Fabrication of Ce3+ substituted nickel ferrite-reduced graphene oxide heterojunction with high photocatalytic activity under visible light irradiation

https://doi.org/10.1016/j.jhazmat.2020.122593Get rights and content

Highlights

  • NiCeyFe2-yO4 /rGO nanocomposite exhibited excellent photocatalytic activity and stability.

  • The degradation of organic pollutants by catalyst was confirmed by multiple techniques.

  • The large surface area and magnetic nature of the catalyst suggested the commercial applications of prepared photocatalyst.

Abstract

In the current investigation, graphene (rGO)-supported cerium substituted nickel ferrite (NiCeyFe2-yO4 y = 0.05) photocatalyst was prepared via two-step wet chemical approach. The resulting NiCeyFe2-yO4/rGO nanocomposite exhibited excellent photocatalytic performance and stability. Moreover, the photocatalytic activity of NiCeyFe2-yO4/rGO nanocomposite was also investigated comparatively with NiCeyFe2-yO4 nanoparticles. As compared to the NiCeyFe2-yO4 nanoparticles, NiCeyFe2-yO4/rGO nanocomposite showed superior photocatalytic efficiency and recycling stability for MB degradation, which is two times that of bare NiCeyFe2-yO4 nanoparticles. After visible light irradiation for 70 min, 94.67 % of MB dye was removed by NiCeyFe2-yO4/rGO nanocomposite whereas only 50 % of MB dye was removed by NiCeyFe2-yO4 nanoparticles. The increase in photocatalytic performance is mainly ascribed to formation of NiCeyFe2-yO4/rGO heterojunction which not only assist in separation of photo-induced charge carriers, but also sustain a strong redox ability. Moreover, the photo-corrosion of NiCe0.05Fe1.95O4 nanoparticles is inhibited through transfer of photo-induced electrons of NiCe0.05Fe1.95O4 nanoparticles to rGO. A possible photo-degradation mechanism based on reactive species trapping experiments has been proposed. The effect of various factors like pH, temperature and catalyst dosage has also been explored. Facile synthesis method, excellent photocatalytic performance for organic pollutants and superior reusability suggest that NiCeyFe2-yO4/rGO photocatalyst possesses high potential for large-scale pollutant treatment.

Graphical abstract

Ce-doped spinel nickel ferrite nanoparticles decorated onto the reduced graphene oxide sheets exhibited the excellent visible light driven photocatalytic activity.

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Introduction

At the present time, water pollution has become an important environmental issue which is affecting our daily life (Omotunde et al., 2018; Liu et al., 2011). Over the past few decades, many people used traditional biological and physical techniques to remove the chemical pollutants present in wastewaters. But those techniques proved to be inefficient due to the generation of secondary pollutants and high energy consumption (Ding et al., 2017; Mia et al., 2017; Hashimoto et al., 2005). Lately, photocatalysis technology has attracted great attention of researchers towards the photocatalyzed degradation of organic pollutants. Photocatalysis technology has a huge potential in solving the water pollution problems because it is ecofriendly, consume low energy, and has high catalytic efficiency (Nakata and Fujishima, 2012).

As it is well known, whether the photocatalysis technology can be used for practical applications depends upon the degradation efficiency and reusability of the photocatalyst. Currently, spinel ferrites have got many researchers’ attention since they have excellent chemical stability. The most important thing is that they are magnetically separable and have good reusability. Some of the current reports shows the potential of spinel ferrites in visible light driven photocatalytic applications (Pullar, 2012; Fox et al., 1954; Kumar et al., 2020; Zhu et al., 2008). Among the ferrites, due to unique properties such as low price, a large abundance of nickel and environmental benignity, nickel ferrite has got special attention of researchers and it is the most important magnetic material which has high electrical resistivity, environmental stability and high curie temperature (Liu et al., 2014; Talebi, 2017; Kumar, 2013). Although the nickel ferrite has a bandgap of 2.1 eV, little reports are available on its photocatalytic applications in literature. Even though, nickel ferrite is photocatalytically inactive material under visible light illumination, it is possible to improve the efficiency of the photo-generated charge carriers’ separation in nickel ferrite by substituting rare earth metals, which results in enhanced photocatalytic activity. It has been reported that N Rezlescu et a1. (Rezlescu et al., 2020) investigated the effect on electrical and magnetic properties of nickel-zinc ferrite by rare earth substitution. Harish, K.N. et al. (Harish et al., 2013) reported the effect of Nd3+ ions substitution on the structure and photocatalytic performance of nickel ferrite nanoparticles under visible light. H. Javed, et al. (Javed et al., 2019) has reported the influence of Nd3+ ions doping on structural, magnetic and electrical properties of Ni-Zn spinel ferrite. However, owing to narrow bandgap, fast recombination of photo-induced electron-hole pairs suppresses the photocatalytic efficiency of substituted ferrites. Therefore, substituted ferrites are coupled with some suitable carriers to promote the photo-induced charge separation, resulting improved photocatalytic performance.

Due to its large surface area, good chemical and electrical properties, excellent mechanical stability and an efficient electron mobility, graphene (2D nanomaterial) has been employed as a support for nanoparticles. Liang, J. et al. (Liang et al., 2018) fabricated visible light active NiFe2O4-rGO composite photocatalyst using the ball-milling method, which showed excellent photocatalytic performance. Fu, Yongsheng et al. (Fu et al., 2012) investigated the effect graphene on the photocatalytic activity of manganese ferrite nanoparticles. He, Guangyu et al. (He et al., 2015) synthesized CoFe2O4−rGO heterojunctions for efficient removal of organic pollutants from wastewaters. Deng, Fang et al. (Deng et al., 2017) explained that the presence rGO in the rGO/SnS2/ZnFe2O4 system effectively improve its photocatalytic efficiency. A. Iftikhar et al. (2019) found that the addition of rGO in the Ni0.4Co0.6Er0.045Fe1.95O4/rGO nanocomposite system enhance its photocatalytic performance. Nazim et al. (2016) prepared the magnetically separable CoxZn1-xFe2O4-rGO photocatalyst with improved photocatalytic efficiency.

From literature survey, it is revealed that no research has been conducted on the photocatalytic application of rGO supported cerium substituted nickel ferrite nanoparticles under visible light illumination to date. In this work, we have synthesized the visible light active NiCe0.05Fe1.95O4 nanoparticles and NiCe0.05Fe1.95O4/rGO nanocomposite photocatalysts by following a two-step wet chemical approach. Photocatalytic efficiency of prepared samples has been checked using a model organic pollutant methylene blue (MB) under visible light radiations. The role of reactive species was observed by using a free radical scavenging method. A possible MB dye degradation mechanism has been proposed to illustrate the processes involved in photocatalysis. The effect of different reaction parameters, such as pH, temperature and photocatalyst dosage on photocatalytic efficiency has also been studied over NiCe0.05Fe1.95O4/rGO nanocomposite photocatalyst in a comprehensive manner. The results imply that NiCe0.05Fe1.95O4/rGO nanocomposite photocatalyst has huge potential for photocatalytic applications under visible light irradiation.

Section snippets

Chemicals

Iron Nitrate Nonahydrate (99.9 % Fe(NO3)3.9H2O), Cerium Nitrate Hexahydrate (99.9 % Ce(NO3)3.6H2O), Sodium Hydroxide (98 % NaOH,) and Nickel Nitrate Hexahydrate (99.9 % Ni(NO3)2.6H2O, Graphite Powder, Terephthalic Acid, Potassium Permanganate (99 % KMnO4), Sodium Chloride (NaCl), Pentachlorophenol, Sodium Nitrate (99 % NaNO3), Phenol, Hydrogen Peroxide (30 % H2O2) and Conc. Sulfuric Acid (98 % H2SO4) were used in this research. All the chemicals used for the synthesis of powder materials were

XRD analysis

X-ray diffraction (XRD) studies were performed to find the crystalline structure and composition of pure and cerium (Ce3+) substituted NiFe2O4 nanoparticles and NiCe0.05Fe1.95O4/rGO nanocomposite as shown in Fig. 1(a). As it is obvious from Fig. 1, all prepared samples contain similar XRD patterns. All diffraction peaks correspond to the cubic spinel structure of NiFe2O4 (ICCD # 00−010-0325) having no impurity and secondary phase, signifying the high crystallinity of all prepared samples. After

Conclusions

In summary, NiCe0.05Fe1.95O4/rGO photocatalyst successfully prepared using a two-step facile wet chemical approach, exhibited excellent photocatalytic performance and stability for photo-degradation of MB dye, which achieved within 70 min. Cerium substituted nanoparticles was also prepared for comparative study. The NiCe0.05Fe1.95O4/rGO nanocomposite (94.67 %) exhibited superior photocatalytic activity as compared to NiCe0.05Fe1.95O4 nanoparticles (50.08 %) towards MB dye degradation under

Authors statement

1. Abdur Rahman (All experimental work)

2. Muhammad Farooq Warsi (Being corresponding author, management of the entire project)

3. Imran Shakir (Contribution in analysis of photocatalysis data)

4. Muhammad Shahid (Structural analysis and contribution in analysis of electrochemical measurements data)

5. Sonia Zulfiqar (SEM, EDX, BET measurements and assisted in data interpretation).

Declaration of Competing Interest

None.

Acknowledgement

Authors are thankful to the Islamia University of Bahawalpur (Pakistan) and Higher Education Commission of Pakistan (6276/Punjab/NRPU/ R&D/HEC/2016). Authors from King Saud University (KSU) sincerely appreciate the KSU for their contribution through Researchers Supporting Project (RSP-2019/49). Dr. Sonia Zulfiqar is highly grateful to American University in Cairo (AUC) for financial support through STRC mini-grant and research project No. SSE−CHEMS.Z.-FY19-FY20-FY21-RG

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