Kwang Youn Cho

Modified hydrothermal synthesis and characterization of reduced graphene oxide-silver selenide nanocomposites with enhanced reactive oxygen species generation

Abstract A visible-light photocatalyst containing Ag2Se and reduced graphene oxide (RGO) was synthesized by a facile sonochemical-assisted hydrothermal method. X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray analysis, and ultraviolet-visible diffuse reflectance spectroscopy results indicated that the RGO-Ag2Se nanocomposite contained small crystalline Ag2Se nanoparticles dispersed over graphene nanosheets and absorbed visible light. The high crystallinity of the nanoparticles increased photocatalytic activity by facilitating charge transport. N2 adsorption-desorption measurements revealed that the RGO-Ag2Se nanocomposite contained numerous pores with an average diameter of 9 nm, which should allow reactant molecules to readily access the Ag2Se nanoparticles. The RGO-Ag2Se nanocomposite exhibited higher photocatalytic activity than bulk Ag2Se nanoparticles to degrade organic pollutant rhodamine B and industrial dye Texbrite BA-L under visible-light irradiation (γ > 420 nm). The generation of reactive oxygen species in RGO-Ag2Se was evaluated through its ability to oxidize 1,5-diphenylcarbazide to 1,5-diphenylcarbazone. The small size of the Ag2Se nanoparticles in RGO-Ag2Se was related to the use of ultrasonication during their formation, revealing that this approach is attractive to form porous RGO-Ag2Se materials with high photocatalytic activity under visible light.

Novel synthesis of WSe 2 -Graphene-TiO 2 ternary nanocomposite via ultrasonic technics for high photocatalytic reduction of CO 2 into CH 3 OH

In the present work, we report the development of a WSe2-Graphene-TiO2 ternary nanocomposite via ultrasonic techniques and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The band-gap of the WSe2-Graphene-TiO2 was estimated to be about 1.62u202feV which is suitable for photodegradation process under under ultraviolet UV/Visible light irradiation. The photocatalytic potential of nanocomposites is investigated for CO2 reduction to CH3OH. WSe2-G-TiO2 with an optimum loading of graphene of 8u202fwt% showed the high photoactivity, gaining a total CH3OH yield of 6.3262u202fµmolu202fg-1u202fh-1 after 48u202fh. This excellent photoreduction activity is owing to the progressive synergistic relation between WSe2/TiO2 and graphene components in our heterogeneous system.

An eco-friendly synthesized mesoporous-silica particle combined with WSe 2 -graphene-TiO 2 by self-assembled method for photocatalytic dye decomposition and hydrogen production

To address the limitations of titanium dioxide (TiO2) and expand the applicability of the photocatalytic activity of TiO2,WSe2 and silica, an eco-friendly, self-assembled method for combining a silica precursor with a WSe2-graphene-TiO2 composite with cetyltrimethylammonium bromide (CTAB) as surface active agents is proposed. Firstly, for the main target, the photocatalytic degradation of organic dye solutions with different initial pH levels and catalyst dosages under visible light irradiation was surveyed. The as-synthesized sample exhibited highly efficient photocatalytic effects for the treatment of the SO dye solution in the optimal conditions of this study, which included a solution with a pH level of 11 and 0.05-gram dosage of the catalyst. Secondly, previous photocatalytic hydrogen production studies reported markedly better outcomes with SiO2/WSe2-graphene-TiO2 than with the binary WSe2-graphene and ternary WSe2-graphene-TiO2 composites under ambient conditions with and without 20% methanol sacrificing reagents. The SiO2/WSe2-graphene-TiO2 composite is promising to become a potential candidate for photocatalytic performance that performs excellently as well as offer an efficient heterosystem for hydrogen production.