S. V. Balakhonov

Effect of supercritical drying parameters on the phase composition and morphology of aerogels based on vanadium oxide

Aerogels based on vanadium oxide were obtained by supercritical drying in carbon dioxide (scCO2) and organic solvents (acetone, n-hexane, n-heptane, and n-octane). The performed study allowed us to reveal the effect of experimental parameters (precursor type, type of primary and secondary solvents) on the phase composition and morphology of obtained aerogels. The obtained samples were studied by X-ray diffractometry, scanning electron microscopy, and capillary nitrogen adsorption-desorption (BET) method.

Synthesis and photocatalytic activity of anatase-based aerogels

VxTi1–xO2 (x = 5 and 10 mol %) solid solutions have been synthesized through supercritical drying in isopropanol at t = 250°C and p = 10 MPa. Their physicochemical properties and photocatalytic performance have been compared to those of an earlier synthesized ZnxTi1–xO2 aerogel containing 10 mol % Zn [1]. It has been shown that increasing the vanadium content of VxTi1–xO2 from 5 to 10 mol % leads to a decrease in hydrogen evolution rate in methanol/water splitting reaction under UV irradiation from 190 to 32 µL/(min gcatal), whereas in the case of the anatase-based aerogel solid solution containing 10 mol % Zn an opposite picture is observed: the hydrogen evolution rate in methanol/water splitting reaction under UV irradiation increases sharply to 700 µL/(min gcatal).

Effect of supercritical drying parameters on the electrochemical properties of vanadium oxide-based aerogels

This paper examines the effect of supercritical drying parameters (including the nature of the solvent) on the electrochemical properties of vanadium oxide-based aerogels. It is shown that, among vanadium oxide-based aerogels prepared using different solvents (supercritical CO2, n-hexane, and n-octane), the material obtained in n-hexane is superior in discharge capacity characteristics: its capacity is 350 to 250 mAh/g in the first seven cycles. The aerogel obtained in supercritical CO2 has a far lower capacity: 80–105 mAh/g.

Comparison of the Physicochemical and Electrochemical Properties of Vanadium Oxide-Based Nanomaterials Prepared by Cryochemical Synthesis and Supercritical Drying Technique

Vanadium oxide-based nanomaterials have been prepared by cryochemical synthesis (CCS) and supercritical drying (SCD) in n-hexane and acetone. We have performed the first comparative analysis which demonstrates differences in the physicochemical and electrochemical properties of the products, related to the key features of the effect of the CCS and SCD approaches. The nanomaterials prepared from the same precursor using CCS and SCD (in acetone and n-hexane) have been shown to differ in phase composition and morphology. The oxidizing annealing of the resultant aerogels and cryogel at 500°C in air leads to the formation of only one phase: α-V2O5. In all cases except the aerogel prepared using SCD in n-hexane, the crystalline α-V2O5 has a higher discharge capacity in comparison with the unannealed aerogels and cryogel. The highest discharge capacity among the annealed aerogels is offered by the sample prepared using SCD in acetone (255 mAh/g), and the highest discharge capacity among the unannealed materials is offered by the sample prepared using SCD in n-hexane (280 mAh/g). The samples range in energy density from 110 to 640 Wh/kg. The highest energy density is also offered by the aerogel prepared using SCD in n-hexane.