In Situ Constructing Metal-Organic Complex Interface Layer Using Biomolecule Enabling Stabilize Zn Anode.

Aqueous zinc-ion batteries (ZIBs) are considered as a promising candidate for next-generation large-scale energy storage due to their high safety, low cost, and eco-friendliness. Unfortunately, commercialization of ZIBs is severely hindered owing to rampant dendrite growth and detrimental side reactions on the Zn anode. Herein, inspired by the metal-organic complex interphase strategy, the authors apply adenosine triphosphate (ATP) to in situ construct a multifunctional film on the metal Zn surface (marked as ATP@Zn) by a facile etching method. The ATP-induced interfacial layer enhances lipophilicity, promoting uniform Zn2+ flux and further homogenizing Zn deposition. Meanwhile, the functional interlayer improves the anticorrosion ability of the Zn anode, effectively suppressing corrosion and hydrogen evolution. Consequently, the as-prepared ATP@Zn anode in the symmetric cell exhibits eminent plating/stripping reversibility for over 2800 h at 5.0 mA cm-2 and 1 mAh cm-2. Furthermore, the assembled ATP@Zn||MnO2 full cells are investigated to evaluate practical feasibilities. This work provides an efficient and simple strategy to prepare stabilized Zn anode toward high-performance ZIBs.

Organic Species-Intercalated Vanadium Oxide for Sodium-Ion Battery: Mixed-Anion Coordination Effect, Enhanced d-p Orbital Hybridization, and Topotactic Phase Conversion Induced by N-Substitution.

Sodium-ion battery (SIB) is a reasonable alternative to lithium-ion battery (LIB) in the field of grid-scale energy storage systems. Unfortunately, the development of appropriate cathode material is a bottleneck in the field of SIB. In the present work, (p-TQ)-VO, formulated as (p-TQ)0.2V2O5·0.38H2O, was synthesized based on a facile hydrothermal reaction of V2O5 and methylhydroquinone (p-HTQ). And when V2O5 was replaced by VN, (p-TQ)-VN, formulated as (p-TQ)0.22V2(O/N)5, was prepared instead. The (p-TQ)-VO sample displays good electrochemical performance as the SIB cathode. And (p-TQ)-VN shows a much higher capacity at a small current density, and it can maintain structural integrity with partial topotactic phase transformation into NaxV2O5 during the discharge/charge process. A series of characterizations of (p-TQ)-VO and (p-TQ)-VN reveals the successful intercalation of p-TQ into the layered V2O5 with a (001) lattice spacing of 13.7 and 10.7 Å, respectively. In (p-TQ)-VN, partial terminal oxygen (Ot) atoms from the V-O-V layer have been substituted by N atoms, which can boost the orbital hybridization of V 3d and Ot 2p, shorten the V-Ot bonds in the c-axial direction, and elongate the V-O bonds in the ab plane with compressed {VO4N2} octahedra, giving rise to mixed-anion coordination effect. As a result, the enhanced electron densities around the Ot atoms of the V-O-V layer can facilitate the affinity toward the inserted Na+ ions, leading to partial phase conversion into NaNO2/NaNO3. Moreover, density functional density (DFT) calculations reveal that the N-incorporation can improve electron conductivity with richer molecular orbital energy levels, resulting in multistep redox reactions and enhanced capacity.

Phosphorization Engineering on Metal-Organic Frameworks for Quasi-Solid-State Asymmetry Supercapacitors.

Porous carbon and metal oxides/sulfides prepared by using metal-organic frameworks (MOFs) as the precursors have been widely applied to the realm of supercapacitors. However, employing MOF-derived metal phosphides as positive and negative electrode materials for supercapacitors has scarcely been reported thus far. Herein, two types of MOFs are used as the precursors to prepare CoP and FeP4 nanocubes through a two-step controllable heat treatment process. Due to the advantages of composition and structure, the specific capacitances of FeP4 and CoP nanocubes reach 345 and 600 F g-1 at the current density of 1 A g-1 , respectively. Moreover, a quasi-solid-state asymmetric supercapacitor is assembled based on charge matching principle by employing CoP and FeP4 nanocubes as the positive and negative electrodes, respectively, which exhibits a high energy density of 46.38 Wh kg-1 at the power density of 695 W kg-1 . Furthermore, a solar-charging power system is assembled by combining the quasi-solid-state asymmetric supercapacitor and monocrystalline silicon plates, substantiating that the device can power the toy electric fan. This work paves a practical way toward the rational design of quasi-solid-state asymmetry supercapacitors systems affording favorable energy density and long lifespan.

Self-Assembly Hydrothermal Synthesis of Silverton-Type Polyoxometalate-Based Photocatalysts for Enhanced Degradation.

The synthesis of some complex polyoxometalates (POMs) is critical to develop potential photocatalysts with high catalytic activity and selectivity. Here, we address this challenge by a hydrothermal self-assembly route to obtain a novel POM-based Co4W6O21(OH)2·4H2O with a hierarchical microsphere structure. The Co4W6O21(OH)2·4H2O crystallizes in the cubic space group Im3̅ with cell parameters: a = b = c = 12.878 Å, α = ß = γ = 90°, and Z = 4. The structure is further characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectra. After depositing Ag2O nanoparticles on the 3D Co4W6O21(OH)2·4H2O microsphere by photochemical synthesis, the Co4W6O21(OH)2·4H2O/Ag2O heterojunction presents enhanced photocatalytic activity for RhB compared with P25 and pristine Ag2O. Moreover, we confirm the key role of holes for the Co4W6O21(OH)2·4H2O/Ag2O and put forward a possible mechanism for the photocatalytic degradation reaction.

High Energy Capacitors Based on All Metal-Organic Frameworks Derivatives and Solar-Charging Station Application.

High energy and efficient solar charging stations using electrochemical capacitors (ECs) are a promising portable power source for the future. In this work, two kinds of metal-organic framework (MOF) derivatives, NiO/Co3 O4 microcubes and Fe2 O3 microleaves, are prepared via thermal treatment and assembled into electrochemical capacitors, which deliver a relatively high specific energy density of 46 Wh kg-1 at 690 W kg-1 . In addition, a solar-charging power system consisting of the electrochemical capacitors and monocrystalline silicon plates is fabricated and a motor fan or 25 LEDs for 5 and 30 min, respectively, is powered. This work not only adds two novel materials to the growing categories of MOF-derived advanced materials, but also successfully achieves an efficient solar-ECs system for the first time based on all MOF derivatives, which has a certain reference for developing efficient solar-charge systems.

Highly Branched Metal Alloy Networks with Superior Activities for the Methanol Oxidation Reaction.

Three-dimensional (3D) interconnected metal alloy nanostructures possess superior catalytic performance owing to their advantageous characteristics, including improved catalytic activity, corrosion resistance, and stability. Hierarchically structured Ni-Cu alloys composed of 3D network-like microscopic branches with nanoscopic dendritic feelers on each branch were crafted by a facile and efficient hydrogen evolution-assisted electrodeposition approach. They were subsequently exploited for methanol electrooxidation in alkaline media. Among three hierarchically structured Ni-Cu alloys with different Ni/Cu ratios (Ni0.25 Cu0.75 , Ni0.50 Cu0.50 , and Ni0.75 Cu0.25 ), the Ni0.75 Cu0.25 electrode exhibited the fastest electrochemical response and highest electrocatalytic activity toward methanol oxidation. The markedly enhanced performance of Ni0.75 Cu0.25 eletrocatalyst can be attributed to its alloyed structure with the proper Ni/Cu ratio and a large number of active sites on the surface of hierarchical structures.

Quantitative Analysis of the Reduction Kinetics Responsible for the One-Pot Synthesis of Pd-Pt Bimetallic Nanocrystals with Different Structures.

We report a quantitative understanding of the reduction kinetics responsible for the formation of Pd-Pt bimetallic nanocrystals with two distinctive structures. The syntheses involve the use of KBr to manipulate the reaction kinetics by influencing the redox potentials of metal precursor ions via ligand exchange. In the absence of KBr, the ratio between the initial reduction rates of PdCl4(2-) and PtCl4(2-) was about 10.0, leading to the formation of Pd@Pt octahedra with a core-shell structure. In the presence of 63 mM KBr, the products became Pd-Pt alloy nanocrystals. In this case, the ratio between the initial reduction rates of the two precursors dropped to 2.4 because of ligand exchange and, thus, the formation of PdBr4(2-) and PtBr4(2-). The alloy nanocrystals took a cubic shape owing to the selective capping effect of Br(-) ions toward the {100} facets. Relative to the alloy nanocubes, the Pd@Pt core-shell octahedra showed substantial enhancement in both catalytic activity and durability toward the oxygen reduction reaction (ORR). Specifically, the specific (1.51 mA cm(-2)) and mass (1.05 A mg(-1) Pt) activities of the core-shell octahedra were enhanced by about four- and three-fold relative to the alloy nanocubes (0.39 mA cm(-2) and 0.34 A mg(-1) Pt, respectively). Even after 20000 cycles of accelerated durability test, the core-shell octahedra still exhibited a mass activity of 0.68 A mg(-1) Pt, twice that of a pristine commercial Pt/C catalyst.

Hydrogenation of Pt/TiO2{101} nanobelts: a driving force for the improvement of methanol catalysis.

Single-crystalline anatase TiO2 nanobelts with a dominant surface of the {101} facet were hydrogenated and used as substrates of platinum for methanol oxidation reaction (MOR). The hydrogenated TiO2 anatase{101} supporting Pt exhibits a 228% increase of current density for methanol oxidation compared with the same system without hydrogenation under dark conditions. The synergetic interactions of hydrogenated anatase{101} with the Pt cluster were investigated through first principles calculations, and found that the hydrogenation shifts the conduction band minimum to the Fermi level of pristine TiO2, and reduces the activation barrier for methanol dissociation considerably. Thus, this work provides an experimental and theoretical basis for developing non-carbon substrates with high electro-catalytic activity toward MOR.

Vertically aligned cobalt oxide nanowires on graphene networks for high-performance lithium storage.

Despite various electrochemically active materials, such as metals, metal oxides and sulfides, which have been widely utilized for lithium storage, these materials still encounter unsatisfied electrochemical performances including low reversible capacity, slow charge-discharge capability and poor cycle performance. Here, we demonstrate a simple approach to fabricate one-dimensional CoO nanowires vertically aligned on a 3D graphene network (denoted as a 3D CoO/graphene network) via a wet chemistry process. The resulting CoO/graphene network possesses an interconnected graphene network, hierarchical pores and a carpet-like structure. This unique network can (1) facilitate the easy access of the electrolyte, (2) prevent the aggregation of CoO nanowires, (3) accommodate the volume change of CoO during the cycle processes, (4) maintain a high electrical conductivity for the overall electrode and (5) give rise to a high content of CoO in the composite (∼92 wt%). As a result, the 3D CoO/graphene network can be directly used as an anode material without any binder or conductive additives for lithium storage, and it exhibits a high capacity of 857 mAh g(-1), an excellent rate capability and good cycle performance. We believe that such a simple but efficient protocol will provide a new pathway for the fabrication of various 3D metal or metal oxide-graphene networks for wide applications in such fields as energy storage, sensors and catalysts.

Building 3D structures of vanadium pentoxide nanosheets and application as electrodes in supercapacitors.

Various two-dimensional (2D) materials have recently attracted great attention owing to their unique properties and wide application potential in electronics, catalysis, energy storage, and conversion. However, large-scale production of ultrathin sheets and functional nanosheets remains a scientific and engineering challenge. Here we demonstrate an efficient approach for large-scale production of V2O5 nanosheets having a thickness of 4 nm and utilization as building blocks for constructing 3D architectures via a freeze-drying process. The resulting highly flexible V2O5 structures possess a surface area of 133 m(2) g(-1), ultrathin walls, and multilevel pores. Such unique features are favorable for providing easy access of the electrolyte to the structure when they are used as a supercapacitor electrode, and they also provide a large electroactive surface that advantageous in energy storage applications. As a consequence, a high specific capacitance of 451 F g(-1) is achieved in a neutral aqueous Na2SO4 electrolyte as the 3D architectures are utilized for energy storage. Remarkably, the capacitance retention after 4000 cycles is more than 90%, and the energy density is up to 107 W·h·kg(-1) at a high power density of 9.4 kW kg(-1).

NaSn2F5 nanocluster composed of nanoparticles with matched lattices induced by dislocations: Accelerated sodium-ion transport via in situ oxidation in solid-state sodium metal battery.

Na metal batteries using inorganic solid-state electrolytes (SSEs) have attracted extensive attention due to their superior safety and high energy density. However, their development is plagued by the unclear structural/volumetric evolution of SSEs and the corresponding Na+ migration mechanisms. In this work, NaSn2F5 (NSF) clusters are composed of nanoparticles (NPs) with matched lattices induced by dislocations, which can mitigate the volume swelling/shrinkage of the NPs. NSF behaves like a single ion conductor with a high Na+ transference number (tNa+) of 0.79. Specially, the ionic conductivity (σ) of NSF is increased from 7.64 × 10-6 to 5.42 × 10-5 S cm-1 after partial irreversible oxidation of Sn2+ (0.118 Å) â†’ Sn4+ (0.069 Å) with the shrunk ionic radius during the charge process, giving more spaces for Na+ migration. Furthermore, a poly(acrylonitrile)-NaSn2F5-NaPF6 composite polymer electrolyte (NSF CPE) was fabricated with a σ of 4.13 × 10-4 S cm-1 and a tNa+ of 0.60. The NSF CPE-based symmetric cell can operate over 3000 h due to the couplings between the different components in NSF CPE, which is beneficial for ion transfer and the construction of stable solid electrolyte interface. And the quasi-solid-state Na|NSF CPE|Na3V2(PO4)3 full cell displays excellent electrochemical performance.

Direct laser-patterned micro-supercapacitors from paintable MoS2 films.

Micrometer-sized electrochemical capacitors have recently attracted attention due to their possible applications in micro-electronic devices. Here, a new approach to large-scale fabrication of high-capacitance, two-dimensional MoS2 film-based micro-supercapacitors is demonstrated via simple and low-cost spray painting of MoS2 nanosheets on Si/SiO2 chip and subsequent laser patterning. The obtained micro-supercapacitors are well defined by ten interdigitated electrodes (five electrodes per polarity) with 4.5 mm length, 820 µm wide for each electrode, 200 µm spacing between two electrodes and the thickness of electrode is ∼0.45 µm. The optimum MoS2 -based micro-supercapacitor exhibits excellent electrochemical performance for energy storage with aqueous electrolytes, with a high area capacitance of 8 mF cm(-2) (volumetric capacitance of 178 F cm(-3) ) and excellent cyclic performance, superior to reported graphene-based micro-supercapacitors. This strategy could provide a good opportunity to develop various micro-/nanosized energy storage devices to satisfy the requirements of portable, flexible, and transparent micro-electronic devices.

Layered sodium titanate with a matched lattice: a single ion conductor in a solid-state sodium metal battery.

Na metal batteries using solid-state electrolytes (SSEs) have attracted intensive attention due to their superior safety and high energy density. However, the interfacial issue is one of the biggest challenges to their working normally for the achievement of high performance. To address the high SSE/Na interfacial resistance and facilitate Na+ migration, an efficient approach based on a lattice-matching effect is proposed. In this work, we synthesized a sheet-like layered sodium titanate with rich oxygen vacancies formulated as Na0.98Ti1.3O3 (NTO). The NTO sheet behaves like a single ion conductor with a low ion migration activation energy of ∼0.159 eV and a high ion transference number (tNa+) of 0.91, which is due to the weak interactions between the lamellar Na+ ions and unmoved anionic Ti-O-Ti layers in NTO. An NTO composite polymer electrolyte (CPE) was fabricated by combination with poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and NaPF6, and it exhibited a high ion conductivity (σ) of 1.16 × 10-4 S cm-1 with a tNa+ of 0.73. The Na|NTO|Na symmetric cell can work normally in the initial discharge/charge cycles and the Na|NTO CPE|Na cell can endure long-term Na stripping/plating, which is associated with the matched lattice of the Na (110) and NTO (001) facets, d(110) (Na) = d(001) (NTO). Moreover, the Na|NTO CPE|Na3V2(PO4)3 (NVP) full cell presents a high discharge capacity with a good cycling performance. This is probably associated with the intrinsic oxygen vacancies in NTO, which can capture the PF6- anions and accelerate the dissociation of Na+-PF6- pairs in the CPE. And the decreased crystallinity of each component in NTO CPE can promote the migration of Na+ in NTO and along the amorphous PVDF-HFP polymer chain.

Novel Fe2O3 microspheres composed of triangular star-shaped nanorods as an electrode for supercapacitors.

Fe2O3 microspheres with a unique structure were reported for the first time in this article and showed excellent cycling stability as a negative electrode for supercapacitors. A high areal specific capacitance of 1465.26 mF cm-2 was also achieved in sulfur-doped Fe2O3. An asymmetric supercapacitor was assembled demonstrating its potential for practical use.

Single-atom Pt-CeO2/Co3O4 catalyst with ultra-low Pt loading and high performance for toluene removal.

The design and manufacture of high activity and thermal stability catalysts with minimal precious metal loading is essential for deep degradation of volatile organic compounds (VOCs). In this paper, a novel single-atom Pt-CeO2/Co3O4 catalyst with ultra-low Pt loading capacity (0.06 wt%, denoted as 0.06Pt-SA) was fabricated via one-step co-precipitation method. The 0.06Pt-SA exhibited excellent toluene degradation activity of T90 = 169 °C, matched with the nanoparticle Pt-supported CeO2/Co3O4 catalyst with more than six times higher Pt loading (0.41 wt%, denoted as 0.41Pt-NP). Moreover, the ultra-long durability (toluene conversion remains 99% after 120 h stability test) and excellent toluene degradation ability in a wide space speed range of 0.06Pt-SA were superior to that of 0.41Pt-NP catalyst. The excellent performance was derived from the strong metal-support interaction (SMSI) between the single atomic Pt and the carrier, which induced more Pt0 and Ce3+ for oxygen activation and more Co3+ for toluene removal. The in situdiffuse reflectance infrared spectroscopy (DRIFTS) experiments confirmed that the conversion of intermediates was accelerated in the reaction process, thereby promoting the toluene degradation. Our results should inspire the exploitation of noble single-atomic modification strategy for developing the low cost and high performance VOCs catalyst.

In situ electrochemical construction of Co/CoP crystalline-amorphous hetero-phase catalysts for highly efficient electrocatalytic hydrogen evolution.

Herein we develop a facile, one-step electrochemical approach for the in situ construction of a Co/CoP crystalline-amorphous hetero-phase catalyst towards the hydrogen evolution reaction (HER). The unique catalyst demonstrates a low overpotential of 83 mV at 10 mA cm-2 with a small Tafel slope of 55.3 mV dec-1 in 1.0 M KOH. The Co/CoP crystalline-amorphous hetero-phase is highly conducive to regulating the Co-P electronic structure and weakening the H atom adsorption, thus markedly boosting the HER performance. This work offers an innovative strategy to develop a highly efficient transition metal phosphide electrocatalyst with a novel structure.

Improving VOC control strategies in industrial parks based on emission behavior, environmental effects, and health risks: A case study through atmospheric measurement and emission inventory.

Industrial parks have a very important impact on regional economic development, but the extremely complex and relatively concentrated volatile organic compound (VOC) emissions from industrial parks also result in it being difficult to control VOCs. In this study, we took a large integrated industrial park in the upper reaches of the Yangtze River as an example, conducted a 1-year monitoring campaign of ambient air VOCs, and established a speciated VOC emission inventory based on the measured chemical profiles of the key industries. The comprehensive control index (CCI) of 125 VOCs was evaluated using the entropy weighting method based on comprehensive consideration of three aspects, namely, emission behavior, environmental effects, and health risks of VOCs, to identify priority VOC species and their key sources for VOC control in industrial parks. The total estimated VOC emissions in the industrial park in 2019 were 6446.96 t. Steel production, sewage treatment, natural gas chemical industry, pharmaceuticals, and industrial boilers were the main sources of VOC emissions. In terms of VOC components, halocarbons, aromatics, and OVOCs were the largest groups of VOCs emitted from the industrial park, accounting for 73.75 % of the total VOC emissions. Using the entropy weighting method, we evaluated the index weights of five parameters: emissions, ozone formation potential, secondary organic aerosol formation potential, hazard quotient, and lifetime cancer risk. Based on the CCI, five control levels for VOC species were further established. The VOC species in Level I and Level II, which contain species such as naphthalene, 2-chlorotoluene, benzene, acrolein, and chloroform, should be considered as extremely important priority control species. These results serve as a reference for the development of precise control strategies for VOCs in industrial parks.

Manipulating the surface states of BiVO4 through electrochemical reduction for enhanced PEC water oxidation.

Bismuth vanadate (BiVO4) is a prospective candidate for photoelectrochemical (PEC) water oxidation, but its commercial application is limited due to the serious surface charge recombination. In this work, we propose a novel and effective electrochemical reduction strategy combined with co-catalyst modification to manipulate the surface states of the BiVO4 photoanode. Specifically, an ultrathin amorphous structure is formed on the surface of BiVO4 after electrochemical reduction ascribed to the breaking of the surface metal-O bonds. Photoelectrochemical measurements and first-principles calculation show that the electrochemical reduction treatment can effectively reduce the surface energy, thereby passivating the recombined surface states (r-ss) and increasing the mobility of photogenerated holes. In addition, the FeOOH co-catalyst layer further increases the intermediate surface states (i-ss) of BiVO4, stabilizes the surface structure and enhances its PEC performance. Benefiting from the superior charge transfer efficiency and the excellent water oxidation kinetics, the -0.8/BVO/Fe photoanode achieves 2.02 mA cm-2 photocurrent at 1.23 VRHE (2.4 times that of the original BiVO4); meanwhile, the onset potential shifts 90 mV to the cathode. These results provide a new surface engineering tactic to modify the surface states of semiconductor photoanodes for high-efficiency PEC water oxidation.

Nickel hexacyanocobaltate quantum dots embedded in N-doped carbon for aqueous alkaline batteries with ultrahigh durability.

Nickel-cobalt Prussian blue analogues (Ni-Co PBAs) suffer from structural instability in neural and alkaline electrolytes due to the dissolution of metal cations and cyanide anions caused by external H2O attack, resulting in capacity degradation and restricted life span. Herein, in this work, Ni-Co PBA quantum dots embedded in N-doped carbon (CC-Ni-Co PBA) were synthesized via a facile coprecipitation method and in situ polymerization followed by calcination under a nitrogen atmosphere. The obtained electrode provided a high specific capacity of 333.7 C g-1 and still retained 188.8 C g-1 when the current density increased by 40 times. Remarkably, it exhibited outstanding cycling stability with 82% retention of capacity after 10 000 cycles in an aqueous alkaline electrolyte, which benefited from the inner Ni-Co PBA quantum dots that provided a surrounding space and significantly accommodated the volume change during the repeated charge-discharge process, and the outer carbon layer that served as a protective barrier to hinder the Ni-Co PBA from dissolving into the electrolyte, thus realizing the durability of the electrode. Furthermore, an asymmetric alkaline battery device was assembled which achieved a maximum energy density of 33.2 W h kg-1 and a power density of 3.1 kW kg-1. Our work contributed to the development of PBA-based electrode materials with improved cycling stability as battery-type electrodes in aqueous electrolytes.