Enhanced photo catalytic properties for environmental applications of non-metal doped nickel oxide

This study investigates the process of hydrothermal synthesis to create a nano-composite (NiO-BS-GO) by incorporating Boron (B) and Sulfur (S) into Nickel Oxide (NiO) together with Graphene Oxide (GO). The resulting nanocomposite exhibits improved photocatalytic characteristics. The combination demonstrated a substantial enhancement in both optical and photocatalytic degradation of methylene blue (MB) and Rhodamine B (RhB) when exposed to visible light. This improvement is credited to the greater surface area, enhanced charge separation, and increased absorption of visible light. The nanocomposite composed of NiO-BS-GO exhibited remarkable stability and reusability, indicating its promising suitability for environmental remediation purposes.

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Introduction

Water pollution is a pressing environmental problem that requires effective photocatalysts for treating wastewater [1][2][3][4] . Nickel Oxide (NiO) exhibits potential, but its photocatalytic activity needs enhancement. The characteristics can be enhanced by doping NiO with Boron (B) and Sulfur (S) and adding Graphene Oxide (GO) [5][6] . Water is an essential and diverse feature for all living organisms, and contamination of water resources demands careful consideration [7][8] . Industrial effluent, including pesticides, herbicides, dyes, and organic pollutants, is a significant source of water pollution [9][10][11] . Even trivial amounts of these pollutants can significantly impact ecosystems and contribute to climate change [12] . The dyeing processes and various industrial activities release effluents containing colorful, nonbiodegradable, and hazardous chemicals. Such wastewater is a major contributor to methane emissions (about 10%), leading to global warming. Thus, treating wastewater before its release into rivers is imperative to minimize environmental damage. Non-biodegradable chemicals and soluble dyes are among the primary causes of water pollution [13,14] . Due to overcrowding, food consumption, and industrialization, water pollution is rising [15,16] . In developing countries, lakes and rivers are heavily contaminated, making this problem worse. Water shortages and microbiological and chemical pollution plague many rural communities. The UNO estimates that 50% of impoverished nations' populations suffer from health issues from dirty drinking water. Even though the world possesses 3% freshwater reserves, only 0.01% is appropriate for human use, and waterborne illnesses kill 5 million people annually [17][18][19] . As population grows, freshwater scarcity for sustainable living becomes a serious challenge [20] . Graphene Oxide (GO) is ideal for visible-light-responsive nanocomposites. Because GO speeds up light-induced charge carrier recombination [21][22][23][24][25][26] . Graphene Oxide (GO) accepts electrons from copper sulfide's conduction band [27][28][29] . This mechanism slows recombination by lengthening electron paths [30] . When Boron (B) is doped into the π-framework of GO, flaws increase its surface area, generating more adsorptive sites for pollutant molecules [31][32][33] . Doped graphene oxide contains nitrogen, phosphorus, iodine, and boron [34][35] .

International Journal of Advanced Chemistry Research https://www.chemistryjournals.net

Boron doping is notable because its size matches graphene oxide, allowing it to fit into the lattice structure and increase charge resistance [36][37][38] . BGO has been intensively explored for its potential in environmental and energy applications because boron adds active sites around graphene oxide's edges [39,40] . Photo catalytic pollutant breakdown using B-doped graphene oxide and semiconductor materials has received little attention [41][42][43][44] . Because graphene oxide is selectively doped with non-metal atoms. BGO-based nanocomposites' ability to degrade pollutants needs further study [45][46][47][48] .

This study shows a very efficient two-step technique for creating BGO-CuS by doping carbon-based Graphene Oxide (GO) with non-metal (B) and linking it with CuS via hydrothermal synthesis [49][50][51][52][53] . The novel nanocatalyst was tested for its photocatalytic breakdown of Methylene Blue (MB) in sunshine [54][55][56] . Boron as a dopant in graphene oxide reduced the bandgap and increased electrical conductivity. The initiative seeks to build a photocatalyst that increases photocatalytic activity under sunlight [57][58] .

Materials and Methods

Materials and Methods

Synthesis of NiO/GO composite with B and S doping

The composite was fabricated by a hydrothermal technique: Combine 1.5 grams of nickel nitrate hexahydrate (Ni(NO₃)₂•6H₂O), 0.2 grams of boric acid (H₃BO₃), and 0.3 grams of thiourea (CH₄N₂S) in 40 milliliters of deionized water. Introduce 0.5 grams of graphene oxide (GO) and subject it to ultra-sonication for a duration of 30 minutes.

Place the mixture into a Teflon-lined autoclave with a capacity of 100 mL and heat it at a temperature of 180 °C for a duration of 12 hours. Rinse the product using deionized water and ethanol, followed by drying at a temperature of 60 °C for duration of 24 hours [59][60][61][62] . The XRD patterns verified the presence of a face-centered cubic structure in NiO, along with extra peaks suggesting the successful doping of B and S, as well as the presence of GO. The Scanning Electron Microscope (SEM) images revealed that the NiO-BS-GO composite possesses a sheetlike structure, which is distinct from the spherical shape of pure NiO. The presence of Ni, B, S, O, and carbon (from GO) was confirmed using EDX analysis. The UV-vis spectroscopy analysis showed that the composite material had a reduced band gap energy, which suggests that it has an improved ability to absorb visible light.

Characterization techniques

Characterization techniques

BET analysis and optical analysis of nanocomposites

The specific surface area of nanocomposites such as NiO-BS-GO can be determined using nitrogen gas adsorption data and the Brunauer-Emmett-Teller (BET) method. In a study, the BET surface areas of these nanocomposites were found to be 25.24 m²/g. This high surface area indicates that doping results in a significant increase in surface area.

The relationship between doping and structural integrit

The structural stability of NiO can be enhanced by doping it with Boron (B) and Sulfur (S). The substitution of nickel and oxygen atoms in the NiO lattice with boron and sulfur atoms results in the formation of a stronger structure that exhibits enhanced resistance to deterioration over time. The use of Graphene Oxide (GO) creates a robust and pliable framework that sustains the NiO particles. Graphene oxide (GO) sheets function as a framework, preventing the clustering of NiO particles and preserving a large surface area, which is essential for efficient photocatalytic performance.

Enhanced electrical charge division and decreased combination of charges

The process of charge separation is enhanced by the combination of B and S doping and the integration of GO, resulting in improved charge separation. The recombination of electrons and holes in photo catalysis is mitigated due to the presence of dopants, which induce localized states that effectively capture and immobilize the charge carriers. Enhanced Electron Transfer: The inclusion of GO improves the channel for electron transfer, hence diminishing the likelihood of electron-hole recombination. As a result, this enhances the efficiency of photo catalytic activities and extends the effective lifespan of the material.

Increased surface area and catalytic sites

The Nano composite structure, consisting of Graphene Oxide (GO) sheets dispersed with Nickel Oxide (NiO) particles, offers an expanded surface area. This guarantees the presence of a greater number of active sites for photo catalytic processes, hence improving both the overall activity and stability. Catalytic sites are formed by the introduction of dopants and Graphene Oxide (GO). These sites exhibit enhanced reactivity and stability by effectively inhibiting the sintering or agglomeration of NiO particles, hence preserving the active surface area.

Photocorrosion resistance Photocorrosion resistance:

The addition of Boron (B) and Sulfur (S) to NiO improves its ability to resist photocorrosion. Photocorrosion is a prevalent problem in photo catalysts, characterized by the deterioration of the material due to extended exposure to light. Dopants serve to enhance the stability of the NiO lattice, hence reducing its vulnerability to photo corrosion. GO Protection: Graphene Oxide (GO) functions as a protective barrier that absorbs a portion of the photogenerated holes, thereby diminishing the oxidative stress on nickel oxide (NiO) particles. This defensive mechanism additionally improves the resilience of the composite.

Discussion

Due to its photocatalytic and stability, the NiO-BS-GO nanocomposite is a diverse and powerful environmental solution. Multiple applications of this sophisticated material have shown remarkable efficiency, contributing to environmental sustainability.

It can be used in following applications 1. Aquatic filtration and effluent processing:

The nanocomposite effectively remediates industrial and municipal wastewater by degrading organic pollutants including colors and medications. Its visible light photocatalytic activity breaks down persistent organic pollutants (POPs), minimizing their environmental impact.

Air purification:

Air purification:

Acknowledgement

AcknowledgementWe would like to acknowledge the PG department of chemistry Ranchi University Ranchi Jharkhand for kind support and providing technical support.

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FESEM image of nickel oxide doped with boron and sulphur and GO

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Photocatalytic activity of NiO-BS-GO nanocomposite

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