Abstract
CuS and CuGaS2 heterojunction catalysts were used to improve hydrogen production performance by photo splitting of methanol aqueous solution in the visible region in this study. CuGaS2, which is a chalcogenide structure, can form structural defects to promote separation of electrons and holes and improve visible light absorbing ability. The optimum catalytic activity of CuGaS2 was investigated by varying the heterojunction ratio of CuGaS2 with CuS. Physicochemical properties of CuS, CuGaS2 and CuS@CuGaS2 nanoparticles were confirmed by X-ray diffraction, ultraviolet visible spectroscopy, high-resolution transmission electron microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. Compared with pure CuS, the hydrogen production performance of CuGaS2 doped with Ga dopant was improved by methanol photolysis, and the photoactivity of the heterogeneous CuS@CuGaS2 catalyst was increased remarkably. Moreover, the 0.5CuS@1.5CuGaS2 catalyst produced 3250 μmol of hydrogen through photolysis of aqueous methanol solution under 10 h UV light irradiation. According to the intensity modulated photovoltage spectroscopy (IMVS) results, the high photoactivity of the CuS@CuGaS2 catalyst is attributed to the inhibition of recombination between electron-hole pairs, accelerating electron-transfer by acting as a trap site at the interface between CuGaS2 structural defects and the heterojunction.
Highlights
Copper sulfide (Cu2−x S, 0< x < 1), a non-toxic and conductive chalcogen compound, has been continuously noted for its excellent photoelectric behavior, potential thermal/electrical properties, and unique biomedical properties for decades, and much extensive research on Cu2−x S micro/nano structures is still being actively conducted
The X-ray diffraction diffraction (XRD) patterns (A) and high-resolution TEM (HRTEM) images (B) are shown in Figure 1 to confirm the crystallinity of synthesized CuS, CuGaS2 and heterojunction CuS@CuGaS2 nanoparticles
The XRD pattern of the heterojunction CuS@CuGaS2 nanoparticles was very similar to the XRD pattern of the CuGaS2 corresponding to the shell, but there was a slight difference in the intensity and position of the peaks as the ratio of CuS:CuGaS2 varied
Summary
Copper sulfide (Cu2−x S, 0< x < 1), a non-toxic and conductive chalcogen compound, has been continuously noted for its excellent photoelectric behavior, potential thermal/electrical properties, and unique biomedical properties for decades, and much extensive research on Cu2−x S micro/nano structures is still being actively conducted. There are many applications of Cu2−x S as a photocatalyst, among which Saranya et al suggested that the morphology of CuS was influenced by the reaction time and surfactant, and its photocatalytic activity for decolorization of methylene blue (MB) dye under visible-light irradiation was 87% [12]. The excellent photosensitivity of chalcogen compounds, including Cu2−x S, in multifunctional complexes is broadly applicable to a wide range of photochemical reactions, so research on chalcogen compounds remains of interest. If chalcogen compounds are expected to perform well in the photoreaction for hydrogen production from water decomposition and their photostability is guaranteed for a long time, development of the chalcogen photocatalyst will be quite a desirable area of study for the generation of environmentally friendly energy sources
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