Strengthened Interficial Adhesive Fracture Energy by Young's Modulus Matching Degree Strategy in Carbon-Based HTM Free MAPbI3 Perovskite Solar Cell with Enhanced Mechanical Compatibility.

Carbon-based hole transport layer-free perovskite solar cells (PSCs) based on methylammonium lead triiodide (MAPbI3 ) have become one of the research focus due to low cost, easy preparation, and good optoelectronic properties. However, instability of perovskite under vacancy defects and stress-strain makes it difficult to achieve high-efficiency and stable power output. Here, a soft-structured long-chain 2D pentanamine iodide (abbreviated as "PI") is used to improve perovskite quality and interfacial mechanical compatibility. PI containing CH3 (CH2 )4 NH3 + and I- ions not only passivate defects at grain boundaries, but also effectively alleviate residual stress during high temperature annealing via decreasing Young's modulus of perovskite film. Most importantly, PI effectively increases matching degree of Young's modulus between MAPbI3 (47.1 GPa) and carbon (6.7 GPa), and strengthens adhesive fracture energy (Gc ) between perovskite and carbon, which is helpful for outward release of nascent interfacial stress generated under service conditions. Consequently, photoelectric conversion efficiency (PCE) of optimal device is enhanced from 10.85% to 13.76% and operational stability is also significantly improved. 83.1% output is maintained after aging for 720 h at room temperature and 25-60% relative humidity (RH). This strategy of regulation from chemistry and physics provides a strategy for efficient and stable carbon-based PSCs.

Designing CoHCF@FeHCF Core-Shell Structures to Enhance the Rate Performance and Cycling Stability of Sodium-Ion Batteries.

Prussian blue analogs are well suited for sodium-ion battery cathode materials due to their cheap cost and high theoretical specific capacity. Nax CoFe(CN)6 (CoHCF), one of the PBAs, has poor rate performance and cycling stability, while Nax FeFe(CN)6 (FeHCF) has better rate and cycling performance. The CoHCF@FeHCF core-shell structure is designed with CoHCF as the core material and FeHCF as the shell material to enhance the electrochemical properties. The successfully prepared core-shell structure leads to a significant improvement in the rate performance and cycling stability of the composite compared to the unmodified CoHCF. The composite sample of core-shell structure has a specific capacity of 54.8 mAh g-1 at high magnification of 20 C (1 C = 170 mA g-1 ). In terms of cycle stability, it has a capacity retention rate of 84.1% for 100 cycles at 1 C, and a capacity retention rate of 82.7% for 200 cycles at 5 C. Kinetic analysis shows that the composite sample with the core-shell structure has fast kinetic characteristics, and the surface capacitance occupation ratio and sodium-ion diffusion coefficient are higher than those of the unmodified CoHCF.

What about electrochemical behaviors for aurivillius-phase bismuth tungstate? Capacitive or pseudocapacitive.

Researchers mainly explore the mechanism of pseudocapacitance through studying electrode materials with Faraday pseudocapacitive behavior. Here, we found that Bi2WO6, a typical Aurivillius phase material with pseudo-perovskite structure, showed nearly ideal pseudocapacitive behavior. The cyclic voltammetry curve is approximately rectangular in shape, with no redox peaks, which is similar to that of carbon materials. And the shape of the galvanostatic charge-discharge curve is close to an isosceles triangle. In addition, the kinetic analysis demonstrated that the electrochemical process of the A-Bi2WO6 electrode is dominated by surface processes, not diffusion. The A-Bi2WO6 electrode material presents a great volumetric specific capacitance of 466.5 F cm-3 at 0.5 A g-1. These electrochemical properties confirm that the Bi2WO6 material can serve as an ideal support material to explore pseudocapacitive energy storage. This work also provides guidance for the development of new pseudocapacitive materials.

An Approach to Preparing Ni-P with Different Phases for Use as Supercapacitor Electrode Materials.

Herein, we describe a simple two-step approach to prepare nickel phosphide with different phases, such as Ni2 P and Ni5 P4 , to explain the influence of material microstructure and electrical conductivity on electrochemical performance. In this approach, we first prepared a Ni-P precursor through a ball milling process, then controlled the synthesis of either Ni2 P or Ni5 P4 by the annealing method. The as-prepared Ni2 P and Ni5 P4 are investigated as supercapacitor electrode materials for potential energy storage applications. The Ni2 P exhibits a high specific capacitance of 843.25 F g(-1) , whereas the specific capacitance of Ni5 P4 is 801.5 F g(-1) . Ni2 P possesses better cycle stability and rate capability than Ni5 P4 . In addition, the Fe2 O3 //Ni2 P supercapacitor displays a high energy density of 35.5 Wh kg(-1) at a power density of 400 W kg(-1) and long cycle stability with a specific capacitance retention rate of 96 % after 1000 cycles, whereas the Fe2 O3 //Ni5 P4 supercapacitor exhibits a high energy density of 29.8 Wh kg(-1) at a power density of 400 W kg(-1) and a specific capacitance retention rate of 86 % after 1000 cycles.

Electrode Materials of Cobaltous Fluoride for Supercapacitor and Electrocatalysis Applications.

Herein, CoF2 was synthesized by a solvothermal method. The characterization results of the phase and morphology of the sample show that it was successfully synthesized and its morphology is composed of micron particles with uneven size and shape. The electrochemical test results of SCs in different electrolytes show that CoF2 has electrochemical activity only in alkaline electrolytes. Notably, the electrochemical behavior of CoF2 in LiOH solution is different from that in other alkaline solutions in that charge-discharge curve has a quasi-isosceles triangle shape and the CV curve has no obvious redox peak. That is, it has pseudocapacitance behavior in LiOH. Furthermore, CoF2 as catalyst for HER requires an overpotential of only 168 mV to obtain current density of 10 mA cm-2 and a Tafel slope of 116 mV dec-1 in 1 M KOH solution. This research provides a novel way to explore excellent performance electrode materials for SC and HER.

Selection of oxygen reduction catalysts for secondary tri-electrode zinc-air batteries.

Oxygen reduction reaction (ORR) electrocatalysts, which are highly efficient, low-cost, yet durable, are important for secondary Zn-air cell applications. ORR activities of single and mixed metal oxide and carbon electrocatalysts were studied using rotating disc electrode (RDE) measurements, Tafel slope and Koutecky-Levich plots. It was found that MnOx combined with XC-72R demonstrated high ORR activity and good stability-up to 100 mA cm-2. The performance of the selected ORR electrode and a previously optimised oxygen evolution reaction (OER) electrode was thereafter tested in a custom-built secondary Zn-air cell in a tri-electrode configuration, and the effects of current density, electrolyte molarity, temperature, and oxygen purity on the performance of the ORR and OER electrode were investigated. Finally, the durability of the secondary Zn-air system was assessed, demonstrating energy efficiencies of 58-61% at 20 mA cm-2 over 40 h in 4 M NaOH + 0.3 M ZnO at 333 K.

The cobalt atom protection layers in-situ anchored titanium carbide with controllable interlayer spacing towards stable and fast lithium ions storage.

MXenes are the typical ions insertion-type two-dimensional (2D) nanomaterials, have attracted extensive attention in the Li+ storage field. However, the self-stacking of layered structure and the consumption of electrolyte during the process of charge/discharge will limit the Li+ diffusion dynamics, rate capability and capacity of MXenes. Herein, a Co atom protection layers with electrochemical nonreactivity were anchored on/in the surface/interlayer of titanium carbide (Ti3C2) by in-situ thermal anchoring (x-Co/m-Ti3C2, x  = 45, 65 and 85), which can not only avoid the self-stacking and expand the interlayer spacing of Ti3C2 but also reduce the consumption of Li+ and electrolyte by forming the thin solid electrolyte interphase (SEI) film. The interlayer spacing of Ti3C2 can be expanded from 0.98 to 1.21, 1.36 and 1.33 nm when the anchoring temperatures are 45, 65 and 85 °C due to the pillaring effects of Co atom layers, in where the 65-Co/m-Ti3C2 can achieve the best specific capacity and rate capability attributed to its superior diffusion coefficient of 8.8 × 10-7 cm2 s-1 in Li+ storage process. Furthermore, the 45, 65 and 85-Co/m-Ti3C2 exhibit lower SEI resistances (RSEI) as 1.45 ± 0.01, 1.26 ± 0.01 and 1.83 ± 0.01 Ω compared with the RSEI of Ti3C2 (5.18 ± 0.01 Ω), suggesting the x-Co/m-Ti3C2 demonstrates a thin SEI film due to the protection of Co atom layers. The findings propose a Co atom protection layers with electrochemical nonreactivity, not only giving an approach to expand the interlayer spacing, but also providing a protection strategy for 2D nanomaterials.

Enhancing the Kinetic Process in Biphasic Crystalline NiWO4 /Amorphous Co-B Electrode Materials toward Energy Storage with Ultrahigh Rate Performance.

Here, we report a two-phase crystalline NiWO4 /amorphous Co-B nanocomposite as an electrode material for supercapacitors, which is effectively synthesized via a simple hydrothermal method and chemical precipitation method. The obtained NiWO4 /Co-B exhibits crystal-amorphous contact, which makes it have more active sites than other crystalline-crystalline phase boundaries, thereby enhancing electron transport. The NiWO4 /Co-B electrode with the best mass ratio of crystalline and amorphous exhibits a great specific capacitance and excellent cycle durability. Compared to individual Co-B and NiWO4 , it also shows enhanced rate capability Besides, NiWO4 /Co-B/activated carbon supercapacitor device can provide a good specific capacitance and a maximum energy density of 10.92 Wh kg-1 at 200 W kg-1 . This work provides new insights to develop novel electrode materials for energy storage and conversion.

Modification of ultra-micropore dominated carbon by O/N-containing functional groups grafted for enhanced supercapacitor performances.

In our study, a simple method was employed to prepare ultra-micropore-dominated carbon materials with controllable pore size. A mass of heteroatoms was introduced by surface functional group grafting, resulting in enhanced electrochemical performance: the maximum specific capacity of 327.5 F g-1 was obtained at 0.5 A g-1 in 6 M KOH, while that of un-grafted original ultra-microporous carbon was only 188 F g-1, with long-term cycle stability (90.5% of the initial after 10 000 cycles), and excellent rate performance (over 82% at the current density from 0.5 A g-1 to 10 A g-1). The mechanism behind the improved performance was due to the presence of the introduced functional groups that improved the surface wettability of the material and provided additional redox active sites. Their synergistic effects promoted the enhanced electrochemical performance of the ultra-microporous carbon. This study provides a basis for the study of the energy storage mechanism of ultra-microporous carbon and the grafted modification of carbon materials with heteroatom-containing functional groups.

Realizing high-performance and low-cost lithium-ion capacitor by regulating kinetic matching between ternary nickel cobalt phosphate microspheres anode with ultralong-life and super-rate performance and watermelon peel biomass-derived carbon cathode.

Lithium-ion capacitors (LICs) are emerging as one of the most advanced energy storage devices by combining the virtues of both supercapacitors (SCs) and lithium-ion batteries (LIBs). However, the kinetic and capacity mismatch between anode and cathode is the main obstacle to wide applications of LICs. Therefore, the effective strategy of constructing a high-performance LIC is to improve the rate and cycle performance of the anode and the specific capacity of the cathode. Herein, the nickel cobalt phosphate (NiCoP) microspheres anode is demonstrated with robust structural integrity, high electrical conductivity, and fast kinetic feature. Simultaneously, the watermelon-peel biomass-derived carbon (WPBC) cathode is demonstrated a sustainable synthesis strategy with high specific capacity. As expected, the NiCoP exhibits high specific capacities (567 mAh g-1 at 0.1 A g-1), superior rate performance (300 mAh g-1 at 1A g-1), and excellent cycle stability (58 mAh g-1 at 5 A g-1 after 15,000 cycles). The WPBC possesses a high specific surface area (SSA) of 3303.6 m2 g-1 and a high specific capacity of 226 mAh g-1 at 0.1 A g-1. Encouragingly, the NiCoP//WPBC-6 LIC device can deliver high energy density (ED) of 127.4 ± 3.3 and 67 ± 3.8Wh kg-1 at power density (PD) of 190 and 18240 W kg-1 (76.4% capacity retention after 7000 cycles), respectively.

Crystal Phase-Controlled Synthesis of the CoP@Co2P Heterostructure with 3D Nanowire Networks for High-Performance Li-Ion Capacitor Applications.

The paramount focus in the construction of lithium-ion capacitors (LICs) is the development of anode materials with high reversible capacity and fast kinetics to overcome the mismatch of kinetics and capacity between the anode and cathode. Herein, a strategy is presented for the controllable synthesis of cobalt-based phosphides with various morphologies by adjusting the time of the phosphidation process, including 3D hierarchical needle-stacked diabolo-shaped CoP nanorods, 3D hierarchical stick-stacked diabolo-shaped Co2P nanorods, and 3D hierarchical heterostructure CoP@Co2P nanorods. 3D hierarchical nanostructures and a highly conductive project to accommodate volume changes are rational designs to achieve a robust construction, effective electron-ion transportation, and rapid kinetics characteristics, thus leading to excellent cycling stability and rate performance. Owing to these merits, the 3D hierarchical CoP, Co2P, and CoP@Co2P nanorods demonstrate prominent specific capacities of 573, 609, and 621 mA h g-1 at 0.1 A g-1 over 300 cycles, respectively. In addition, a high-performance CoP@Co2P//AC LIC is successfully constructed, which can achieve high energy densities of 166.2 and 36 W h kg-1 at power densities of 175 and 17524 W kg-1 (83.7% capacity retention after 12000 cycles). Therefore, the controllable synthesis of various simultaneously constructed crystalline phases and morphologies can be used to fabricate other advanced energy storage devices.

Synthesis of polyvalent ion reaction of MoS2/CoS2-RGO anode materials for high-performance sodium-ion batteries and sodium-ion capacitors.

Metal sulfide is the most promising anode material for sodium storage devices due to its high theoretical capacity and low cost. However, the practical application of metal sulfide is largely hindered by huge capacity fading during the sodiation/desodiation process. Here mixed bimetallic sulfides grown on reduced graphene oxide (MoS2/CoS2-RGO) are prepared via a facile hydrothermal method. MoS2/CoS2-RGO displays a unique 2D structure which provides large specific surface area for pseudocapacitive charge storage, polyvalent ion reaction for ultrahigh capacity, and a heterostructure to high Na-ion diffusion rate. The optimized MoS2/CoS2-RGO shows a considerable reversible capacity of 593.6 mA h g-1 at 100 mA g-1 over 50 cycles and a high rate capability of 215.8 mA h g-1 even at a high specific current of 5000 mA g-1. A reaction kinetics and galvanostatic intermittent titration technique analysis indicates that MoS2/CoS2-RGO possesses fast pseudocapacitive charge storage and high Na-ion diffusion rate, benefiting the kinetics balance between anode and cathode. With this special structure, SICs containing the anode deliver a high specific energy of 152.98 W h kg-1 at 562.5 W kg-1. Similarly, the SIB exhibits a good capacities of 64 mA h g-1 at the high rates of 5C over 100 cycles.

Boosting the performance of cobalt molybdate nanorods by introducing nanoflake-like cobalt boride to form a heterostructure for aqueous hybrid supercapacitors.

Binary transition metal oxides have received extensive attention because of their multiple oxidation states. However, due to the inherent vices of poor electronic/ionic conductivities, their practical performance as supercapacitor material is limited. Herein, a cobalt molybdate/cobalt boride (CoMoO4/Co-B) composite is constructed with cobalt boride nanoflake-like as a conductive additive in CoMoO4 nanorods using a facile water bath deposition process and liquid-phase reduction method. The effects of CoMoO4/Co-B mass ratios on its electrochemical performance are investigated. Remarkably, the CoMoO4/Co-B composite obtained at a mass ratio of 2:1 shows highly enhanced electrochemical performance relative to those obtained at other ratios and exhibits an optimum specific capacity of 436 F g-1 at 0.5 A g-1. This kind of composite could also display great rate capacity (294 F g-1 at 10 A g-1) and outstanding long cycle performance (90.5% capacitance retention over 10 000 cycles at 5 A g-1). Also, the asymmetric supercapacitor device is prepared by using CoMoO4/Co-B composite as the anode with the active carbon as the cathode. Such a device demonstrates an outstanding energy density of 23.18 Wh kg-1 and superior long-term stability with 100% initial specific capacity retained after 10,000 cycles. The superior electrochemical properties show that the CoMoO4/Co-B electrode material has tremendous potential in energy storage equipment applications.

Interface Engineered Binary Platinum Free Alloy-based Counter Electrodes with Improved Performance in Dye-Sensitized Solar Cells.

The high cost and platinum dissolution issues of counter electrodes (CEs) are two core problems for the development of dye-sensitized solar cells (DSSCs). In this work, different CEs based on binary alloy Ru81.09Co18.91, Ru80.55Se19.45 and Co20.85Se79.15 nanostructures for DSSCs were successfully synthesized and investigated by a facile and environmentally friendly approach. Here, we found that the Co20.85Se79.15 alloy CE-based device yields the higher photoelectric conversion efficiency of 7.08% compared with that (5.80%) of the DSSC using a pure Pt CE because of the larger number of active sites with improved charge transferability and reduced interface resistance by matching work function with the I3‒/I‒ redox electrolyte. The inexpensive synthesis method, cost-effectiveness and superior catalytic activity of the Co20.85Se79.15 alloy may open up a new avenue for the development of CEs for DSSCs in the near future.

3D Hierarchically Structured CoS Nanosheets: Li+ Storage Mechanism and Application of the High-Performance Lithium-Ion Capacitors.

Lithium-ion capacitors possess excellent power and energy densities, and they can combine both of those advantages from supercapacitors and lithium-ion batteries, leading to novel generation hybrid devices for storing energy. This study synthesized one three-dimensional (3D) hierarchical structure, self-assembled from CoS nanosheets, according to a simple and efficient manner, and can be used as an anode for lithium ion capacitors. This CoS anode, based on a conversion-type Li+ storage mechanism dominated by diffusion control, showed a large reversible capacity, together with excellent stability for cycling. The CoS shows a discharge capacity ≈434 mA h/g at 0.1 A/g. The hybrid lithium-ion capacitor, which had the CoS anode as well as the biochar cathode, exhibits excellent electrochemical performance with ultrahigh energy and power densities of 125.2 Wh/kg and 6400 W/kg, respectively, and an extended cycling life of 81.75% retention after 40 000 cycles. The CoS with self-assembled 3D hierarchical structure in combination with a carbon cathode offers a versatile device for future applications in energy storage.

A facile strategy for the synthesis of three-dimensional heterostructure self-assembled MoSe2 nanosheets and their application as an anode for high-energy lithium-ion hybrid capacitors.

As energy storage devices, lithium-ion hybrid capacitors (LIHCs) are currently favored by researchers, because they combine the high energy density of lithium-ion batteries and the high power density as well as the long cycle life of electric double-layer capacitors. However, the reason that LIHCs are problematic for researchers and cannot be applied practically is the slow dynamic behavior of the battery type anode that leads to low magnification and cycle performance of the anode, furthermore, causing a dynamic imbalance between the Faraday embedded electrode and the capacitive electrode. Hence, it is imperative to find an anode material that can quickly intercalate/de-intercalate lithium. In this study, a novel anode material, MoSe2 nanoflowers, for LIHCs was incorporated through a facile solvothermal technique. The MoSe2 nanoflowers with a small volume change after Li+ insertion, conducive to a rapid kinetic layered heterostructure, result in extraordinary electrochemical performance. The prepared MoSe2 nanoflowers exhibit very good invertible capacity (641.4 mA h g-1 at 0.1 A g-1 after 200 cycles), superior velocity performance (380.3 mA h g-1 at 5 A g-1) and long-term cycling stability (214.6 mA h g-1 even after 1000 cycles at 1 A g-1) as anode materials for LIHCs. Benefiting from the reasonable nanometer size effect, locally fine charge transfers and low energy diffusion barriers, MoSe2 nanoflowers possess high rate pseudocapacitive behavior. In addition, the assembled MoSe2//AC (AC, activated carbon) LIHCs deliver a high energy density (78.75-39.1 W h kg-1) and high-power characteristic (150-3600 W kg-1). Besides, after 5000 cycles, the capacity retention rate is 70.28% under a broad potential window (0.5-3.5 V). This LIHC based on a transition metal selenide as an anode shows great potential for application in the fields of new energy electric vehicles and smart electronic products.

Cascade Reaction of 1,1-Enediamines with 2-Benzylidene-1H-indene-1,3(2H)-diones: Selective Synthesis of Indenodihydropyridine and Indenopyridine Compounds.

A concise and environmentally friendly route for the synthesis of diverse indenodihydropyridines (3) via a cascade reaction of 1,1-eneamines (1) with benzylidene-1H-indene-1,3(2H)-diones (BIDs) (2) in ethanol media was developed. The targeted compounds were efficiently obtained by only filtration without any further post-treatment. In the one-step cascade reaction, C-C and C-N bonds were constructed. In addition, when 1,4-dioxane was used as a solvent and the mixture of 1,1-eneamines (1) was refluxed with benzylidene-1H-indene-1,3(2H)-diones (BIDs) (2) for about 12 h, indenopyridine compounds (4) were produced. Two kinds of indenopyridine derivatives 3-4 resulted from alternative solvents and temperatures. The reaction had the following features: mild temperature, atom economy, high yields, and potential biological activity of the product.

Facile approach to prepare loose-packed NiO nano-flakes materials for supercapacitors.

The nickel oxide nano-flakes materials prepared by a facile approach maintain high power density at high rates of discharge and have excellent cycle life, suggesting their potential application in supercapacitors.

Facile Route to the Synthesis of 1,3-Diazahetero-Cycle-Fused [1,2-a]Quinoline Derivatives via Cascade Reactions.

A one-step protocol without transition-metal catalysts with simple post-treatment for the synthesis of 1,3-diazaheterocycle-fused [1,2-a]quinoline derivatives via the cascade reaction of 2-fluorobenzaldehyde (1) and heterocyclic ketene aminals (2) was developed. In the one-step cascade reaction, C=C and C-N bonds were constructed, and the targeted compound can be efficiently obtained by filtering without column chromatography. This protocol describes a valuable route to concisely and feasibly obtain 1,3-diazaheterocycle-fused [1,2-a]quinoline derivatives. The synthetic methodology is particularly attractive because of the following features: low-cost solvent, mild temperature, atom economy, high yield, and potential biological activity of the product.

Coprecipitation Reaction System Synthesis and Lithium-Ion Capacitor Energy Storage Application of the Porous Structural Bimetallic Sulfide CoMoS4 Nanoparticles.

Lithium-ion capacitors (LICs) are noticed as a new-type of energy storage device with both capacitive mechanism and battery mechanism. The LICs own outstanding power density and energy density. In our work, an LIC was constructed by using a simple method to prepare a bimetallic sulfide of CoMoS4 nanoparticles as the anode and a self-made biochar [fructus cannabis's shells (FCS)] with excellent specific surface area as the cathode. The CoMoS4//FCS LIC demonstrated that the range of energy density is from 10 to 41.9 W h/kg and the range of power density is from 75 to 3000 W/kg in the meantime, and it also demonstrated a remarkable cycling performance with the capacitance retention of 95% after 10 000 cycles of charging-discharging at 1 A/g. The designed CoMoS4//FCS LIC device exhibits a superior electrochemical performance because of the CoMoS4 loose porous structure leading to excellent dynamic performance, which is conducive to the diffusion of electrolyte and lithium ion transport, and good electric double layer performance of biochar with large specific surface area could be achieved. Therefore, this bimetallic sulfide is a promising active material for LICs, which could be applied to electric vehicles in the future.