Transition metal borides (TMBs) are promising catalysts for hydrogen evolution reaction (HER). While the commercially available TMBs indicate poor HER performance due to powder electrode and low activity sites density, optimizing commercial TMBs for better HER performance is urgent. To break through the challenge, a new strategy is proposed to compose integral bulk electrodes with needle surfaces in TMBs. The integral bulk electrodes in TiB2, ZrB2, and HfB2 are formed under high pressure and high temperature (HPHT), and the nanoneedle morphology is constructed by chemical etching. In the three materials, the smallest overpotential is 346 mV at 10 mA cm−2 in the HCl etched bulk TiB2 electrode, which is about 61.9% higher than commercial TiB2 powder. Better performance arises from better conductivity of the integral bulk electrode, and the nano morphology exposes the edge sides of the structure which have high activity site density. This work is significant for developing new kinds of bulk TMBs catalysts.

https://www.mdpi.com/2073-4344/12/2/222/pdf?version=1644991635

Surface Modification towards Integral Bulk Catalysts of Transition Metal Borides for Hydrogen Evolution Reaction

We proposed an efficient method toward the synthesis of higher tungsten boride WB5-x in the vacuumless direct current atmospheric arc discharge plasma. The crystal structure of the synthesized samples of boron-rich tungsten boride was determined using computational techniques, showing a two-phase system. The ab initio calculations of the energies of various structures with similar X-ray diffraction (XRD) patterns allowed us to determine the composition of the formed higher tungsten boride. We determined the optimal parameters of synthesis to obtain samples with 61.5% WB5-x by volume. The transmission electron microscopy measurements showed that 90% of the particles have sizes of up to 100 nm, whereas the rest of them may have sizes from 125 to 225 nm. Our study shows the possibility of using the proposed vacuumless method as an efficient and inexpensive way to synthesize superhard WB5-x without employing resource-consuming vacuum techniques.

Efficient Synthesis of WB5-x-WB2 Powders with Selectivity for WB5-x Content.

The invention discloses a preparation method of CaV2O4. The preparation method of CaV2O4 comprises the steps: mixing vanadium trioxide and calcium chloride dihydrate evenly so as to obtain a mixture,performing cold press forming, performing vacuum sintering on the formed mixture, performing natural cooling at room temperature so as to obtain a sintered material, crushing the sintered bulk material, adding hydrochloric acid with a mass percentage concentration of less than 5% at a liquid-solid ratio of (20:1)-(40:1) by ml/g, performing stirring and dip rinsing at room temperature for 10-60 minutes, performing filtration, water washing and alcohol washing, and performing vacuum drying so as to obtain the CaV2O4 powder. The heat treatment is performed completely in a vacuum system, no hydrogen reduction is adopted for treatment, and therefore safety is ensured during the treatment.

Preparation method of CaV2O4

The invention relates to a preparation method of magnesium metavanadate. The preparation method comprises the following steps that (1) vanadate and water are mixed, and thus a sizing mixture is obtained; (2) magnesium salt and the sizing mixture obtained in the step (1) are mixed, heating for reaction is conducted, and a filter cake and filtrate are obtained after filtering; and (3) evaporative crystallization is conducted, and the magnesium metavanadate and crystallization mother liquor are obtained after solid-liquid separation, wherein the magnesium salt is light magnesium carbonate and/orheavy magnesium carbonate. The purity of the magnesium metavanadate prepared through the preparation method of the magnesium metavanadate reaches up to 99.75%, the utilization rate of the vanadate andthe magnesium salt is high, the utilization rate of the magnesium salt reaches up to 85.7%, energy consumption in the preparation process is low, and industrial application and popularization are facilitated.

Preparation method of magnesium metavanadate

The invention mainly provides a preparation method of a carbon doped CaV2O4 magnetic composite material. The carbon-doped magnetic composite material is mainly composed of carbon and an antiferromagnetic CaV2O4 material. The main method comprises the following steps of: electrolyzing a vanadium-containing raw material and active material additives in a molten salt for a certain time at a certain temperature, collecting electrolysis products at a cathode, and performing post-treatment to obtain the carbon-doped CaV2O4 magnetic material. The molten salt electrolysis process using the vanadium-containing material as a raw material and added with the active material additives is simple in process, safe to operate and environment-friendly; the high-value carbon-doped CaV2O4 magnetic composite material is prepared, the benign combination of conductivity and magnetism of the material can be realized, and the high-value carbon-doped CaV2O4 magnetic composite material has good wave-absorbing performance in Ku band.

Carbon-doped CaV2O4 magnetic composite material and preparation method thereof

The invention relates to a preparation method of CaV2O4. In the preparation method, a two-step solid phase sintering method is adopted for preparing single-phase CaV2O4 polycrystal powder, namely calcium carbonate CaCO3 and vanadium pentoxide V2O5 are taken as raw materials firstly, and a solid phase sintering method is used for preparing CaV2O6, wherein a reaction equation is CaCO3+V2O5->CaV2O6+CO2; and secondly, CaV2O6 is reduced under the hydrogen or CO reducing atmosphere to prepare CaV2O4 polycrystal powder, wherein the reaction equation is CaV2O6+H2->CaV2O4+2H2O.

The forms of boron atoms are many and varied in the structure of transition metal borides (TMBs). The form of boron atoms determines the structure, morphology, and properties of borides. Herein, transition metal monoborides (CrB and WB) with different arrangement of one-dimensional (1D) boron chains were synthesized under high pressures and high temperatures. The 1D boron chains between the interlayers of CrB are parallel to one another, while the 1D boron chains between the interlayers of WB are perpendicular to one another. The morphologies of CrB and WB also show large differences due to the difference in 1D boron chain arrangement. As electrocatalysts for hydrogen evolution reactions (HERs), CrB and WB show good catalysis activity and durability. WB has the smallest overpotential (210 mV) and Tafel slope (90.09 mV dec−1), which is mainly attributed to the intercrossing boron chains improving the electrical properties of WB, as well as the 5d electrons of W being more chemically active. The TOF value of WB is 1.35 s−1, proving that WB has a higher intrinsic catalytic activity during HERs. This work provides a data reference for the development of high-efficiency electrocatalysts.

Constructing 1D Boron Chains in the Structure of Transition Metal Monoborides for Hydrogen Evolution Reactions

The invention discloses a hollow sea urchin type magneto-optic nano-composite medicine carrying system and a preparing method thereof, and belongs to the technical field of nano-composite materials. By adding lauryl sodium sulfate in a solvothermal method, Fe3O4 hollow ball with good water solubility can be prepared and obtained within a short period of time. The hollow sea urchin type nano-composite medicine carrying system wotj an Fe3O4 hollow ball @ ZnO nano-bar structure can be prepared by organically combining with ZnO nano-bars by means of self-assembly. The system has both optical and magnetic properties, and has a large specific surface area, which facilitates medicine loading. Moreover, the preparing method has simple steps, gentle conditions and low cost, and is adapted for large-scale production.

Hougang Fan

Papers

Preparation method of CaV2O4

Constructing 1D Boron Chains in the Structure of Transition Metal Monoborides for Hydrogen Evolution Reactions

Hollow sea urchin type magneto-optic nano-composite medicine carrying system and preparing method thereof