Elsevier

Optical Materials

Volume 124, February 2022, 111961
Optical Materials

Solar-light-driven photocatalytic performance of Cr and Co doped Sr1-xCoxFe12-yCryO19 and effect of doping on optical, structural and dielectric properties

https://doi.org/10.1016/j.optmat.2021.111961Get rights and content

Highlights

  • SrFe12O19 doping was done with Co and Cr ions by facile micro-emulsion approach.

  • Doping effect was evaluated on the basis of dielectric, optical and photocatalytic properties.

  • Photocatalytic activity was evaluated by degrading RhB dye under solar light exposure.

  • The Sr1-xCoxFe12-yCryO19 revealed significantly higher PCA under solar light irradiation bersus SrFe12O19.

Abstract

A series of Co2+ and Cr3+ doped strontium hexaferrite (Sr1-xCoxFe12-yCryO19) nanoparticles were synthesized via micro-emulsion technique. Effect of Co and Cr ions doping was estimated using structural, dielectric, photocatalytic and optical properties of Sr1-xCoxFe12-yCryO19. The Sr1-xCoxFe12-yCryO19 were characterized employing X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR), (Scanning electron microscopy) SEM and UV–Vis spectroscopy. The XRD analysis confirmed formation of hexagonal M-type ferrites with average crystallite size of 38 nm. Dielectric properties analysis revealed that the of Sr1-xCoxFe12-yCryO19 has high dielectric constant, low dielectric and tangent loss versus SrFe12O19. The band gap energy decreased with the Co2+ and Cr3+ contents due to incorporation of sub band gaps and reduction of particle size. The photocatalytic activity (PCA) of Sr1-xCoxFe12-yCryO19 was evaluated by degrading the Rhodamine B (RhB) dye under solar light irradiation. The Sr1-xCoxFe12-yCryO19 degraded up to 87.6% of dye in 45 min of solar light irradiation with rate constant of 0.03834 min−1. Results revealed that Co2+ and Cr3+ doping tuned the optical properties and Sr1-xCoxFe12-yCryO19 has potential to harvest the solar light for photocatalytic applications. The high electrical conductivity and tuned band gap make such materials as feasible to utilize them efficiently in photovoltaic cells, SOFCs and as an encouraging photocatalyst for water remediation.

Introduction

The nanoscale materials preparation is one of promising field in nanotechnology because of their diverse application due to the extraordinary properties such as higher surface area, catalytic, optical, magnetic and thermal properties. Various approaches for synthesizing nanosized material have been developed and applied for the preparation of functional materials [[1], [2], [3], [4]]. The nanostructure hexagonal ferrites having general formula AM12O19 where (A = Sr, Ba, Pb; M = Fe, Al etc) is highly interesting class of material [5,6]. Ba, Sr M-type hexaferrites are the most widely used materials for permanent ferrite magnets, which are in high demand due to their low cost and chemical stability. Hard-magnetic materials like M-type strontium hexaferrites (SrFe12O19) have gained a lot of interest in microwave integration technology. Because of an excellent microwave (MW) absorption capacity, which allows them to decrease electromagnetic backscattering and interference at higher microwave ranges? Furthermore, Sr hexaferrites have emerged as permanent magnets due to their exceptional magnetic properties [[7], [8], [9], [10]]. The magnetocrystalline anisotropy, high electrical resistivity and high saturation magnetization property of nanocrystalline substituted strontium hexaferrite reported to be promising for many practical application such as fabrication of permanent magnets, magnetic recording media, various components in microwave devices, electromagnetic properties, electronic components, telecommunication, and radio-frequency devices [11,12].

The most efficient way to improve and enhance the magnetic properties of SrM ferrite (including saturation magnetization, anisotropy field, coercivity and magnetic resonance frequency [13] is by substituting various ions i.e. Sm3+, Mn3+, Ni2+, Al3+, Co2+, Cr3+, Cu2+, and Zn2+ as single and co-doped versions in the crystallographic sites [14]. Numerous routes such as conventional solid state method [15], sol gel [16], auto combustion [17], hydrothermal [18], micro-emulsion [19] and co-precipitation [20] have been adopted to synthesize doped Sr-hexaferrite. Micro-emulsion method provides best setup to formulate morphologically enriched Sr-hexaferrite nanostructure having perfect magneto-crystalline anisotropic, superior coercivity and electromagnetic properties [21].

To date, different approaches have been applied for the elimination of dyes from wastewater and all approaches are not feasible equally and also some cause secondary pollution issue, unable to remove the pollutant completely and are costly [[22], [23], [24], [25], [26]]. The RhB is widely used in dyeing, printing, and leather industries, and resultantly, discharged into the environment and cause various health impacts like skin, respiratory, eyes, and nervous system are affected in response to this dye exposure. The RhB dye is water soluble mostly used in textile industry is carcinogenic, highly stable and non-biodegradable under environmental conditions. Therefore, it is need to employ a competent approach to remediate this dye in effluent before discharging in to water [27,28]. Among the alternative chemical processes, photodegradation employing metal oxides under the solar light has proven as an effective approach that is both environmentally beneficial and low-cost. Because the solar spectrum contains a small amount of UV (4%) and a large amount of the visible light (46%), it is important to create innovative effective photocatalyst active under the solar light, that can be accomplished by altering electronic structure and regulating band-gap by substitution [29,30]. For this, an active photocatalyst is required and NPs performed efficient job in this regard [[31], [32], [33]]. On the other hand, the catalyst active under solar light irradiation are also regarded economical versus catalysts active under UV light irradiation. The modification (band gap tuning) of NPs with active moieties make material active under solar light. To improve the optical properties doping is best. Attempts have been made to enhance properties of Sr-hexaferrite, numerous cations such as In3+, Al3+, Cr3+, Ga3+ and cation combinations such as Nb4+-Zn2+, Ti4+- Co2+, Ti4+-Ni2+, La3+-Co2+, Gd3+-Co2+, Ti4+-Mn2+, Ir3+-Zn2+ and Sm+3-Co+2 have been studied as dopant to enhance the physicochemical properties [[34], [35], [36], [37]] (Table 1). Particularly, Sr-hexaferrite doped by different cation combinations reflect enhancing electrical resistivity and reducing the magnetocrystalline anisotropy, which exhibits preferable properties for diverse applications. High electrical resistivity materials are most desirable microwave devices applications [6,[38], [39], [40]].

In the present study, the Co2+ and Cr3+ doped Sr-hexaferrites (Sr1-xCoxFe12-yCryO19) were synthesized by using micro-emulsion approach and the influence of substitution in the structure of SrFe12O19 was examined on basis of structural, optical and dielectric characteristics. The PCA of Sr1-xCoxFe12-yCryO19 is evaluated for RhB dye.

Section snippets

Chemical and reagent

The Sr(NO3)2, Fe(NO3)3, and Co(NO3)2·6H2O were obtained from the Sigma Aldrich. The Cr(NO3)3.3H2O, C19H42BrN and Rhodamine B dye were obtained from the Merck, NH4OH was obtained from the AnalaR.

Synthesis of Sr1-xCoxFe12-yCryO19 NPs

The hexaferrite nanoparticles of M-type with the composition of Sr1-xCoxFe12-yCryO19 were prepared by microemulsion approach. The stoichiometric amounts of the metal salts were dissolved in distilled water and stirred for 3 h on hot plate at 50 °C. The solution of the CTAB used as surfactant and was

Structural analysis

The XRD pattern of Sr1-xCoxFe12-yCryO19 is depicted in Fig. 3. The peaks are oriented at 2θ = 23.1°, 34.2°, 35.7°, 40.3°, 49.8°, 55.1°, 57.4° which are indexed with (006), (114), (108), (205), (209), (217), (218) planes, which matched with the standard (JCPDS# 33–1340) [41]. The formation of SrFe12O19 hexagonal M-type hexaferrite is conformed from XRD analysis. As the dopant (x, y) contents increased, there is reduction in the intensity of the diffracted angle towards lower 2θ and the

Conclusion

Micro-emulsion route was employed for the fabrication of Sr1-xCoxFe12-yCryO19 NPs, which were compared for structural, dielectric, photocatalytic and optical properties versus SrFe12O19. The hexagonal M-type ferrites with average crystallite size of 38 nm was formed. It was observed that the Co2+ and Cr3+ ions significantly affected the dielectric, optical and photocatalytic properties. The Sr1-xCoxFe12-yCryO19 showed higher dielectric constant, low dielectric and tangent loss versus SrFe12O19.

CRediT authorship contribution statement

Ismat Bibi: Conceptualization, Supervision, Data curation. Shahid Iqbal: Methodology, Writing – original draft. Farzana Majid: Resources, Software, Validation. Noor Fatima: Formal analysis, Investigation. Norah Alwadai: Project administration, Funding acquisition. Munawar Iqbal: Visualization, Writing – original draft, Writing – review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

The authors express their gratitude to Princess Nourah bint Abdulrahman University. Researchers Supporting Project (Grant No. PNURSP2022R11), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.

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