Leaping Supercapacitor Performance via a Flash-Enabled Graphene Photothermal Coating.

Elevating the working temperature delivers a simple and universal approach to enhance the energy storage performances of supercapacitors owing to the fundamental improvements in ion transportation kinetics. Among all heating methods, introducing green and sustainable photothermal heating on supercapacitors (SCs) is highly desired yet remains an open challenge, especially for developing an efficient and universal photothermal heating strategy that can be generally applied to arbitrary SC devices. Flash-enabled graphene (FG) absorbers are produced through a simple and facile flash reduction process, which can be coated on the surface of any SC devices to lift their working temperature via a photothermal effect, thus, improving their overall performance, including both power and energy densities. With the systematic temperature-dependent investigation and the in-depth numerical simulation of SC performances, an evident enhancement in capacitance up to 65% can be achieved in photothermally enhanced SC coin cell devices with FG photo-absorbers. This simple, practical, and universal enhancement strategy provides a novel insight into boosting SC performances without bringing complexity in electrode fabrication/optimization. Also, it sheds light on the highly efficient utilization of green and renewable photothermal energies for broad application scenarios, especially for energy storage devices.

Efficient Photocatalytic Desulfurization in Air through Improved Photogenerated Carriers Separation in MOF MIL101/Carbon Dots-g-C3N4 Nanocomposites.

The extensive industrial applications of fuel oil, a critical strategic resource, are accompanied by significant environmental and health concerns due to the presence of sulfur-containing compounds in its composition, which result in hazardous combustion waste. Extensive research has been conducted to develop technologies for low-vulcanization fuel production to address this issue. Consequently, the investigation of catalysts for environmentally friendly and safe photocatalytic desulfurization becomes imperative. To that end, we have designed efficient MIL-101(Fe)/CQDs@g-C3N4 (MIL101/CDs-C3N4) Z-scheme heterojunction photocatalysts with high carrier separation and mobility through a thermal polymerization-hydrothermal strategy. The high concentration of photogenerated carriers facilitates the activation of oxygen and H2O2, leading to increased production of ROS (⋅O2 -, ⋅OH, h+), thereby enhancing the photocatalytic desulfurization (PODS). Additionally, DFT (Density functional theory) calculations were utilized to determine the electron migration pathways of the catalysts and adsorption energies of DBT (dibenzothiophene). Moreover, Gibbs free energy calculations indicated that MIL101/CDs-C3N4 exhibited the lowest activation energy for oxygen and H2O2. The mechanism of photocatalytic desulfurization was proposed through a combination of theoretical calculations and experimental studies. This study provides guidance for the development of MOF-based Z-scheme systems and their practical application in desulfurization processes.

Precise Defect Engineering on Graphitic Carbon Nitrides for Boosted Solar H2 Production.

Defect engineering has been regarded as an "all-in-one strategy" to alleviate the insufficient solar utilization in g-C3 N4 . However, without appropriate modification, the defect benefits will be partly offset due to the formation of deep localized defect states and deteriorated surface states, lowering the photocarrier separation efficiency. To this end, the defective g-C3 N4 is designed with both S dopants and N vacancies via a dual-solvent-assisted synthetic approach. The precise defect control is realized by the addition of ethylene glycol (EG) into precursor formation and molten sulfur into the pyrolysis process, which simultaneously induced g-C3N4. with shallow defect states. These shallow defect energy levels can act as a temporary electron reservoir, which are critical to evoke the migrated electrons from CB with a moderate trapping ability, thus suppressing the bulky photocarrier recombination. Additionally, the optimized surface states of DCN-ES are also demonstrated by the highest electron-trapping resistance (Rtrapping ) of 9.56 × 103 Ω cm2 and the slowest decay kinetics of surface carriers (0.057 s-1 ), which guaranteed the smooth surface charge transfer rather than being the recombination sites. As a result, DCN-ES exhibited a superior H2 evolution rate of 4219.9 µmol g-1 h-1 , which is 29.1-fold higher than unmodified g-C3 N4 .

Macromolecules Promoting Robust Zinc Anode by Synergistic Coordination Effect and Charge Redistribution.

Zn dendrite formation is the main obstacle to commercializing aqueous zinc-ion batteries (ZIBs). α-cyclodextrin (α-CD) is proposed as an environmentally friendly macromolecule additive in the ZnSO4 -based electrolyte to obtain stable and reversible Zn anodes. The results show that α-CD molecules' unique 3D structure can effectively regulate the mass transfer of the electrolyte components and isolate the Zn anode from H2 O molecules. The α-CD provides abundant electrons to the Zn (002) crystallographic plane, which induces charge density redistribution. Such an effect relieves the reduction and aggregation of Zn2+ cations while protecting the Zn metal anode from water molecules. Finally, a small amount of α-CD additive (0.01 M) can enhance the performance of Zn significantly in Zn||Cu cells (1980 cycles with 99.45% average CE) and Zn||Zn cells (8000 h ultra-long cycle life). The excellent practical applicability was further verified in Zn||MnO2 cells.

Photoelectrochemical determination of malathion by using CuO modified with a metal-organic framework of type Cu-BTC.

A photoelectrochemical (PEC) sensor was constructed for the detection of non-electroactive malathion. It is based on the use of a hierarchical CuO material derived from a Cu-BTC metal-organic framework (where BTC stands for benzene-1,3,5-tricarboxylic acid). The modified CuO was obtained by calcination of Cu-BTC at a high temperature (300 °C) and possesses a high photocurrent conversion efficiency. Under irradiation with visible light and in the presence of malathion, the formation of the CuO-malathion complex on the CuO gave rise to an increase in steric hindrance. This results in a decrease in photocurrent. This novel PEC detection method has a lower detection limit of 8.6 × 10-11 mol L-1 and a wide linear range (1.0 × 10-10 ~ 1.0 × 10-5 mol L-1). Graphical abstract Schematic presentation of the Cu-BTC MOF derived photoelectrochemical sensor for non-electroactive malathion detection.

Confined Sulfur in 3 D MXene/Reduced Graphene Oxide Hybrid Nanosheets for Lithium-Sulfur Battery.

Three-dimensional metal carbide MXene/reduced graphene oxide hybrid nanosheets are prepared and applied as a cathode host material for lithium-sulfur batteries. The composite cathodes are obtained through a facile and effective two-step liquid-phase impregnation method. Owing to the unique 3 D layer structure and functional 2 D surfaces of MXene and reduced graphene oxide nanosheets for effective trapping of sulfur and lithium polysulfides, the MXene/reduced graphene oxide/sulfur composite cathodes deliver a high initial capacity of 1144.2 mAh g-1 at 0.5 C and a high level of capacity retention of 878.4 mAh g-1 after 300 cycles. It is demonstrated that hybrid metal carbide MXene/reduced graphene oxide nanosheets could be a promising cathode host material for lithium-sulfur batteries.

Mesoporous MnCo2O4 with a flake-like structure as advanced electrode materials for lithium-ion batteries and supercapacitors.

A mesoporous flake-like manganese-cobalt composite oxide (MnCo2O4) is synthesized successfully through the hydrothermal method. The crystalline phase and morphology of the materials are characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller methods. The flake-like MnCo2O4 is evaluated as the anode material for lithium-ion batteries. Owing to its mesoporous nature, it exhibits a high reversible capacity of 1066 mA h g(-1), good rate capability, and superior cycling stability. As an electrode material for supercapacitors, the flake-like MnCo2O4 also demonstrates a high supercapacitance of 1487 F g(-1) at a current density of 1 A g(-1), and an exceptional cycling performance over 2000 charge/discharge cycles.

A microwave synthesis of mesoporous NiCo2O4 nanosheets as electrode materials for lithium-ion batteries and supercapacitors.

A facile microwave method was employed to synthesize NiCo2 O4 nanosheets as electrode materials for lithium-ion batteries and supercapacitors. The structure and morphology of the materials were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller methods. Owing to the porous nanosheet structure, the NiCo2 O4 electrodes exhibited a high reversible capacity of 891 mA h g(-1) at a current density of 100 mA g(-1) , good rate capability and stable cycling performance. When used as electrode materials for supercapacitors, NiCo2 O4 nanosheets demonstrated a specific capacitance of 400 F g(-1) at a current density of 20 A g(-1) and superior cycling stability over 5000 cycles. The excellent electrochemical performance could be ascribed to the thin porous structure of the nanosheets, which provides a high specific surface area to increase the electrode-electrolyte contact area and facilitate rapid ion transport.

Hierarchical mesoporous SnO microspheres as high capacity anode materials for sodium-ion batteries.

Mesoporous SnO microspheres were synthesised by a hydrothermal method using NaSO4 as the morphology directing agent. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) analyses showed that SnO microspheres consist of nanosheets with a thickness of about 20 nm. Each nanosheet contains a mesoporous structure with a pore size of approximately 5 nm. When applied as anode materials in Na-ion batteries, SnO microspheres exhibited high reversible sodium storage capacity, good cyclability and a satisfactory high rate performance. Through ex situ XRD analysis, it was found that Na(+) ions first insert themselves into SnO crystals, and then react with SnO to generate crystalline Sn, followed by Na-Sn alloying with the formation of crystalline NaSn2 phase. During the charge process, there are two slopes corresponding to the de-alloying of Na-Sn compounds and oxidisation of Sn, respectively. The high sodium storage capacity and good electrochemical performance could be ascribed to the unique hierarchical mesoporous architecture of SnO microspheres.

Synthesis of single-crystalline spinel LiMn2 O4 Nanorods for lithium-ion batteries with high rate capability and long cycle life.

The long-standing challenge associated with capacity fading of spinel LiMn2 O4 cathode material for lithium-ion batteries is investigated. Single-crystalline spinel LiMn2 O4 nanorods were successfully synthesized by a template-engaged method. Porous Mn3 O4 nanorods were used as self-sacrificial templates, into which LiOH was infiltrated by a vacuum-assisted impregnation route. When used as cathode materials for lithium-ion batteries, the spinel LiMn2 O4 nanorods exhibited superior long cycle life owing to the one-dimensional nanorod structure, single-crystallinity, and Li-rich effect. LiMn2 O4 nanorods retained 95.6 % of the initial capacity after 1000 cycles at 3C rate. In particular, the nanorod morphology of the spinel LiMn2 O4 was well-preserved after a long-term cycling, suggesting the ultrahigh structural stability of the single crystalline spinel LiMn2 O4 nanorods. This result shows the promising applications of single-crystalline spinel LiMn2 O4 nanorods as cathode materials for lithium-ion batteries with high rate capability and long cycle life.

Synergy of Dendrites-Impeded Atomic Clusters Dissociation and Side Reactions Suppressed Inert Interface Protection for Ultrastable Zn Anode.

The sluggish ions-transfer and inhomogeneous ions-nucleation induce the formation of randomly oriented dendrites on Zn anode, while the chemical instability at anode-electrolyte interface triggers detrimental side reactions. Herein, this report in situ designs a multifunctional hybrid interphase of Bi/Bi2O3, for the first time resulting in a novel synergistic regulation mechanism involving: (i) chemically inert interface protection mechanism suppresses side reactions; and more fantastically, (ii) innovative thermodynamically favorable Zn atomic clusters dissociation mechanism impedes dendrites formation. Assisted by collaborative modulation behavior, the Zn@Bi/Bi2O3 symmetry cell delivers an ultrahigh cumulative plating capacity of 1.88 Ah cm-2 at 5 mA cm-2 and ultralong lifetimes of 300 h even at high current density and depth of discharge (10 mA cm-2, DODZn: 60%). Furthermore, under a low electrolyte-to-capacity ratio (E/C: 45 µL mAh-1) and negative-to-positive capacity ratio (N/P: 6.3), Zn@Bi/Bi2O3||MnO2 full-cell exhibits a superior capacity retention of 86.7% after 500 cycles at 1 A g-1, which outperforms most existing interphases. The scaled-up Zn@Bi/Bi2O3||MnO2 battery module (6 V, 1 Ah), combined with the photovoltaic panel, presents excellent renewable-energy storage ability and long output lifetime (12 h). This work provides a fantastic synergistic mechanism to achieve the ultrastable Zn anode and can be greatly promised to apply it into other metal-based batteries.

The powerful combination of 2D/2D Ni-MOF/carbon nitride for deep desulfurization of thiophene in fuel: Conversion route, DFT calculation, mechanism.

2D/2D Ni-MOF/g-C3N4 nanocomposite was utilized for desulfurization. The multilayer pore structure and high specific surface area of Ni-MOF/g-C3N4 promote the adsorption and conversion of thiophene. In addition, the two-dimensional structure exposes more active centers and shortens photogenerated carrier migration to the material surface distance, it enhances photogenerated charge transfer. The Ni-MOF and g-C3N4 construct a Z-scheme heterojunction structure with tight contact, it effectively enhances the material's photocatalytic redox ability. In the light, the material generates more photocarriers for the production of free radicals including hydroxyl radicals, holes, and superoxide radicals. The higher carrier concentration of Ni-MOF/g-C3N4 promotes the activation and oxidation of thiophene, consequently enhancing the photocatalytic desulfurization capability. The results showed that the conversion of thiophene was 98.82 % in 3 h under visible light irradiation. Radical capture experiments and analysis using electron paramagnetic resonance spectroscopy demonstrated that superoxide radicals, holes, and hydroxyl radicals played crucial roles in PODS (photocatalytic oxidative desulfurization). In addition, DFT (density functional theory) calculations were conducted to determine the paths of electron migration and TH (thiophene) adsorption energy. Finally, a mechanism for photocatalytic desulfurization was proposed based on the comprehensive analysis of theoretical calculations and experimental studies.

Decade Milestone Advancement of Defect-Engineered g-C3N4 for Solar Catalytic Applications.

Over the past decade, graphitic carbon nitride (g-C3N4) has emerged as a universal photocatalyst toward various sustainable carbo-neutral technologies. Despite solar applications discrepancy, g-C3N4 is still confronted with a general fatal issue of insufficient supply of thermodynamically active photocarriers due to its inferior solar harvesting ability and sluggish charge transfer dynamics. Fortunately, this could be significantly alleviated by the "all-in-one" defect engineering strategy, which enables a simultaneous amelioration of both textural uniqueness and intrinsic electronic band structures. To this end, we have summarized an unprecedently comprehensive discussion on defect controls including the vacancy/non-metallic dopant creation with optimized electronic band structure and electronic density, metallic doping with ultra-active coordinated environment (M-Nx, M-C2N2, M-O bonding), functional group grafting with optimized band structure, and promoted crystallinity with extended conjugation π system with weakened interlayered van der Waals interaction. Among them, the defect states induced by various defect types such as N vacancy, P/S/halogen dopants, and cyano group in boosting solar harvesting and accelerating photocarrier transfer have also been emphasized. More importantly, the shallow defect traps identified by femtosecond transient absorption spectra (fs-TAS) have also been highlighted. It is believed that this review would pave the way for future readers with a unique insight into a more precise defective g-C3N4 "customization", motivating more profound thinking and flourishing research outputs on g-C3N4-based photocatalysis.

Single crystalline Na(0.7)MnO2 nanoplates as cathode materials for sodium-ion batteries with enhanced performance.

Single crystalline rhombus-shaped Na(0.7)MnO2 nanoplates have been synthesized by a hydrothermal method. TEM and HRTEM analyses revealed that the Na(0.7)MnO2 single crystals predominantly exposed their (100) crystal plane, which is active for Na(+)-ion insertion and extraction. When applied as cathode materials for sodium-ion batteries, Na(0.7)MnO2 nanoplates exhibited a high reversible capacity of 163 mA h g(-1), a satisfactory cyclability, and a high rate performance. The enhanced electrochemical performance could be ascribed to the predominantly exposed active (100) facet, which could facilitate fast Na(+)-ion insertion/extraction during the discharge and charge process.

Octahedral tin dioxide nanocrystals as high capacity anode materials for Na-ion batteries.

Single crystalline SnO2 nanocrystals (~60 nm in size) with a uniform octahedral shape were synthesised using a hydrothermal method. Their phase and morphology were characterized by XRD and FESEM observation. TEM and HRTEM analyses identified that SnO2 octahedral nanocrystals grow along the [001] direction, consisting of dominantly exposed {221} high energy facets. When applied as anode materials for Na-ion batteries, SnO2 nanocrystals exhibited high reversible sodium storage capacity and excellent cyclability (432 mA h g(-1) after 100 cycles). In particular, SnO2 nanocrystals also demonstrated a good high rate performance. Ex situ TEM analysis revealed the reaction mechanism of SnO2 nanocrystals for reversible Na ion storage. It was found that Na ions first insert into SnO2 crystals at the high voltage plateau (from 3 V to ~0.8 V), and that the exposed (1 × 1) tunnel-structure could facilitate the initial insertion of Na ions. Subsequently, Na ions react with SnO2 to form NaxSn alloys and Na2O in the low voltage range (from ~0.8 V to 0.01 V). The superior cyclability of SnO2 nanocrystals could be mainly ascribed to the reversible Na-Sn alloying and de-alloying reactions. Furthermore, the reduced Na2O "matrix" may help retard the aggregation of tin nanocrystals, leading to an enhanced electrochemical performance.

Metal-Free 2D/2D van der Waals Heterojunction Based on Covalent Organic Frameworks for Highly Efficient Solar Energy Catalysis.

Covalent organic frameworks (COFs) have emerged as a kind of rising star materials in photocatalysis. However, their photocatalytic activities are restricted by the high photogenerated electron-hole pairs recombination rate. Herein, a novel metal-free 2D/2D van der Waals heterojunction, composed of a two-dimensional (2D) COF with ketoenamine linkage (TpPa-1-COF) and 2D defective hexagonal boron nitride (h-BN), is successfully constructed through in situ solvothermal method. Benefitting from the presence of VDW heterojunction, larger contact area and intimate electronic coupling can be formed between the interface of TpPa-1-COF and defective h-BN, which make contributions to promoting charge carriers separation. The introduced defects can also endow the h-BN with porous structure, thus providing more reactive sites. Moreover, the TpPa-1-COF will undergo a structural transformation after being integrated with defective h-BN, which can enlarge the gap between the conduction band position of the h-BN and TpPa-1-COF, and suppress electron backflow, corroborated by experimental and density functional theory calculations results. Accordingly, the resulting porous h-BN/TpPa-1-COF metal-free VDW heterojunction displays outstanding solar energy catalytic activity for water splitting without co-catalysts, and the H2 evolution rate can reach up to 3.15 mmol g-1 h-1, which is about 67 times greater than that of pristine TpPa-1-COF, also surpassing that of state-of-the-art metal-free-based photocatalysts reported to date. In particular, it is the first work for constructing COFs-based heterojunctions with the help of h-BN, which may provide new avenue for designing highly efficient metal-free-based photocatalysts for H2 evolution.

Enhancing the Electrochemical Properties of Nickel-Rich Cathode by Surface Coating with Defect-Rich Strontium Titanate.

Ni-rich layered ternary cathodes (i.e., LiNixCoyMzO2, M = Mn or Al, x + y + z = 1 and x ≥ 0.8) are promising candidates for the power supply of portable electronic devices and electric vehicles. However, the relatively high content of Ni4+ in the charged state shortens their lifespan due to inevitable capacity and voltage deteriorations during cycling. Therefore, the dilemma between high output energy and long cycle life needs to be addressed to facilitate more widespread commercialization of Ni-rich cathodes in modern lithium-ion batteries (LIBs). This work presents a facile surface modification approach with defect-rich strontium titanate (SrTiO3-x) coating on a typical Ni-rich cathode: LiNi0.8Co0.15Al0.05O2 (NCA). The defect-rich SrTiO3-x-modified NCA exhibits enhanced electrochemical performance compared to its pristine counterpart. In particular, the optimized sample delivers a high discharge capacity of ∼170 mA h/g after 200 cycles under 1C with capacity retention over 81.1%. The postmortem analysis provides new insight into the improved electrochemical properties which are ascribed to the SrTiO3-x coating layer. This layer appears to not only alleviate the internal resistance growth, from uncontrollable cathode-electrolyte interface evolution, but also acts as a lithium diffusion channel during prolonged cycling. Therefore, this work offers a feasible strategy to improve the electrochemical performance of layered cathodes with high nickel content for next-generation LIBs.

Dual-modification of Ni-rich cathode materials through strontium titanate coating and thermal treatment.

Ni-rich layered structure ternary oxides, such as LiNi0.8Co0.1Mn0.1O2 (NCM811), are promising cathode materials for high-energy lithium-ion batteries (LIBs). However, a trade-off between high capacity and long cycle life still obstructs the commercialization of Ni-rich cathodes in modern LIBs. Herein, a facile dual modification approach for improving the electrochemical performance of NCM811 was enabled by a typical perovskite oxide: strontium titanate (SrTiO3). With a suitable thermal treatment, the modified cathode exhibited an outstanding electrochemical performance that could deliver a high discharge capacity of 188.5 mAh/g after 200 cycles under 1C with a capacity retention of 90%. The SrTiO3 (STO) protective layer can effectively suppress the side reaction between the NCM811 and the electrolyte. In the meantime, the pillar effect provided by interfacial Ti doping could effectively reduce the Li+/Ni2+ mixing ratio on the NCM811 surface and offer more efficient Li+ migration between the cathode and the coating layer after post-thermal treatment (≥600 °C). This dual modification strategy not only significantly improves the structural stability of Ni-rich layered structure but also enhances the electrochemical kinetics via increasing diffusion rate of Li+. The electrochemical measurement results further disclosed that the 3 wt% STO coated NCM811 with 600 °C annealing exhibits the best performance compared with other control samples, suggesting an appropriate temperature range for STO coated NCM811 cathode is critical for maintaining a stable structure for the whole system. This work may offer an effective option to enhance the electrochemical performance of Ni-rich cathodes for high-performance LIBs.

Mesoporous nickel oxide nanowires: hydrothermal synthesis, characterisation and applications for lithium-ion batteries and supercapacitors with superior performance.

Mesoporous nickel oxide nanowires were synthesized by a hydrothermal reaction and subsequent annealing at 400 °C. The porous one-dimensional nanostructures were analysed by field-emission SEM, high-resolution TEM and N(2) adsorption/desorption isotherm measurements. When applied as the anode material in lithium-ion batteries, the as-prepared mesoporous nickel oxide nanowires demonstrated outstanding electrochemical performance with high lithium storage capacity, satisfactory cyclability and an excellent rate capacity. They also exhibited a high specific capacitance of 348 F g(-1) as electrodes in supercapacitors.

Polyhedral magnetite nanocrystals with multiple facets: facile synthesis, structural modelling, magnetic properties and application for high capacity lithium storage.

Polyhedral magnetite nanocrystals with multiple facets were synthesised by a low temperature hydrothermal method. Atomistic simulation and calculations on surface attachment energy successfully predicted the polyhedral structure of magnetite nanocrystals with multiple facets. X-ray diffraction, field emission scanning electron microscopy, and high resolution transmission microscopy confirmed the crystal structure of magnetite, which is consistent with the theoretical modelling. The magnetic property measurements show the superspin glass state of the polyhedral nanocrystals, which could originate from the nanometer size of individual single crystals. When applied as an anode material in lithium ion cells, magnetite nanocrystals demonstrated an outstanding electrochemical performance with a high lithium storage capacity, a satisfactory cyclability, and an excellent high rate capacity.