绿色电化学法合成金属有机骨架材料的研究现状

金属有机骨架(Metal-organic frameworks,MOFs)材料是一种由金属离子和有机配体通过配位键组装的无机-有机杂化配合物,在气体分离与储存、吸附、催化、载药以及荧光检测等方面都有广泛应用。在诸多合成MOFs材料的方法中,绿色电化学合成法因能耗低、反应条件温和以及反应时间短等特点而成为研究的热点,但目前该方法仍有许多关键问题亟待解决。本文总结了绿色电化学合成MOFs材料近10年的研究进展,综述了包括阳极合成、阴极合成、间接合成、电镀置换等在内的多种合成方法,并展望了未来的发展前景。

Electrosynthesis of Al/Pb/α-PbO_2 composite inert anode materials

The α-PbO2 deposition layers were prepared on the surface of A1/Pb substrates by constant current electrosynthesis from an alkaline bath, and A1/Pb/α-PbO2 composite inert anode materials were obtained. The effects of the bath composition and bath temperature on the electrosynthesis of α-PbO2 were investigated by means of anodic polarization method, the phase structures and surface microstructures of AI/Pb and α-PbO2 deposition layers were tested by means of X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. The experimental data have shown that the process of α-PbO2 formation have several stages. The appropriate conditions can effectively improve the formation rate of α-PbO2 and avoid the occurrence of oxygen evolution reaction. The α-PbO2 deposition layer obtained in alkaline bath possesses rhombic structure, and it is composed of well developed spherical unit cells.

Ag recovery from copper anode slime by acid leaching at atmospheric pressure to synthesize silver nanoparticles

In this paper, recovery of silver from anode slime of Sarcheshmeh copper complex in lran and subsequent synthesis of silver nanoparticles from leaching solution is investigated. Sarcheshmeh anode slime is mainly consisted ofCu, Ag, Pb and Se. Amount of Ag in the considered anode slime was 5.4% （by weight）. The goal was to recover as much as possible Ag from anode slime at atmospheric pressure to synthesize Ag nanoparticles. Therefore, acid leaching was used for this purpose. The anode slime was leached with sulfuric and nitric acid from room to 90 ~C at different acid concentrations and the run which yielded the most recovery of Ag was selected for Ag nanoparticles synthesis. At this condition, Cu, Pb and Se are lea- ched as well as Ag. To separate Ag from leach solution HCI was added and silver was precipitated as AgCl which were then dissolved by ammonia solution. The Ag nanoparticles are synthesized from this solution by chemical reduction method by aid of sodium borohydride in the presence of PVP and PEG as stabilizers. The synthesized Ag nanoparticles showed a peak of 394 nm in UV-vis spectrum and TEM images showed a rather uniform Ag nanoparticles of 12 nm.

Solution chemistry back‐contact FTO/hematite interface engineering for efficient photocatalytic water oxidation

This work describes a simple yet powerful scalable solution chemistry strategy to create back‐contact rich interfaces between substrates such as commercial transparent conducting fluorine‐doped tin oxide coated glass(FTO)and photoactive thin films such as hematite for low‐cost water oxidation reaction.High‐resolution electron microscopy(SEM,TEM,STEM),atomic force microscopy(AFM),elemental chemical mapping(EELS,EDS)and photoelectrochemical(PEC)investigations reveal that the mechanical stress,lattice mismatch,electron energy barrier,and voids between FTO and hematite at the back‐contact interface as well as short‐circuit and detrimental reaction between FTO and the electrolyte can be alleviated by engineering the chemical composition of the precursor solutions,thus increasing the overall efficiency of these low‐cost photoanodes for water oxidation reaction for a clean and sustainable generation of hydrogen from PEC water‐splitting.These findings are of significant importance to improve the charge collection efficiency by minimizing electron‐hole recombination observed at back‐contact interfaces and grain boundaries in mesoporous electrodes,thus improving the overall efficiency and scalability of low‐cost PEC water splitting devices.

Synthesis and electrochemical performance of TiO_2-B as anode material

TiO2-B was synthesized by solid-state reaction. The structures, surface morphologies and electrochemical performances of TiO2-B were characterized by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and electrochemical measurement, respectively. The effects of calcining temperature, molar ratio of K2O to TiO2 and calcining time on the characteristics of TiO2-B were investigated. The results show that the calcining time exerts a significant influence on the electrochemical performances of TiO2-B. The TiO2-B is obtained with good crystal structure and suitable size by using K2Ti4O9, which is prepared at 950 ℃for 24 h under the condition of x（K2O）/x（TiO2）=1：3.5. The TiO2-B delivers all initial discharge capacity of 231.6 mA.h/g. And the rate caoacitv is 73.2 mA-h/g at 1 675 mA/g, which suggests that TiO2-B is a promising anode material for the lithium ion batteries.

Dissolution-regrowth synthesis of SiO_2 nanoplates and embedment into two carbon shells for enhanced lithium-ion storage

In this work, SiO2 nanoplates with opened macroporous structure on carbon layer （C-mSiO2） have been obtained by dissolving and subsequent ingrowing the outer solid SiO2 layer of the aerosol-based C-SiO2 double-shell hollow spheres. Subsequently, triple-shell C-mSiO2-C hollow spheres were successfully prepared after coating the C- mSiO2 templates by the carbon layer from the carbonization of sucrose. When being applied as the anode material fur lithium-ion batteries, the C-mSiO2-C triple-shell hollow spheres deliver a high capacity of 501 mA. h.g- 1 after 100 cycles at 500 mA.g-1 （based on the total mass of silica and the two carbon shells）, which is higher than those of C-mSiO2 （391 mA.h.g 1） spheres with an outer porous SiO2 layer, C-SiO2-C （370 mA-h.g-1） hollow spheres with a middle solid Si02 layer, and C-SiO2 （319.8 mA·h-g-1） spheres with an outer solid SiO2 layer. In addition, the battery still delivers a high capacity of 403 mA· h· g- 1 at a current density of 1000 mA· g- 1 after 400 cycles. The good electrochemical performance can be attributed to the high surface area （246.7 m2·g- 1 ） and pore volume （0.441 cm3· g-1） of the anode materials, as well as the unique structure of the outer and inner carbon layer which not only enhances electrical conductivity, structural stability, but buffers volume change of the intermediate SiO2 layer during repeated charge-discharge processes. Furthermore, the SiO2 nanoplates with opened macroporous structure facilitate the electrolyte transport and electrochemical reaction.

Facile synthesis of hollow Ti2Nb10O29 microspheres for high-rate anode of Li-ion batteries

Titanium niobium oxides emerge as promising anode materials with potential for applications in lithium ion batteries with high safety and high energy density.However,the innate low electronic conductivity of such a composite oxide seriously limits its practical capacity,which becomes a serious concern especially when a high rate charge/discharge capability is expected.Here,using a modified template-assisted synthesis protocol,which features an in-situ entrapment of both titanium and niobium species during the formation of polymeric microsphere followed by a pyrolysis process,we succeed in preparing hollow microspheres of titanium niobium oxide with high efficiency in structural control.When used as an anode material,the structurally-controlled hollow sample delivers high reversible capacity(103.7 m A h g^(-1)at 50 C)and extraordinary cycling capability especially at high charge/discharge currents(164.7 m A h g^(-1)after 500 cycles at 10 C).

Hierarchically porous carbon/red phosphorus composite for high-capacity sodium-ion battery anode

Red phosphorus has received remarkable attention as a promising anode material for sodium ion batteries(NIBs) due to its high theoretical capacity. However, its practical application has been impeded by its intrinsic low electronic conductivity and large volume variations during sodiation/desodiation process. Here, we design a composite to confine nanosized red phosphorus into the hierarchically porous carbon(HPC) walls by a vaporization-condensation strategy. The mass loading of P in the HPC/P composite is optimized to deliver a reversible specific capacity of 2,202 m Ah/gpbased on the mass of red P(836 m Ah/gcompositebased on the total composite mass), a high capacity retention over 77% after100 cycles, and excellent rate performance of 929 m Ah/gpat 2 C. The hierarchical porous carbon serves as the conductive networks, downsize the red phosphorus to nanoscale, and provide free space to accommodate the large volume expansions. The suppressed mechanical failure of the red phosphorus also enhances the stability of solid-electrolyte interface(SEI) layer, which is confirmed by the microscopy and impedance spectroscopy after the cycling tests. Our studies provide a feasible approach for potentially viable high-capacity NIB anode.

Silicon-based nanosheets synthesized by a topochemical reaction for use as anodes for lithium ion batteries

Silicon is the most promising anode material for the next generation high- performance lithium ion batteries. However, its commercial application is hindered by its poor performance due to the huge volume change during cycling. Although two-dimensional silicon-based materials show significantly improved performance, flexible synthesis of such materials is still a challenge. In this work, silicon-based nanosheets with a multilayer structure are synthesized for the first time by a topochemical reaction. The morphology and oxidation state of these nanosheets can be controlled by appropriate choice of reaction media and oxidants. Benefiting from the hierarchical structure and ultrathin size, when the silicon-based nanosheets are employed as anodes they exhibit a charge （delithiation） capacity of 800 mAh/g after 50 cycles with a maximum coulombic efficiency of 99.4% and good rate performance （647 mAh/g at 1 A/g）. This work demonstrates a novel method for preparing nanosheets not only for lithium ion batteries but also having various potential applications in other fields, such as catalysts, electronics and photonics.

Improved water-splitting performances of CuW_(1-x)Mo_xO_4 photoanodes synthesized by spray pyrolysis

CuW（1-x）MoxO4 solid solution of CuWO4 and CuMoO4, which is a copper-based multi-component oxide semiconductor, possesses much narrower band gap than CuWO4. In theory, it can absorb a larger part of the visible spectrum, widening the use of solar spectroscopy and obtaining a higher photo-to-chemical conversion efficiency. In this study, CuW（1-x）MoxO4 thin-film photoanodes on conducting glass were prepared using a simple and low-cost spray pyrolysis method. The resulting CuW（1-x）MoxO4 photoanodes perform higher photocurrent than CuWO4 photoanodes under AM 1.5 G simulated sunlight illumination（100 m W cm^（-2））in 0.1 mol L^（-1） phosphate buffer at pH 7. Combined with IPCE and Mott-Schottky analysis, the enhancement of the photocurrent is due to the improvement of photon utilization and the increase of carrier concentration with the incorporation of Mo atoms. Moreover, with the optimal Mo/W atomic ratio,the photocurrent density increases obviously from 0.07 to 0.46 m A cm^（-2） at 1.23 V（RHE） bias. In addition, compared with particle-assembled thin-film photoanodes prepared by solidphase reaction and drop-necking treatment, the photoanodes prepared by spray pyrolysis have obvious advantages in terms of reducing resistance and facilitating charge transport.