Synthesis of novel g-C 3 N 4 /KBiFe 2 O 5 composite with enhanced photocatalytic efficiency
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Bull Mater Sci (2020) 43:257 https://doi.org/10.1007/s12034-020-02232-1
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Synthesis of novel g-C3N4/KBiFe2O5 composite with enhanced photocatalytic efficiency RANJAN RAI and MURALIKRISHNA MOLLI* Department of Physics, Sri Sathya Sai Institute of Higher Learning, Prasanthinilayam, Anantapur 515134, India *Author for correspondence ([email protected]) MS received 5 February 2020; accepted 27 March 2020 Abstract. Novel graphitic carbon nitride (g-C3N4)/potassium bismuth ferrite (KBiFe2O5) composite photocatalysts were synthesized using facile grinding and calcination method. X-ray diffraction, transmission electron microscopy, scanning electron microscopy and UV–visible diffuse reflectance spectroscopy analysis were carried out to investigate structural, morphological and optical properties of the prepared samples. The photocatalytic properties of the samples were studied by photocatalytic degradation of methylene blue under visible light irradiation. The composite showed enhanced photocatalytic efficiency compared to both pristine g-C3N4 and KBiFe2O5. Out of four composites with different weight percentages of KBiFe2O5, one with 30 wt% showed the maximum photocatalytic efficiency. Samples with a higher content of KBiFe2O5 showed decreased photocatalytic efficiency indicating 30 wt% as the optimum composition. The increase in the photocatalytic efficiency is mainly due to efficient charge separation of photo-generated electron–hole pairs in the composites. The possible mechanism for the photo-catalysis of g-C3N4/KBiFe2O5 composites was also proposed. Keywords.
1.
Photo-catalysts; composites; brownmillerite; graphitic carbon nitride; KBiFe2O5.
Introduction
Photocatalysis is one of the important advanced oxidation processes for pollutant degradation [1]. It also finds application in photocatalytic water splitting [2,3], hydrogen production, CO2 photoreduction, etc. [4,5]. TiO2, ZnO and SnO2 are a few semiconductors which are proven as efficient photocatalysts for the above applications owing to their efficient absorption capability in ultraviolet region of solar spectrum, high chemical stability, low cost and nontoxicity [6]. But due to their wide band gap they can absorb only in the ultraviolet region which forms only 5% of the solar spectrum. So, visible-light-driven photocatalysis is essential for practical applications [7]. Graphitic carbon nitride (g-C3N4) is one of the efficient metal-free photocatalysts [8]. It is highly stable even in more alkaline and acidic medium, has narrow band gap of 2.7 eV and an appealing electronic structure [9]. But pristine g-C3N4 suffers from a high recombination rate of photogenerated electron–hole pairs, low specific surface area etc., which leads to overall low photocatalytic efficiency [10]. Similarly, potassium bismuth ferrite (KBiFe2O5), a new brownmillerite compound with A2B2O5 crystal structure [11], has narrow band gap and efficient absorption in the visible region, making it suitable for photocatalytic
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