Iuliia O. Chikunova

Owing to its semiconductor properties, tin(IV) oxide is widely used in gas sensors, photo- and electrocatalysis, fuel cells, electrolyzers etc. In this work, macroporous SnO₂ samples are synthesized by impregnating polystyrene (PS) microspheres with sols containing SnCl₄ and alcohol (96% ethanol, isopropanol, or n-butanol). After impregnation, the composites undergo drying and annealing. After drying, the same samples are washed with water for more complete hydrolysis followed by annealing. The resulting SnO₂ samples are studied by powder X-ray diffraction, X-ray photoelectron spectroscopy, X-ray fluorescence analysis, low-temperature N₂ adsorption (77 K), mercury porosimetry, and scanning electron microscopy. The effect of washing with alcohol and water on the porous characteristics and electrical conductivity of the materials is studied.

A series of tin oxides were synthesized with polystyrene microspheres (250 nm) as the template. It was shown that an increase in the template content led to increasing specific pore volume and to the formation of bimodal pore structure with pores of 9 and 70 nm in diameter. Addition of cetyltrimethylammonium bromide (CTAB) during synthesis led to the formation of friable structures (SEM data), to an increase in the average pore diameter from 19 to 111 nm, and to the formation of macropores of 80–400 nm in size. All materials had similar surface properties and cassiterite structure with 5.9–10.8 nm coherent scattering region (XRD data). Flat-band potentials of the samples were determined and their photoelectrocatalytic properties to oxidation of water and methanol were studied in the potential range of 0.4–1.6 V RHE. It was shown that the sample obtained using CTAB was characterized by lower flat-band potential value, but appeared significantly higher photocurrent in methanol oxidation, which resulted from enhanced macro-meso-porous structure to facilitate methanol pore diffusion.