Metal Oxide Heterojunction for Photocatalytic Activities

Summary

The development of a heterojunction boosts the photocatalytic activities of solution combustion synthesis, which is a time-/energy-efficient process. Advanced analytical characterization techniques were used in this protocol to evaluate the materials' characteristics, and nanocomposites demonstrated improved acid orange-8 dye degradation.

Abstract

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale applications. Sol-gel-based solution combustion synthesis (SG-SCS) is a simple method to produce ordered porous materials. In this regard, Pearson's hard and soft acids and bases theory assists in selecting host-dopant reactivity to form a proper heterojunction.

The formation of a heterojunction also changes the essential properties of the materials, improving photocatalysis via charge transfer or synergistic activities. A calcination temperature of 500 °C is ideal for this process based on the results of the stability assessment via a differential thermogravimetry ratio analysis (DTG).

The nanoscale dimensions of the nanoparticles (NPs) and nanocomposites (NCs) generated were validated using X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Furthermore, the scanning electron microscopy micrographs and BET analyses confirmed the porosity nature of the materials. HRTEM, X-ray photoelectron spectroscopy, and energy-dispersive X-ray investigations established the materials composition. The study found that NCs degraded the acid orange 8 (AO8) color more efficiently than bare ZnO.

Introduction

Environmental protection has become a major concern with the rapid rise in companies worldwide. Consequently, nanotechnology-based nanomaterials (NMs) and their synthesis have attracted researchers' attention over bulk materials in the modern scientific world¹. Several physicochemical approaches have been adapted to treat organic and inorganic contaminants^2,3. In this regard, due to its simplicity and capability of dissolving toxins without creating secondary contamination, heterogeneous photocatalysis is regarded as an adaptive remediation technique⁴. Studie....

Protocol

1. Nanomaterial synthesis

1. ZnO-Mn₂O₃ nanocomposite synthesis
   1. Synthesize nanocomposites using poly-vinyl alcohol as surfactant and a complexing agent-assisted SG-SCS approach. For a graphical illustration of the SG-SCS approach, see Supplementary Figure S1.
   2. Dissolve 1.5 g of PVA polymer in 100 mL of distilled water with continuous stirring on a magnetic stirrer for about 15 min at 115 °C²³.
   3. Pou.......

Discussion

The present protocol describes the synthesis of nanocrystals using a bottom-up strategy with precise shape, size, and structure. The study observed that the nucleation and growth of nanocrystals were significant before forming the nanocrystals. Here, the ZnO and manganese oxides were synthesized based on LaMer's group theory²⁵, which postulates the process of nanocrystal formation after reducing precursors into atoms and nuclei, leading to seed formation to produce nanocrystals. In this regard.......

Materials

Name	Company	Catalog Number	Comments
Acid orange 8	Sigma-Aldrich		65%,
Chlorine	Sigma-Aldrich	7782-50-5
Dithienogermole	Sigma-Aldrich	773881-43-9
HCl	Sigma-Aldrich	7647-01-0
Manganese nitrate (10%) salt	Sigma-Aldrich	15710-66-4	10%
Manganese sulfate monohydrate	Sigma-Aldrich		Density: 2.95 g/cm³; solubility in water: 70 g/100 mL (70 °C); 99.95%,  MnSO4.H2O
Poly (vinyl alcohol)	Sigma-Aldrich	9002-89-5	Density: 1.19–1.31 g/cm³ @20 °C, soluble in water only @ > 80 °C
Zinc nitrate hexahydrate (90%)	Sigma-Aldrich	10196-18-6	98%; Density: 2.065 g/cm³ @20 °C; solubility in water: 184.3 g/100 mL @20 °C
Instruments used
Materials name	Model	Analysis
BET (N2 adsorption-desorption isotherms)	Quanta chrome instrument.	Textural properties
DT/DTA	Shimadzu DTG-60H	Measure thermal stability
FTIR	Perkin Elmer FT-IR, Spectrum 65	Chemical bonding information
HRTEM	JEOL TEM 2100 HRTEM	Morphological, size, and composition analysis
SEM-EDX	SEM-EDX-EVO 18 with low vacuum facility and ALTO 1000 cryo attachment	Morphological analysis
XPS	AXIS ULTRA from AXIS 165
XRD	Shimadzu, XRD-7000	Crystallinity, structure, and approximate average crystallite size
Common software used
Name	Company	Use
Mendeley	Mendeley-Desktop-1.19.8-win32	For citing references
Origin	OriginPro 8	XRD, BET, UV-vis-DRS data analysis