Metal–Oleate Complex?Derived Bimetallic Oxides Nanoparticles Encapsulated in 3D Graphene Networks as Anodes for Efficient Lithium Storage with Pseudocapacitance

In this manuscript, we have demonstrated the delicate design and synthesis of bimetallic oxides nanoparticles derived from metal–oleate complex embedded in 3D graphene networks(MnO/CoMn_2O_4  GN), as an anode material for lithium ion batteries. The novel synthesis of the MnO/CoMn_2O_4  GN consists of thermal decomposition of metal–oleate complex containing cobalt and manganese metals and oleate ligand, forming bimetallic oxides nanoparticles, followed by a selfassembly route with reduced graphene oxides. The MnO/CoMn_2O_4  GN composite, with a unique architecture of bimetallic oxides nanoparticles encapsulated in 3D graphene networks, rationally integrates several benefits including shortening the di usion path of Li^+ ions, improving electrical conductivity and mitigating volume variation during cycling. Studies show that the electrochemical reaction processes of MnO/Co Mn_2O_4  GN electrodes are dominated by the pseudocapacitive behavior, leading to fast Li^+ charge/discharge reactions. As a result, the MnO/CoMn_2O_4  GN manifests high initial specific capacity, stable cycling performance, and excellent rate capability.

Co/N-C nanotubes with increased coupling sites by space-confined pyrolysis for high electrocatalytic activity

Searching low cost and non-precious metal catalysts for high-performance oxygen reduction reaction is highly desired. Herein, Co nanoparticles embedded in nitrogen-doped carbon(Co/N—C) nanotubes with internal void space are successfully synthesized by space-confined pyrolysis, which effectively improve the cobalt loading content and restrict the encapsulated particles down to nanometer. Different from the typical conformal carbon encapsulation, the resulting Co/N—C nanotubes possess more cobalt nanoparticles embedded in the nanotubes, which can provide more coupling sites and active sites in the oxygen reduction reaction(ORR). Moreover, the one-dimensional and porous structure provides a high surface area and a fast electron transfer pathway for the ORR. And the Co/N—C electrode presents excellent electrocatalytic ORR activity in terms of low onset potential(30 mV lower than that of Pt/C), small Tafel slop(45.5 mV dec^(-1)) and good durability(88.5% retention after 10,000 s).

Pd single atoms cooperate with S vacancies in ZnIn_(2)S_(4) nanosheets for photocatalytic pure-water splitting

Photocatalytic water splitting has emerged as a new frontier for converting solar energy to green H_(2) and value-added chemicals.Nevertheless,great challenges still remain for developing efficient photocatalysts for pure water splitting without sacrificial agents.In this work,we demonstrate that doping hexagonal ZnIn_(2)S_(4)(ZIS) with Pd single atoms(Pd_(0.03)/ZIS) can serve as a highly efficient photocatalyst for pure water splitting to simultaneously produce H_(2) and H_(2)O_(2) without any sacrificial agents.Results from aberration-corrected high-angle annular dark field scanning transmission electron microscopy,X-ray fine spectroscopy,insitu electron paramagnetic resonance and diffuse Fourier transform infrared spectroscopy reveal that doping ZIS with Pd single atoms facilitates the formation of S vacancies(S_(v)),where the photogenerated electrons can transfer to Pd single atoms,as a result of enhanced separation of electron-hole pairs and improved photocatalytic performance.Impressively,Pd_(0.03)/ZIS displays a stoichiometric ratio of H_(2) and H_(2)O_(2) with the productivity of 1,037.9 and 1,021.4μmol g^(-1)h^(-1),respectively,which has largely outperformed pure ZIS and other reported catalysts for pure water splitting.This work provides an efficient photocatalyst for water splitting to produce H_(2) and H_(2)O_(2),which may attract rapid interest in materials science,chemistry,and heterogeneous catalysis.

Antimony oxides-protected ultrathin Ir-Sb nanowires as bifunctional hydrogen electrocatalysts

Developing electrocatalysts with fast kinetics and long-term stability for alkaline hydrogen oxidation reaction(HOR)and hydrogen evolution reaction(HER)is of considerable importance for the industrial production of green and sustainable energy.Here,an ultrathin Ir-Sb nanowires(Ir-Sb NWs)protected by antimony oxides(SbO_(x))was synthesized as an efficient bifunctional catalyst for both HOR and HER under alkaline media.Except from the much higher mass activities of Ir-Sb nanowires than those of Ir nanowires(Ir NWs)and commercial Pt/C,the SbO_(x) protective layer also contributes to the maintenance of morphology and anti-CO poisoning ability,leading to the long-term cycling performance in the presence of CO.Specifically,the Ir-Sb NW/SbO_(x) exhibits the highest catalytic activities,which are about 3.5 and 4.8 times to those of Ir NW/C and commercial Pt/C toward HOR,respectively.This work provides that the ultrathin morphology and H_(2)O-occupied Sb sites can exert the intrinsic high activity of Ir and effectively optimize the absorption of OH*both in alkaline HER/HOR electrolysis.

Modulate the electronic structure of Cu_(7)S_(4)nanosheet on TiO_(2)for enhanced photocatalytic hydrogen evolution

TiO_(2)is a promising photocatalyst due to its high thermodynamic stability and non-toxicity.However,its applications have been still limited because of the high recombination rate of electron-hole pairs.Herein,we show that by combining heterojunction construction and electronic structure regulation,the electron-hole pairs in TiO_(2)can be effectively separated for enhanced photocatalytic hydrogen evolution.The optimized Cu_(7)S_(4)nanosheet decorated TiO_(2)achieves much enhanced H_(2)evolution rate(11.5 mmol·g−1·h−1),which is 13.8 and 4.2 times of that of TiO_(2)and Cu_(7)S_(4)/TiO_(2),respectively.The results of photoluminescence spectroscopy,transient photocurrent spectra,ultraviolet-visible diffuse reflectance spectra,and electrochemical impedance spectroscopy collectively demonstrate that the enhanced photocatalytic performance of Air-Cu_(7)S_(4)/TiO_(2)is attributed to the effective separation of charge carriers and widened photoresponse range.The electron paramagnetic resonance and X-ray photoelectron spectroscopy results indicate that the increase of Cu2+in the Cu_(7)S_(4)nanosheet after calcination can promote the charge transfer.This work provides an effective method to improve the electron migration rate and charge separation of TiO_(2),which holds great significance for being extended to other material systems and beyond.

Suppressing oxygen redox in layered oxide cathode of sodium-ion batteries with ribbon superstructure and solid-solution behavior

Sodium-ion batteries(SIBs)are proved as one of the most acceptable candidates for replacing lithium-ion batteries in some fields by virtue of a similar“rocking chair”mechanism and the abundance of sodium.The voltage,rate performance,and energy density of these batteries are mainly determined by the cath-odes.Hence,a Li-Ni-Co co-substituted P2-Na_(0.67)[Li_(0.1)(Mn_(0.7)Ni_(0.2)Co_(0.1))_(0.9)]O_(2)(NLMNC)with ribbon super-structure is prepared with the aim of multi-ion synergistic modification.Owing to the addition of Ni and Co,the Jahn-Teller distortion of Mn can be suppressed corresponding with the improved structural stability,and a little bit of oxygen redox activities is triggered.When with the substitution of 10%Li,the X-ray diffraction(XRD)peaks of NLMNC show the ribbon superstructure at about 21°and 22°.The smooth charge/discharge profiles of the NLMNC cathode exhibit the solid-solution reaction.In addition,the platform at high voltage disappears corresponding with the existing oxygen redox activities being suppressed which may be related to the ribbon superstructure and the promotion of the Ni redox.Such NLMNC cathode can deliver a reversible discharge capacity of 123.5 mA h g^(-1)at 10 mA g^(-1).Even if the current density increases to 500 mA g^(-1),a reversible discharge capacity of 112.8 mA h g^(-1)still can be ob-tained.The distinguished cycling stability is related to the reversible migration of Li+between the metal oxide layer and the interlayer and low volume change during cycling.It is also needing to be mentioned that the capacity retention of NLMNC cathode is about 94.4%(based on the highest discharge capacity)after 100 cycles.This work presents an effective route to develop high-performance cathodes for SIBs.

钠离子电池Na_(0.62)K_(0.05)Mn_(0.7)Ni_(0.2)Co_(0.1)O_(2)正极材料:钾离子掺杂且{001}面稳定的中空多面体

钠离子电池中,正极材料至关重要,在很大程度上决定了整个电池的能量密度等性能.层状氧化物是钠离子电池中最有潜力的正极材料之一.然而,层状氧化物仍面临着不可逆相变、容量低、空气稳定性差和循环寿命短等缺点,限制了其实际应用.为了解决相关问题,本研究成功制备了中空结构的Na_(0.62)K_(0.05)Mn_(0.7)Ni_(0.2)Co_(0.1)O_(2)多面体正极材料.其中,少量的大尺寸钾离子实现了对材料中相应钠离子的取代;镍离子的较高氧化还原电位使得氧化物正极材料能够在空气中稳定保存.在100 mA g^(-1)电流密度下放电100次后,仍可保持115.0 mA h g^(-1)的放电比容量.在500 mA g^(-1)的较大电流密度下,材料仍然可实现104.1 mA h g^(-1)的较高放电比容量.研究结果表明,充放电过程中,氧化物正极材料的P2到O2的相变得到了有效地抑制.同时钾离子在层间的嵌入掺杂,使得氧化物正极的钠离子层间距增大,提升了钠离子的迁移速率.因此,Na_(0.62)K_(0.05)Mn_(0.7)Ni_(0.2)Co_(0.1)O_(2)应用于钠离子电池正极时展现出较大的吸引力和应用前景.

Oxyvanite V3O5:A new intercalation-type anode for lithium-ion battery

In the present study,V3O5 microcrystals that synthesized via vacuum calcination are employed as anodes for lithium-ion batteries(LIBs)for the first time.Despite the widely observed sluggish reaction kinetics and poor cycling stability in most microsized transition metal oxides,the V3O5 microcrystals exhibit excellent rate capability(specific capacities of 144 and 125 mAh g^−1 are achieved at extremely high current densities of 20 and 50 A g^−1,respectively)and long-term cycling performance(specific capacity of 117 mAh g^−1 is sustained over 2000 cycles at 50 A g^−1).It is ascribed to the three-dimensional open-framework structure of the V3O5 microcrystals as a major factor in dictating the fast reaction kinetics(lithium diffusion coefficient:~10−9 cm^2 s^−1).In addition,significant insight into the reaction mechanism of the V3O5 microcrystals in concomitant its phase evolution are obtained from ex-situ XRD study,revealing that the V3O5 microcrystals undergo intercalation reaction with insignificant structural change in response to lithiation/delithiation.

SbPS_(4):A novel anode for high-performance sodium-ion batteries

With the in-depth research of sodium-ion batteries(SIBs),the development of novel sodium-ion anode material has become a top priority.In this work,tube cluster-shaped SbPS_(4)was synthesized by a high-temperature solid phase reaction.Then the typical short tubular ternary thiophosphate SbPS_(4)compounded with graphene oxide(SbPS_(4)/GO)was successfully synthesized after ultrasonication and freeze-drying.SbPS_(4)shows a high theoretical specific capacity(1335 mAh/g)according to the conversion-alloying dual mechanisms.The unique short tube inserted in the spongy graphene structure of SbPS_(4)/GO results in boosting the Na ions transport and alleviating the huge volume change in the charging and discharging processes,improving the sodium storage performance.Consequently,the tubular SbPS_(4)compounded with 10%GO provides an outstanding capacity of 359.58 mAh/g at 500 mA/g.The result indicates that SbPS_(4)/GO anode has a promising application potential for SIBs.

Vanadium-based metal-organic frameworks and their derivatives for electrochemical energy conversion and storage

With the excessive consumption of nonrenewable resources,the exploration of effective and durable materials is highly sought after in the field of sustainable energy conversion and storage system.In this aspect,metalorganic frameworks(MOFs)are a new class of crystalline porous organicinorganic hybrid materials.MOFs have recently been gaining traction in energy-related fields.Owing to the coordination flexibility and multiple accessible oxidation states of vanadium ions or clusters,vanadium-MOFs(V-MOFs)possess unique structural characteristics and satisfactory electrochemical properties.Furthermore,V-MOFs-derived materials also exhibit superior electrical conductivity and stability when used as electrocatalysts and electrode materials.This review summarizes the research progress of V-MOFs(inclusive of pristine V-MOFs,V/M-MOFs,and POVbased MOFs)and their derivatives(vanadium oxides,carbon-coated vanadium oxide,vanadium phosphate,vanadate,and other vanadium doped nanomaterials)in electrochemical energy conversion(water splitting,oxygen reduction reaction)and energy storage(supercapacitor,rechargeable battery).Future possibilities and challenges for V-MOFs and their derivatives in terms of design and synthesis are discussed.Lastly,their applications in energy-related fields are also highlighted.

层状钒酸钾应用于高性能高温钠离子电池

在大规模储能领域中,高温钠离子电池(SIBs)受到了广泛关注.然而,较低的充放电效率和较差的循环稳定性仍是制约高温钠离子电池发展的主要因素.因此,开发性能优异的电极材料是高温钠离子电池发展的关键.本工作中,我们通过简单的钾离子插入法制备了KV_(3)O_(8)纳米带作为高温钠离子电池的负极材料.在60℃高温下,KV_(3)O_(8)纳米带表现出高的储钠容量(在0.1 A g^(-1)电流密度下,可逆容量为414 mAh g^(-1))、卓越的倍率性能(在20 A g^(-1)的高电流密度下为220 mA h g^(-1))和优异的循环稳定性(10 A g^(-1)的电流密度下循环1000次,容量几乎没有衰减).此外,通过非原位XRD分析发现,KV_(3)O_(8)纳米带的结构在整个充放电过程中未发生明显变化,进一步证实了其优异的稳定性.本研究表明KV_(3)O_(8)纳米带具有成为高温钠离子电池负极材料的潜力.