Abstract
Towards nonconventional wastewater treatment methods for the degradation of organic pollutants in wastewater, a perovskite-based photoelectrochemical system was developed. Bismuth ferrite doped with lanthanum (La-BiFeO3, La-BFO) perovskite was synthesised through a hydrothermal method with low calcination temperature for the photoelectrochemical degradation of orange II dye and other cocktails of dyes. Photoanodes were prepared by the deposition of the perovskites on a fluorine-doped tin oxide (FTO) substrate. The photoanodes were characterised using XRD, FESEM, FTIR and UV-vis diffuse reflectance. The photoelectrochemical properties of the synthesised photoanodes were investigated with chronoamperometry and electrochemical impedance spectroscopy (including Mott–Schottky analysis). The results show that all La3+-doped BFO photoanodes exhibited a higher absorption edge in the visible light region than the undoped BFO. The photocurrent response of 10% La-BFO (the best performing electrode) exhibited a three times higher current response than the pure BFO. In addition, the electrode exhibited a good degradation efficiency of 84.2% within 120 min with applied bias potential of 2 V at a pH of 7. EIS studies showed a significant enhancement of the interfacial electron transfer of the charge carriers. The enhancements in electrode performances were attributed to the synergistic effect of the applied bias potential and the introduction of La3+ into the BFO matrix. This study therefore shows that the photoelectrocatalytic performance of BFO for water treatment can be improved by the introduction of perovskites-doping ions such as La3+.
Highlights
Water pollution is a global issue, partly because of the discharge of effluents into the environment from industries such as pharmaceutical, textiles and metallurgical
The enlarged view of diffraction peaks (104) and (110) shows a split as the lanthanum doping increases, and these splits broadened slightly to a higher angle, implying that substituting La3+ into Bi3+ brings about distortions in the lattice structure (Figure 1a insert). These results suggest the effect of doping lanthanum into the bismuth ferrite lattice, and they agree with the findings of the Singh and Weng groups [20,24]
The field emission scanning electron microscope (FESEM) image of BFO shows an irregular mixture of rods and globules, with some falling into the nanoscale
Summary
Water pollution is a global issue, partly because of the discharge of effluents into the environment from industries such as pharmaceutical, textiles and metallurgical. In PEC, as photons illuminate the catalyst, electrons are migrated to the cathode via the applied bias potential for efficient separation of photogenerated charges to combat electron–hole recombination Semiconductors, such as ZnO, TiO2, and WO3, have been utilised as photocatalyts in PEC degradation. With regards to its application in water treatment, Gao et al [15] synthesised BFO for the degradation of methyl red via the sol-gel method involving different calcination temperatures. Meng et al [24] synthesised La-doped BFO for the photocatalysis degradation of organic pollutants in water They reported that La-doped BFO photocatalysts manifested greater photocatalytic enhancement, which they attributed to reductions in electron–hole recombination, narrow band gap, low charge transfer resistance, and the smaller radius of La3+ (RLa3+ = 0.116 nm) than Bi3+ (RBi3+ = 0.117 nm). For the photoelectrocatalytic degradation experiments, Orange II, Congo red and methylene blue were selected as model organic dyes, and acetaminophen and sulfamethoxazole were selected as model pharmaceutical pollutants (See chemical structures of all the selected organic pollutants in Supplementary Figure S1)
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