy than that of Co (111) crystal plane in Co@N–C(DM), leading to better electrocatalytic performance of the former.
Lithium-sulfur batteries (LSBs) are among the most promising series of next-generation high density energy storage systems. However, the problem of "shuttle effect" caused by dissolution and migration of polysulfide intermediates has severely inhibited their practical applications. Herein, TiO2-carbon nanocomposites embedded hierarchical porous carbon (T-hPC) interlayers are fabricated via Ti3C2 MXene assisted phase separation and annealing method. The T-hPC processes micro- to macro-scale multi-pores along with highly adsorptive and catalytic carbon supported TiO2 nanoparticles, which significantly enhances the polysulfides immobilization and improves the redox reaction kinetics when applied as lithium-sulfur battery interlayers. An initial discharge specific capacity of 1551.1 mAh/g and a stable capacity of 893.8 mAh/g after 200 cycles at 0.5 C are obtained, corresponding to a capacity decay rate of only 0.04% per cycle. The investigations in this paper can provide a simple and effective strategy to enhance the electrochemical properties for lithium-sulfur batteries.
A lithium-sulfur (Li-S) system is an important candidate for future lithium-ion system due to its low cost and high specific theoretical capacity (1675 mAh/g, 2600 Wh/kg), which is greatly hindered by the poor conductivity of sulfur, large volume change and dissolution of lithium polysulfides. Two-dimensional (2D) materials with monolayers or few-layers usually have peculiar structures and physical/chemical properties, which can resolve the critical issues in Li-S batteries. Especially, the metal-based 2D nanomaterials, including ferrum, cobalt or other metal-based composites with various anions, can provide high conductivity, large surface area and abundant reaction sites for restraining the diffusion for lithium polysulfides. In this mini-review, we will present an overview of recent developments on metal-based 2D nanomaterials with various anions as the electrode materials for Li-S batteries. Since the main bottleneck for the Li-S system is the shuttle of polysulfides, emphasis is placed on the structure and components, physical/chemical interaction and interaction mechanisms of the 2D materials. Finally, the challenges and prospects of metal-based 2D nanomaterials for Li-S batteries are discussed and proposed.
Herein, phosphorus-mediated sulfur nanoparticles encapsulated in reduced graphene oxide nanosheets (P-SrGO-T) were successfully synthesized as the cathode for sodium ion battery by a ball milling and the following thermal treatment. A series of covalent bonds, such as P–S, C–S–C, C–O–P and C–S–P, are formed in this process, which are in favor of fixing the sulfur and suppressing the parasitic shuttle effect of polysulfide. Benefiting from the graphene sheets and these covalent bonds, a high reversible capacity of 637.4 mAh/g was achieved in P-SrGO-T after 100 cycles at the current density of 0.2 A/g. In addition, P-SrGO-T also delivers a high-rate capacity (330.7 mAh/g at 5 A/g) attributing to low charge transfer resistance and faster ion diffusion kinetic. This work pushes the progress forward in developing phosphosulfide cathode for sodium ion batteries.
Fast-charging is considered to be a key factor in the successful expansion and use of electric vehicles. Current lithium-ion batteries (LIBs) exhibit high energy density, enabling them to be used in electric vehicles (EVs) over long distances, but they take too long to charge. In addition to modifying the electrode and battery structure, the composition of the electrolyte also affects the fast-charging capability of LIBs. This review provides a comprehensive and in-depth overview of the research progress, basic mechanism, scientific challenges and design strategies of the new fast-charging solution system, focusing on the influences that the compositions of liquid and solid electrolytes have on the fast-charging performance of LIBs. Finally, new insights, promising directions and potential solutions for the electrolytes of fast-charging systems are proposed to stimulate further research on revolutionary next-generation fast-charging LIB chemistry.
Chemotherapy is restricted by efficient drug outflow due to the multiple drug resistance (MDR) in heterogenous nature of tumor. Herein, we present a dual-responsive hyaluronic acid (HA) nanocomposite hydrogel that can not only response to the tumor microenvironment but also enhance chemotherapy. This HA hydrogel consists of a core-shell SiO2 (GOD@SiO2-Arg) and mesoporous silica nanoparticles (MSNs) with doxorubicin (DOX) as the cargo (DOX@MSN). It could rapidly release the GOD@SiO2-Arg nanoparticles at the low pH tumor-specific environment due to the cleavage of imine bond. GOD@SiO2-Arg activated by over-expressed glutathione (GSH) in tumor cells releases GOD due to the cleavage of disulfide bonds, which could oxidize glucose to produce hydrogen peroxide (H2O2) for in situ NO generation via reaction between Arg and H2O2. The validity of this study might provide a method to modulate the tumor microenvironment for enhancing chemotherapy.
The five-year survival rate for pancreatic cancer is less than 5%. However, the current clinical multimodal therapy combined with first-line chemotherapy drugs only increases the patient's median survival from 5.0 months to 7.2 months. Consequently, a new strategy of cancer treatments is urgently needed to overcome this high-fatality disease. Through a series of biometric analyses, we found that KRAS is highly expressed in the tumor of pancreatic cancer patients, and this high expression is closely related to the poor prognosis of patients. It shows that inhibiting the expression of KRAS has great potential in gene therapy for pancreatic cancer. Given those above, we have exploited the possibility of targeted delivery of KRAS shRNA with the intelligent and bio-responsive nanomedicine to detect the special oxidative stress microenvironment of cancer cells and realize efficient cancer theranostics. Our observations demonstrate that by designing the smart self-assembled nanocapsules of melanin with fluorescent nanoclusters we can readily achieve the bio-recognition and bioimaging of cancer cells in biological solution or serum. The self-assembled nanocapsules can make a significant bio-response to the oxidative stress microenvironment of cancer cells and generate fluorescent zinc oxide Nanoclusters in situ for targeted cell bioimaging. Moreover, it can also readily facilitate cancer cell suppression through the targeted delivery of KRAS shRNA and low-temperature hyperthermia. This raises the possibility to provide a promising theranostics platform and self-assembled nanomedicine for targeted cancer diagnostics and treatments through special oxidative stress-responsive effects of cancer cells.
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