Enhanced photocatalytic activity of ZnO–NiO nanocomposites synthesized through a facile sonochemical route

Abstract

Formation of heterostructures with p-type oxides such as NiO and CuO is one of the effective methods for improving the photocatalytic performance of ZnO. Such systems are often synthesized through template-based growth techniques that involve many steps. We have prepared ZnO-NiO composites through a facile, template-free, low-temperature sonochemical route. High-resolution transmission electron microscopy analysis indicates the formation of ZnO-NiO heterostructures. Photocatalytic activity of ZnO-NiO nanocomposites in the decomposition of methylene blue dye under solar irradiation is found to be much larger than that of both pure ZnO (1.26 × 10 −2 min −1 ) and NiO (0.31 × 10 −2 min −1 ) establishing synergistic effects. The rate constant increases with increase in the percentage of NiO in the composite and is 6.00 × 10 −2 min −1 for sample with the highest percentage of NiO. Rate constants for the second and third runs are estimated to be 4.4 × 10 −2 and 4.2 × 10 −2 min −1 which are promising. The main mechanism of enhancement of photocatalytic activity of the composites is identified as the more effective separation of the photogenerated free charge carries due to the internal electric field at the ZnO-NiO interface. Sharp decrease in the relative intensity of the band-band emission of ZnO at ~ 380 nm in the case of composite samples and analysis of the relative position of the conduction band and valence band edges of ZnO and NiO support the proposed mechanism.

Phytogenic Synthesis and Characterization of NiO-ZnO Nanocomposite for the Photodegradation of Brilliant Green and 4-Nitrophenol

“…Due to industrial revolution, environmental pollution exponentially increases with passage of time by releasing carcinogenic and mutagenic hazardous wastes and their side products to aqueous environment [1,2]. Major contributors of water and air contamination are food, paper, textile, and pharmaceutical industries; among these, textile industries produce many toxic substances, and due to nonbiodegradability and stability of organic pollutants, they are considered deadly [3,4]. Different dyes such as methylene blue, golden yellow, and eriochrome black T have wide range of applications, but they are lethal for all life forms [5][6][7].…”

“…Different methods are in practice for eradication of dyes such as adsorption, membrane filtration, biological treatment, electrochemical treatment, photocatalytic degradation, ozonation, oxidation, chemical precipitation, and ion exchange [11]. Photocatalysis is cost-effective, environmentfriendly method for removal of dyes where the photocatalysts such as NiO, TiO 2 , SnO 2 , ZnO, and WO 3 , are used for removing dyes [4]. Development of photocatalytic technology improves the water quality [12].…”

“…Bimetallic composite shows better magnetic, thermal, catalytic, and optical properties [15]. Nanocomposites of ZnO-NiO are used as photocatalysts and have better properties than their individual particles and their efficiency increases by increasing NiO concentration [4]. NiO/ZnO nanocomposite is used in transparent conducting thin films for OLED applications [16].…”

“…In the recent past, different methods such as combustion method, coprecipitation method, and sonochemical route had been employed to synthesize NiO-ZnO composites [4,18]. However, these methods include the used toxic precursor chemical, solvents, and reducing and stabilizing agents along with expensive instruments.…”

Role of nanohybrid NiO–Fe3O4 in enhancing the adsorptive performance of activated carbon synthesized from Yemeni-Khat leave in removal of Pb (II) and Hg (II) from aquatic systems

“…From the EDX data, the 0.2 KeV short signal is attributed to carbon [ [57] , [58] , [59] ], whereas the 0.60 KeV middle band is attributed to oxygen [ 58 ]. Iron is thought to be responsible for the bands that formed at 6.46 and 7.41 keV, while other signals that existed at 0.90, 7.50, and 8.20 keV are related to the presence of nickel [ [59] , [60] , [61] , [62] , [63] ]. These bands demonstrate that Ni–Fe oxides presented onto the surface of AC, supporting the successful formation of NF/AC nanocomposites.…”