Evgeny Koshevoy

Sn₃O₄ are promising semiconductor materials due to their visible light absorption ability. In this work, a series of materials, such as SnO₂, Sn₃O₄ and Sn₃O₄/SnO₂ heterostructures, with different phase ratios were prepared using hydrothermal synthesis. The materials were characterized using X-ray diffraction (XRD), Raman and diffuse reflectance spectroscopy (DRS), high resolution transmission electron microscopy (HRTEM), nitrogen adsorption (BET). Flat-band potentials (E_FB) of the samples were determined using the photocurrent onset potential (POP) method. It was shown that the potentials obtained with open circuit potential measurements versus illumination intensity (OCP) likely corresponded to the E_FB of SnO₂ nanoparticles in heterostructures due to interfacial electron transfer from the conducting band of Sn₃O₄ to that of SnO₂. The photo-electrooxidation processes of a series of organic substrates were studied in the potential range of 0.6–1.4 V vs. RHE under irradiation with ultraviolet (λ = 370 nm) and visible (λ = 450 nm) light. The Sn₃O₄ sample showed high activity in the photo-electrooxidation of acetone and formic acid in visible light. The Sn₃O₄/SnO₂ samples exhibited noticeable activity only in the oxidation of formic acid. The presence of the SnO₂ phase in the Sn₃O₄/SnO₂ samples increased the photocurrent values under ultraviolet illumination, but significantly reduced the oxidation efficiency in visible light.

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.