Synthesis, characterization and photocatalytic activity of Cu-doped Zn/ZnO photocatalyst with carbon modification

Abstract

Herein, we report the preparation of Cu-doped Zn/ZnO composites with carbon modification via a simple replacement-hydrothermal method using Zn powder and CuSO 4 $5H 2 O as raw materials. The as-synthesized composites were characterized by powder X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). The results showed that Cu doping promotes crystal growth of ZnO, inhibits phase transfer of metallic Zn to ZnO, enhances the optical absorption in the visible region and reduces the recombination of photogenerated electrons and holes. Interestingly, CO 2 dissolved in solution was converted to carbon adhered onto the composite surface (supported by the XPS data). The abundant carbon species present on the composite surface is favorable for surface chemical reactions because it can trap or adsorb reactants which facilitate the transfer of reactants to active sites. The photocatalytic efficiency of the as-synthesized catalysts was evaluated by the degradation of anthraquinone dye (reactive brilliant blue KN-R) in solution under sunlight irradiation. The degradation results revealed that the Cu-doped Zn/ZnO composites have better photocatalytic activities than those of ZnO and Zn/ZnO. The enhancement of the photocatalytic activity of the composites can be attributed to the existence of Cu doping, the Zn/ZnO hetero-structure and covered carbon on the surface of the photocatalysts, which causes electrons to be easily excited from the valence band to the conduction band and efficient separation of electron-hole pairs, as well as quick surface reactions in doped ZnO. Furthermore, a possible growth mechanism of the Cu-doped Zn/ZnO composites with carbon modification was proposed.

Structural and optical properties of Ti and Cu co‐doped ZnO thin films for photovoltaic applications of dye sensitized solar cells

“…This is because at this amount (1.5%) of Cu dopant, very few substitutional Zn sites are available. This corroborates with the findings of Wang et al, where they found grain size is reduced when doping large amounts of Cu into ZnO thin films 69,70 . The values of D and δ are shown in Table 1.…”

“…The d-spacing value of (1.5% Cu and 1% Ti) co-doped ZnO thin film decreases slightly, because at this Cu percentage (1.5%), very few interstitial Zn sites are available. 69,70…”

“…This corroborates with the findings of Wang et al, where they found grain size is reduced when doping large amounts of Cu into ZnO thin films. 69,70 The values of D and δ are shown in Table 1.…”

Interplay of Photoabsorption, Electronic Structure, and Recombination Rate of Charge Carriers on Visible Light Driven Photocatalytic Activity of Cu‐ and N‐Doped Ba3V2O8

“…Before the recombination step can take place, the charge carriers must be trapped by either intrinsic defects in the lattice or extrinsic dopants to increase the lifetime of photoinduced electron–hole pairs 21. Since the reduction of Cu 2+ is thermodynamically feasible in the case of Cu 2+ ‐doped Ba 3 V 2 O 8 , it is reasonable to assume that electrons can be trapped by Cu 2+ , which acts as a sink for photogenerated electrons, reducing the rate of recombination with holes 22. As discussed earlier, nitrogen doping endows intrinsic defects such as oxygen vacancies that are shallow traps for the excited electrons, whereas the holes are trapped by the doped nitrogen, leading to the constraint of recombination of photoinduced electron–hole pairs.…”

Photocatalytic Hydrogen Production from Glycerol Aqueous Solution Using Cu-Doped ZnO under Visible Light Irradiation

“…Different papers report the use of Cu-doped ZnO as an effective photocatalytic material [31,40]. However, this photocatalyst was studied mainly for the degradation of organic pollutants from water and wastewater [40][41][42][43]. In the recent years, the effect of Cu ions in ZnO nanorod arrays for photoelectrochemical water splitting under visible light was investigated [44].…”