Construction of heterogeneous interfaces for water activation and dissociation to synergistically boost overall water splitting.

Construction of heterogeneous interfaces with dual active components to synergistically promote both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an effective strategy for facilitating electrochemical water splitting, but the appropriate active component regulation via simple synthesis procedures is still challenging. Herein, the Co and Co2Mo3O8 active components are screened to construct effective heterogeneous interfaces and successfully integrated on Ni foam by thermal reduction of cobalt molybdate precursor. And this bifunctional electrode (Co/Co2Mo3O8/NF) required overpotentials of only 164 and 360 mV to drive the 100 mA cm-2 for HER and OER in alkaline media, respectively. Theoretical calculations showed that the electron transfer occurred from Co to Co2Mo3O8 at the interface, then the formed interfacial cobalt atoms with deficient electron were beneficial for water activation, and reduced energy barrier of water dissociation under the synergistic effect of Co2Mo3O8. Notably, the alkaline electrolyzer based on symmetric Co/Co2Mo3O8/NF electrodes generated 100 mA cm-2 at a voltage of only 1.75 V, surpassing commercially available precious-metal Pt/RuO2-based catalysts.

Coupling of Oxygen Vacancies and Heterostructure on Fe3 O4 via an Anion Doping Strategy to Boost Catalytic Activity for Lithium-Sulfur Batteries.

The sluggish reaction kinetics and severe shutting behaviors of sulfur cathodes are the major roadblocks to realizing the practical application of lithium-sulfur (Li-S) batteries and need to be solved through designing/constructing rational sulfur hosts. Herein, an effective alternative material of Fe3 O4- x /FeP in-situ embedded in N-doped carbon-tube (Fe3 O4- x /FeP/NCT) is proposed. In this fabricated heterostructure, NCT skeleton works as a sulfur host provides physical barrier for lithium polysulfides (LiPSs), while Fe3 O4- x /FeP heterostructure with abundant oxygen vacancies provides double active centers to simultaneously accelerate e- /Li+ diffusion/transport kinetics and catalysis for LiPSs. Through the respective advantages, Fe3 O4- x /FeP/NCT exhibits synergy enhancement effect for restraining sulfur dissolution and enhancing its conversion kinetics. Furthermore, the promoted ion diffusion kinetics, enhanced electrical conductivity, and increased active sites of Fe3 O4- x /FeP/NCT are enabled by oxygen vacancies as well as the heterogeneous interfacial contact, which is clearly confirmed by experimental and first-principles calculations. By virtue of these superiorities, the constructed cathode shows excellent long-term cycling stability and a high-rate capability up to 10 C. Specially, a high areal capacity of 7.2 mAh cm-2 is also achieved, holding great promise for utilization in advanced Li-S batteries in the future.

The key role of microscopic structure and graphene sheet-high homogenization in the high rate capability and cycling stability of Ni-Co LDH.

As a typical electrode material in Faraday supercapacitors (FSs), Ni(OH)2 has some intrinsic issues such as low electrical conductivity and structural instability, resulting in its low performance. In view of these issues, we design a multifunctional nanostructure, rigid nanosheet-interlaced structure of Ni-Co LDH/graphene to improve the electrical conductivity and structural stability of Ni(OH)2. Under the high shear applied by a high shear mixer (HSM) and the regulation of polyvinylpyrrolidone (PVP), the designed structure is realized. Benefitting from the well-designed structure and improved electrical conductivity of the graphene sheet-high homogenization, Ni-Co LDH/graphene presents the expected performance. It exhibits a high specific capacity of 1020 C g-1 at a low current density of 2.7 A g-1 and excellent high rate performance (637.5 C g-1 at 62.5 A g-1). The asymmetrical supercapacitors (ASCs) assembled with the composite as the positive material show high energy density (86.5 W h kg-1 at a power density of 695.7 W kg-1). Due to the improved structural stability, the ASCs also exhibit high cycling stability (a capacity retention of 97.8% after 10 000 charge-discharge cycles).

Ultra-high rate capability of the synergistically built dual nanostructure of NiCo2S4/nickel foam as an electrode in supercapacitors.

The microstructure of electrode materials and its synergism with current collectors have been a research focus in the area of Faraday supercapacitors (FSs), while the microstructure of current collectors has been neglected in most cases. To eliminate the electrochemical bottleneck of FSs, the comprehensive consideration on electrodes should simultaneously include both the microstructures of materials and current collectors, and their synergism. In this work, a dual nanostructure of NiCo2S4/nickel foam is built to achieve an electrode with structure-synergistical contribution from materials and current collectors. The as-built electrode presents an ultra-high rate capacity (1223.8 C g-1 at 2.5 A g-1; 53.40% capacity retention at an ultra-high current density of 148.5 A g-1) and excellent cycling stability (94.56% capacity retention after 10 000 charge-discharge cycles). The as-assembled asymmetrical supercapacitors show both high energy and power densities (76.7 W h kg-1 at 425.7 W kg-1; 41.9 W h kg-1 at 10 643.3 W kg-1). These results demonstrate that the dual nanostructure of the electrode is valuable for achieving high performance supercapacitors.

Frogspawn inspired hollow Fe3C@N-C as an efficient sulfur host for high-rate lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries with high theoretical energy densities of ∼2600 W h kg-1 have been recognized as a promising energy storage device. However, the practical application of Li-S batteries is still limited by the cycle stability and rate capability, which is highly relied on the well-designed cathode material. Inspired by the unique structure of frogspawn in Nature, a hollow Fe3C@N-C with frogspawn-like architecture was successfully constructed as a highly efficient sulfur host in this paper. Derived from a Prussian blue self-template, Fe3C@N-C possesses a metal-like Fe3C spawn core and the high conductivity of an N-doped carbon shell. This unique structure enables a large surface area, fast e-/Li+ transport, as well as a large hollow space for the volumetric expansion of the sulfur cathode. Moreover, with the N-doped carbon shell and the polar Fe3C core, the trapping and catalytic conversion of intermediate polysulfides are also facilitated. The strongly coupled interaction of polar Fe3C and polysulfides is confirmed by both theoretical calculations and electrochemical performance. Specifically, the Fe3C@N-C/S electrode presents a high capacity of 1351 mA h g-1 at 0.1C with the Fe3C@N-C as an integrated sulfur host. In particular, the rate capability and cycling stability of the Fe3C@N-C/S electrode is outstanding. It displays a high capacity of 792 mA h g-1 at 5C and a low capacity decay rate of 0.08% per cycle at 0.5C after 400 cycles. This work opens a convenient and economical avenue to design a frogspawn-like hollow metal carbide/carbon as an efficient sulfur host for advanced Li-S batteries.

L-proline-based deep eutectic solvents (DESs) for deep catalytic oxidative desulfurization (ODS) of diesel.

A series of L-proline-based DESs was prepared through an atom economic reaction between L-proline (L-Pro) and four different kinds of organic acids. The DESs were characterized by Fourier transform infrared spectroscopy (FT-IR), H nuclear magnetic resonance (1HNMR), cyclic voltammogram (CV) and the Hammett method. The synthesized DESs were used for the oxidative desulfurization and the L-Pro/p-toluenesultonic acid (L-Pro/p-TsOH) system shows the highest catalytic activity that the removal of dibenzothiophene (DBT) reached 99% at 60°C in 2h, which may involve the dual activation of the L-Pro/p-TsOH. The acidity of four different L-proline-based DESs was measured and the results show that it could not simply conclude that the correlation between the acidity of DESs and desulfurization capability was positive or negative. The electrochemical measurements evidences and recycling experiment indicate a good stability performance of L-Pro/p-TsOH in desulfurization. This work will provide a novel and potential method for the deep oxidation desulfurization.

Layer-by-Layer Assembled C/S Cathode with Trace Binder for Li-S Battery Application.

The C/S cathode with only 0.5 wt % binder, composed with Nafion and PVP, was assembled layer-by-layer for lithium-sulfur battery (Li-S) application. It achieved excellent binding strength and battery performance compared to the cathode with 10 wt % PVDF, which is promising to further increase the practical energy density of Li-S batteries.

Lithium Sulfur Primary Battery with Super High Energy Density: Based on the Cauliflower-like Structured C/S Cathode.

The lithium-sulfur primary batteries, as seldom reported in the previous literatures, were developed in this work. In order to maximize its practical energy density, a novel cauliflower-like hierarchical porous C/S cathode was designed, for facilitating the lithium-ions transport and sulfur accommodation. This kind of cathode could release about 1300 mAh g(-1) (S) capacity at sulfur loading of 6 ~ 14 mg cm(-2), and showed excellent shelf stability during a month test at room temperature. As a result, the assembled Li-S soft package battery achieved an energy density of 504 Wh kg(-1) (654 Wh L(-1)), which was the highest value ever reported to the best of our knowledge. This work might arouse the interests on developing primary Li-S batteries, with great potential for practical application.

Carbon-Free CoO Mesoporous Nanowire Array Cathode for High-Performance Aprotic Li-O2 Batteries.

Although various kinds of catalysts have been developed for aprotic Li-O2 battery application, the carbon-based cathodes are still vulnerable to attacks from the discharge intermediates or products, as well as the accompanying electrolyte decomposition. To ameliorate this problem, the free-standing and carbon-free CoO nanowire array cathode was purposely designed for Li-O2 batteries. The single CoO nanowire formed as a special mesoporous structure, owing even comparable specific surface area and pore volume to the typical Super-P carbon particles. In addition to the highly selective oxygen reduction/evolution reactions catalytic activity of CoO cathodes, both excellent discharge specific capacity and cycling efficiency of Li-O2 batteries were obtained, with 4888 mAh gCoO(-1) and 50 cycles during 500 h period. Owing to the synergistic effect between elaborate porous structure and selective intermediate absorption on CoO crystal, a unique bimodal growth phenomenon of discharge products was occasionally observed, which further offers a novel mechanism to control the formation/decomposition morphology of discharge products in nanoscale. This research work is believed to shed light on the future development of high-performance aprotic Li-O2 batteries.

Steam-etched spherical carbon/sulfur composite with high sulfur capacity and long cycle life for Li/S battery application.

Spherical carbon material with large pore volume and specific area was designed for lithium/sulfur (Li/S) soft package battery cathode with sulfur loading over 75%, exhibiting good capacity output (about 1300 mAh g(-1)-S) and excellent capacity retention (70% after 600 cycles) at 0.1 C. The spherical carbon is prepared via in situ steam etching method, which has the advantages of low cost and easy scale up.

Biomineralization-induced self-assembly of porous hollow carbon nanocapsule monoliths and their application in Li-S batteries.

A carbon capsule monolith possessing ultrasmall hollow nanocores and ultrathin nanoshells with a high surface area and porosity is synthesized by a facile biomineralization-induced self-assembly approach. As a sulfur host in Li-S batteries, it serves as an excellent solvent-restricted, ionic-electronic conductive 'nanoreactor' for sulfur lithiation, enabling superior performance upon cycling.

A hierarchical porous electrode using a micron-sized honeycomb-like carbon material for high capacity lithium-oxygen batteries.

A micron-sized honeycomb-like carbon material (MHC) is prepared in a facile way using nano-CaCO3 as a hard template. A novel electrode for lithium-oxygen batteries is fabricated and displays a superior discharge capacity as high as 5862 mA h g(-1). The higher electrode space utilization is attributed to its hierarchical pore structure, with intrinsic mesopores in the MHC particles for Li2O2 depositions and macropores among them for oxygen transport.

Nitrogen-enriched carbon from melamine resins with superior oxygen reduction reaction activity.

Catalytic carbon: Nitrogen-doped porous carbon (CN(x)) electrocatalysts are derived from inexpensive melamine formaldehyde resins. These potential PEMFC catalysts are synthesized by using a facile method, which yields materials that contain a meso- and macroporous structure. The carbon-based materials display attractive catalytic activity toward ORR and superior stability compared to a commercial Pt-based catalyst.