Comparative study on photocatalytic activity of transition metals (Ag and Ni)-doped ZnO nanomaterials synthesized via sol–gel method

Abstract

Ag and Ni/ZnO photocatalyst nanostructures were successfully synthesized by a sol–gel method. In this work, the photocatalyst sample was systematically studied based on several factors affecting the performance of photocatalyst, which are size, morphology, band gap, textural properties and the number of active sites presence on the surface of the nanocatalyst. X-ray diffraction revealed that Ag/ZnO nanomaterials experienced multiple phases, meanwhile for Ni/ZnO the phase of nanomaterials were pure and single phase for stoichiometry less than 5%. Field emission scanning electron microscope (FESEM) showed almost all of the synthesized nanomaterials possessed a mixture of nanorods and spherical-like shape morphology. The Ag/ZnO showed high photocatalytic activity, producing at least 14th trials of nanocatalyst reusability on degradation of methyl orange under UV irradiation. Interestingly, this phenomenon was not observed in larger surface area of Ni/ZnO nanomaterials which supposedly favour photocatalytic activity, but instead producing poor photocatalytic performance. The main reasons were studied and exposed by temperature-programmed desorption of carbon dioxide (TPD–CO 2 ) which showed that incorporation of Ag into ZnO lattice has enhanced the number of active sites on the surface of the nanocatalyst. Whereas incorporation of Ni in ZnO has lowered the number of active sites with respect to undoped ZnO. Active sites measurement is effective and significant, providing opportunities in developing an intensive study as an additional factor.

Response to Comment on “Improved CO2 Hydrogenation on Ni–ZnO/MCM-41 Catalysts with Cooperative Ni and ZnO Sites”

“…In comparison to the CO 2 -TPD result for sample F, the enhanced CO 2 -TPD signal for sample E at 120 °C indicates the enhanced basicity of Ni cooperated with ZnO at the interface compared to Ni only. − This peak at 120 °C is dominant in the figure, suggesting a significant increase of CO 2 adsorption on the interface after the addition of a small amount of Zn (1 wt % Zn in sample E). The peak at 507 °C is attributed to CO 2 adsorbed on ZnO. − …”

Synthesis of Ni–Ag–ZnO solid solution nanoparticles for photoreduction and antimicrobial applications

“… 24 Whereas, Jeyachitra et al 25 have reported the synthesis of Ni and Ag codoped ZnO NPs for dye degradation applications. Azfar et al 26 have also reported the synthesis of Ni and Ag codoped ZnO NPs by using the sol–gel method. Recently, Sachi et al 27 reported the synthesis of NiAg@ZnO nanocomposites by in situ chemical co-reduction method and their applications in nitro-compounds reduction reactions.…”

Response surface optimization and modeling of caffeine photocatalytic degradation using visible light responsive perovskite structured LaMnO3

“…For more efficient and low-cost utilization photodegradation schemes, the utilization of light in the visible region of the solar spectrum which constitutes about 40-50% of the entire solar spectrum must be considered [17,18]. Some of the methods that have been widely explored to improve the visible light responsiveness of wide-bandgap semiconductors photocatalyst include doping [19], dye sensitization [4,20], and surface property modification [13]. Despite the research efforts been exerted in trying to improve the visible responsiveness of wide-bandgap semiconductor photocatalyst [21].…”

“…In another study, perovskite structured LaMnO3 was utilized to effectively degrade rhodamine B dye [23]. Some of the reports indicate the usefulness of perovskite structured LaMnO3 and its modified forms in the photodegradation of various organic dyes [17][18][19][20][21][22][23]. Given the successes LaMnO3 recorded as a photocatalyst, it is interesting that little work is done on its utilization as an efficient photocatalyst for the degradation and mineralization of recalcitrant emerging pollutants.…”