Rationally designed la and Se co-doped bismuth ferrites with controlled bandgap for visible light photocatalysis

Article abstract of DOI:10.1039/c9ra03064f

Development of efficient visible light photocatalysts for water purification and hydrogen production by water splitting has been quite challenging. The activities of visible light photocatalysts are generally controlled by the extent of absorption of incident light, band gap, exposure of catalyst surface to incident light and adsorbing species. Here, we have synthesized nanostructured, La and Se co-doped bismuth ferrite (BLFSO) nanosheets using double solvent sol-gel and co-precipitation methods. Structural analysis revealed that the La and Se co-doped BFO i.e. Bi_0.92La_0.08Fe_1-xSe_xO₃ (BLFSO) transformed from perovskite rhombohedral to orthorhombic phase. As a result of co-doping and phase transition, a significant decrease in the band gap from 2.04 eV to 1.76 eV was observed for BLFSO-50% (having Se doping of 50%) which requires less energy during transfer of electrons from the valence to the conduction band and ultimately enhances the photocatalytic activity. Moreover, upon increase in Se doping, the BLFSO morphology gradually changed from particles to nanosheets. Among various products, BLFSO-50% exhibited the highest photocatalytic activities under visible light owing to homogenous phase distribution, regular sheet type morphology and larger contact with dye containing solutions. In summary, La, Se co-doping is an effective approach to tune the electronic structure of photocatalysts for visible light photocatalysis.

Full text of DOI:10.1039/c9ra03064f

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Rationally designed La and Se co-doped bismuth
ferrites with controlled bandgap for visible light
photocatalysis
Cite this: RSC Adv., 2019, 9, 17148
b
c
a
d
M. Umar,a Nasir Mahmood,
Saif Ullah Awan, Sabeen Fatima, Asif Mahmood
*
a
*
and Syed Rizwan
Development of efficient visible light photocatalysts for water purification and hydrogen production by
water splitting has been quite challenging. The activities of visible light photocatalysts are generally
controlled by the extent of absorption of incident light, band gap, exposure of catalyst surface to
incident light and adsorbing species. Here, we have synthesized nanostructured, La and Se co-doped
bismuth ferrite (BLFSO) nanosheets using double solvent sol–gel and co-precipitation methods.
Structural analysis revealed that the La and Se co-doped BFO i.e. Bi0.92La0.08Fe1ꢀxSexO3 (BLFSO)
transformed from perovskite rhombohedral to orthorhombic phase. As a result of co-doping and phase
transition, a significant decrease in the band gap from 2.04 eV to 1.76 eV was observed for BLFSO-50%
(having Se doping of 50%) which requires less energy during transfer of electrons from the valence to
the conduction band and ultimately enhances the photocatalytic activity. Moreover, upon increase in Se
doping, the BLFSO morphology gradually changed from particles to nanosheets. Among various
products, BLFSO-50% exhibited the highest photocatalytic activities under visible light owing to
homogenous phase distribution, regular sheet type morphology and larger contact with dye containing
solutions. In summary, La, Se co-doping is an effective approach to tune the electronic structure of
photocatalysts for visible light photocatalysis.
Received 24th April 2019
Accepted 8th May 2019
DOI: 10.1039/c9ra03064f
rsc.li/rsc-advances
solar electromagnetic radiation.11 To efficiently make use of
solar energy that contains mostly visible light, it is critical to
discover visible-light-driven photocatalysts.9 However, it is quite
challenging to design visible light driven photocatalysts
because of the large bandgap which limits excitation in the
visible region and hence limits the catalytic performance of the
designed nanomaterials. Several efforts have been made to
design effective visible light driven photocatalysts, however,
realization of photocatalysis in visible region is still far from
reality.
In recent years, the bismuth ferrite BiFeO3 (BFO) has
attracted great interest due to its multiferroics properties as this
system shows the ferroelectricity and anti-ferromagnetism.10
Besides its multiferroics property, current studies also revealed
promising visible-light driven photocatalytic properties for
BFO.12,13 The BFO as photocatalyst has attained a great attention
due to its small band gap (2.2 to 2.7 eV), chemical stability, low
cost and good response to visible-light irradiation.14 Further-
more, magnetic properties of BiFeO3 can assist in reprocessing
the photocatalyst aer the reaction via external magnetic eld.14
This avoids the damage of the catalyst over the rotations and
makes the catalyst cost-effective. There by, BiFeO3 can act as
a noble candidate for visible-light photocatalytic degradation of
organic pollutants/dyes.15 Still, as talented as BFO material is,
a few shortcomings need to overcome prior to tangible
1. Introduction
Nanoscale semiconductor-based photocatalysts have elicited
signicant consideration over the last decades due to their
possible applications in solar energy transformation and envi-
ronmental purication.1 Amongst them, titanium dioxide
(TiO2) has been demonstrated to be a dominant photocatalyst
for the degradation of abundant organic amalgams2 despite the
fact that it can only react to UV light due to its wide bandgap
(ꢁ3.2 eV). It is well known that the morphology, band-
structures, and nanocomposites with various rare-earth
metals could be the reasons for the improving photocatalytic
activity of TiO2.3–8
As solar energy comprises 47% visible and only 2% UV
radiation, these photocatalysts have inadequate activity under
aPhysics Characterization and Simulations Lab (PCSL), School of Natural Sciences
(SNS), National University of Science and Technology (NUST), Islamabad 44000,
Pakistan. E-mail: syedrizwanh83@gmail.com; Tel: +92 51 9085 5599
bSchool of Electrical and Computer Engineering, RMIT University, 124 La Trobe Street,
3001 Melbourne, Victoria, Australia
cDepartment of Electrical Engineering, NUST College of Electrical and Mechanical
Engineering, National University of Sciences and Technology (NUST), Islamabad
44000, Pakistan
dSchool of Chemical and Biomolecular Engineering, The University of Sydney, 2006,
Sydney, Australia. E-mail: asif.mahmood@sydney.edu.au; Tel: +61 3 9925 5439
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commercial and industrial applications. One serious difficulty Diffractometer (XRD) in the range of 2q ¼ 20–80ꢂ using Cu-Ka
is the high leakage current in BFO materials, essentially initi- (l ¼ 0.15418 nm) radiation with a scanning speed of 2 degree
ating from numerous impurity phases e.g. Bi2Fe4O9, Bi25FeO40 per minute. Field emission electron microscopy (FESEM,
and Bi36Fe24O57 as well as oxygen vacancies, resulting in poor Hitachi-S5500) was used for study of the microstructures and
photocatalytic behavior.16 In addition, relatively larger bandgap morphological analysis. The photon source was an Al Ka (1486.6
(2.2–2.7) further limits the excitation upon light irradiation. eV) source operating at 350 W. He–Cd laser of wavelength
Owing to these shortcomings, the BFO based materials have 325 nm was used as the excitation source during room
exhibited very poor photocatalytic degradation efficiencies14,17–21 temperature photoluminescence (PL) measurement. The PL
and the work is still going on in this eld for improving the spectrum was observed using a Hitachi luminescence spec-
catalytic activity of multi ferric systems under visible light. trometer (F-4500). Room temperature UV-Vis absorption spec-
Hence, it is pertinent to nd ways to tailor the chemistry of BFO troscopy measurements were carried out using PerkinElmer,
materials so as to obtain pure phase product with lower Lambda 950 photo spectrometer system.
bandgap in order to harness maximum activities under visible
light irradiation.22–26
Here, we present a straightforward methodology for tailoring
the inherent structure of BFO in such a way that a single phase
3. Results analysis and discussion
product could be obtained with much lower bandgap of The XRD analysis was used to investigate the crystalline structure of
ꢁ1.76 eV having sheet type morphology for enhanced contact BFO and derived nanomaterials and the results are presented in
with incident light and adsorbing species. The product was Fig. 1. The XRD patterns of pure BFO (JCPDS card no. 20-0169 and
synthesized by simple wet-chemical and double solvent sol–gel no. 42-0201) corresponds to rhombohedral structure with distorted
method. Keeping in mind the high probability of recombina- perovskite structure corresponding to R3c space group.27–29 The
tion between photo-generated electrons and holes in single dopants were systematically introduced into the BFO crystal lattice.
phase products, we introduced secondary dopants in the form The La was rstly introduced into the crystal lattice and with about
of lanthanum (La) and selenium (Se) to control the recombi- 8% addition of La, a phase pure BLFO having a composition
nation and enhance the number of delocalized electrons. A of Bi0.92La0.08FeO3 was obtained as revealed by XRD analysis (Fig. 1).
series of experiments were carried out in order to understand Aer xing the La doping concentration to 8%, the secondary
the effect of dopant upon morphology, and bandgap and the dopant was introduced into the La doped BFO. Remarkably, (012)
resulting photocatalytic activity for co-doped (La, Se) BFO peak of pure BFO sample disappeared on increase in the Se
nanosheets. Structural changes, morphologies, electronic concentration from x ¼ 0% to x ¼ 100% and structural
properties and optical measurement were performed to analyze phase transformation from rhombohedral to orthorhombic crystal
the recombination rate of charge carriers and elemental structure was observed. In addition, a slight shi in the peak
composition of the co-doped series. To the best of our knowl- positions corresponding to the (104) and (110) towards
edge, this is the rst study which reports the control of inherent higher angles were observed with Se co-doping in BLFO nano-
BFO structure via La and Se.
particles which could be ascribed to difference in ionic radius of
3+
˚
˚
˚
dopants (Se ¼ 0.64 A, La ¼ 1.032 A) than parent ions (Bi ¼ 1.03 A),
Fe (Fe3+ ¼ 0.78 A).
The XRD analysis revealed that the Se co-
30–34
˚
2. Experimental details
doping plays a critical role in phase transformation of pure BFO
A series of nanoparticles of (La, Se) co-doped BFO with empir- from rhombohedral to orthorhombic phase. The compositions with
ical formula Bi0.92La0.08Fe1ꢀxSexO3, x ¼ 0, 10%, 25%, 50%, relatively lower doping contents (x ¼ 0%, 10% and 25%) exhibited
100% labelled as BFO, BLFO, BLFSO-10%, BLFSO-25%, BLFSO- mixed phases i.e. rhombohedral and orthorhombic. In contrast,
50%, BLFSO-100% were synthesized by double solvent sol–gel compositions with relatively higher doping (x ¼ 50% and 100%)
method. These samples are abbreviated as “BLFSO” with exhibited pure orthorhombic phase.
varying concentration of Se from 10% to 100%, at xed 8% La
To further look into the impact of co-dopant on the
concentration. All chemicals were purchased from Sigma morphology of BFO, scanning electron microscope (SEM)
Aldrich commercial grade and used without further modica- measurement were carried out and presented in Fig. 2(a–e). An
tion. The precursors of Bi(NO3)3$5H2O (99.90%, pure) and overall particle type morphology was observed for BLFO as
La(NO3)3$6H2O (99.90%, pure) were stoichiometrically grinded depicted in Fig. 2(a). The doping of Se lead to signicant change
and both were dissolved in ethylene glycol (C2H6O2) and acetic in particle type morphology of BLFO and resulting Se-doped
acid (C2H4O2) with continuing stirring for 2 h at room products exhibit an overall sheet-type morphology. Relatively
temperature. On the other hand, Fe(NO3)3$9H2O (99.50%, pure) thin sheets were observed with lower doping of Se (10%) as
and Se powder (99.50% pure) were dissolved in acetic acid and presented in Fig. 2(b). Subsequent increase in Se concentration
stirred for 2 h. Both the prepared solutions were again mixed lead to relatively larger sheets possibly due to long range 2-
and stirred for 3 h on magnetic stirring. Aer that, the solution dimensional order in the structure as shown in Fig. 2(c). The
was dried in an oven at 90 ꢂC for 12 h to get a gel and then product obtained with Se doping of ꢁ50% (Fig. 2(d)) exhibited
calcined in furnace at 600 ꢂC for 3 h. For pure BFO, similar large and compact sheets which ensure exposure of large
preparation methods have been demonstrated earlier.26 Struc- surfaces for enhanced catalytic response. Going beyond ꢁ50%
tural analysis of the all samples were performed by X-ray Se doping caused distortions in the sheets leading to irregular
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Fig. 1 The XRD pattern of BLFSO with varying concentration of Se (a) 20–40 and (b) 42–80 degrees.
structure and hence compromised the overall surface of the photo-catalyst.47 It should be noted that no wavelength shi
product as shown in Fig. 2(e). was observed upon doping of Se in the BFO, rather a strong
Room-temperature photoluminescence (PL) emissions at the variation in PL intensity was observed which clearly indicates
excitation wavelength of 300 nm were measured to investigate the recombination behavior in the developed products. For
the effect of co-dopants for generation of possible defects within instance, highest intensity of the major signal at 378 nm was
the narrow bandgap of pure BFO system. Modication of band observed for BFO which was greatly reduced for co-doped
structure in a photocatalyst is fundamentally related to inter- nanostructures particularly for BLFSO-50%. Lower PL inten-
ruption or reduction in the recombination opportunities sity for BLFSO-50% nanosheets suggested reduction of radi-
through the photocatalytic progression.34–40 Fig. 3 shows the PL ative emission due to the improved recombination resistance
spectra of pure and co-doped BFO samples. The PL spectra of owing to the de-localization of excited electrons in the
each sample has asymmetric broad curve with clear peaks conduction band. This indicates the possibility of enhanced
identications at 357 nm, 378 nm, and 400 nm. The charac- photocatalytic response, higher stability and durability for
teristic PL signal at 357 nm is ascribed to the radiative emission the BLFSO-50% nanosheets. In comparison to BLFSO-50%,
of nanostructures during the recombination of electron–hole the PL analysis for BLFO-100% exhibited higher radiative
pairs, while the other signals at 378 nm, 400 nm are due to the emissions clearly indicating higher recombination rate for
emission as a result of the recombination owing to the defects, higher doping of Se leading to poor catalytic response. It can
and donor–acceptor interactions.41–44 A small kink correspond- be assumed that the Se doping of 50% would provide optimal
ing 455 nm was observed in pure BFO which correspond to ratio between La3+ and Se4+ dopants to tailor the intrinsic
bandgap of 2.72 eV. In comparison to BFO, the BLFSO-50% structure, hence leading to enhanced recombination
exhibited a much shorter bandgap of 2.43 eV at emission resistance.
wavelength of 510 nm. Interestingly, no impurity was observed
X-ray photoelectron spectrum has been performed for evalu-
close to 520 nm in BFO system as reported previously. However, ating the surface chemical states of the BLFSO sample. The peaks
we noticed an impurity peak only existing in pure BFO nano- corresponding to Bi4f, Bi4d, C1s, O1s, La3d and Se 3d can be
particles at 623 nm. Additionally, broad spectra in the range of shown in Fig. 4. Selenium has two main peaks at 55.4 eV and
640–700 nm (inset Fig. 3) was observed for BLFSO-50% and 59.1 eV corresponding to the oxidation of BFO surface with
BLFSO-100% sample. No such peak at higher wavelength was selenium. Similarly, lanthanum has 834 eV, 838.2 eV, 851.3 eV
observed for BFO. It can be speculated that the intense spec- and 854.9 eV corresponding to La3d3/2 and La3d5/2. Further C1s
trum arise due to the phase transition from rhombohedral to and O1s peaks are present at 298.8 eV and 545.3 eV. One domi-
orthorhombic occurred upon increasing Se concentration in the nant peak corresponding to Bi4f and two peaks corresponding to
derived products.
Bi4d are clearly visible at binding energy of 168.8 eV, 441 eV and
Photocatalytic activity is strongly affected by competition 466 eV. The presence of selenium and lanthanum peaks with
between the charge separation and recombination processes a positive shi in the oxygen peak exhibits the bonding of La and
and the PL emission spectra have been widely used to esti- Se over the BFO surface which in turns helps in enhancing the
mate the rate of charge recombination.45,46 According to the charge transfer over the BLFSO surface.48,49 The enhancement in
previous studies, the lower the PL emission intensity, the charge transfer further reduces the recombination rate in the
lower is the recombination rate of the photo-generated photocatalytic materials which further helps the photo catalyst in
electron–hole pairs and the greater is the photo-activity of enhancing the dye degradation.50
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Fig. 2 SEM images of (a) BLFO, (b) BLFSO-10% (c) BLFSO-25% (d) BLFSO-50% (e) BLFSO-100%.
To investigate the inuence of La3+ and Se4+ co-doping on the under UV-vis-NIR light treatment. Furthermore, the band-gaps
optical absorption of BFO, the UV-Vis diffused reectance spectra were deliberated using the Kubelka–Munk function52 (ahn)2
(DRS) of the pure BFO and BLFSO samples were measured at versus photon energy (hn) for the direct band-gap semiconductor;
room temperature, as shown in Fig. 5. The absorption band edge the extrapolation of the tail at y-axis equals to zero gives the band
of the pure BFO nanoparticles appears at 610 nm which is gap, as shown in the inset of Fig. 5 The band-gaps are 2.03, 1.99,
comparable to previous reports51 and designates that BFO can 1.96, 1.80, 1.77, 2.05 eV for the pure BFO, BLFO, BLFSO-10,
react to visible light. In association with pure BFO, the La3+ and BLFSO-25, BLFSO-50 and BLFSO-100 samples, respectively. The
Se4+ co-doped BFO samples displayed an enhanced absorption band-gap of the BLFSO-50 sample is smallest in comparison to
energy under visible light, and the absorption edge spectra that of BFO and other samples. The reduction in bandgap for
change abruptly to the near infra-red region, which is a pure red BLFSO-50 can be ascribed to relatively larger crystals, optimally
shi change in these samples. Thus, the light absorption range is tailored lattice parameters and defects which all contribute to
prolonged, which enhances the photocatalytic activity of BLFSO lowering of the band gap upon introduction of co-dopants.
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nanobers51 and Se doped BFO.26 The dye removal time taken by
the BLFSO-50% is very less ass compared to other multi ferric
nanoparticle systems (180 min, 270 min, 1 h and).40,52–54 In
comparison, compositions with other Se doping levels exhibited
much poor dye degradation activities. Higher dye degradation
activities for BLFSO-50% can be attributed to complete phase
transition from rhombohedral to orthorhombic which provide
favorable bandgap (ꢁ1.77 eV) and binding energies for
enhanced catalysis of dye species. Moreover, homogenous and
compact sheet type morphology provide higher active surface
area and larger contact with dye solution which eventually
enhance the number of exposed sites for catalytic reaction. The
activities of compositions with lower Se doping i.e. BLFSO-10%
and BLFSO-25% were limited by incomplete phase transition
which limits the photocatalytic activity. Similarly, the BLFSO-
100% exhibited much lower photocatalytic activities (58%)
which might be attributed to disruption of sheet type
morphology which limits the contact with dye containing
solution. Moreover, the stability of a photocatalyst is an
important factor for its practical applicability. So, the BLFSO-
50% photocatalyst were analyzed for four cyclic runs and as
expected it showed approximately the same activity aer
repeating the photocatalytic process under visible light which
conrmed its stability as shown in the Fig. 7.
The mechanism of photocatalytic reaction was investi-
gated to obtain more insights into higher activities obtained
from BLFSO samples. Generally, the photocatalysis usually
involves three steps: (i) absorption of photons (ii) the
production, separation of photo generated eꢀ–h+ pair (iii)
redox reactions. In this process, $OH radicals act as active
specie for degradation of organic compounds such as the
CR.55–61 These radicals are produced by capturing of their eꢀ–
h+ pair by molecular oxygen and water as described in the
following equations:
Fig. 3 Room temperature PL spectra of nanostructured (a) BFO (b)
BLFSO-50% (c) BLFSO-100%.
The photocatalytic activity of the developed samples was
investigated under visible light irradiation using xenon lamp
having 300 W power source with 800 nm lters. The Congo Red
(CR) was used was used as a model dye in aqueous solution.
Fig. 6 represents the photocatalytic activity for various samples
as a function of time. The dye solution exhibited limited dye
degradation under visible light when no catalyst was used.
However, upon addition of designed catalyst, much faster dye
degradation was observed probably due to enhanced catalytic
reaction on the surface of the catalyst. Highest levels of dye
degradation were observed for BLFSO-50% with over 90% dye
degradation in rst 30 minutes. The degradation level of the
BLFSO nanoparticles is higher than the La doped BFO
Fig. 4 XPS spectra of BLFSO sample.
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Fig. 7 The stability of BLFSO-50% photocatalyst after four cyclic runs
under visible light.
Fig. 5 Optical absorption spectra of BLFSO samples.
4. Conclusion
In summary, we report the tailoring of BFO structure with
rational addition of dopants to control the inherent crystal
structure and obtain much lower bandgap for enhanced visible
light photocatalytic response. A series of samples with xed La
concentration and varying concentration of Se (10%, 25%, 50%,
100%) were synthesized via simple double solvent sol–gel
method and co-precipitation methods. The experimentation
revealed that the bandgap of the co-doped samples could be
easily tailored by varying the dopant contents and an overall
sheet type product could be obtained. The lower bandgap
provided easy electron availability upon exposure to incident
radiation while the sheet type morphology ensured larger
contact between surface of the catalyst and the adsorbing
species, thus resulting in enhanced synergistic response and
Fig. 6 The photo-degradation efficiencies of CR as a function of higher catalytic activities. Owing to these attributes, the devel-
irradiation time under visible-light for BLFSO series of samples with
varying the Se concentration from 10–100%.
oped product exhibited excellent photocatalytic activities for
model dye, catalyzing more than 90% dye in rst 30 minutes of
exposure to visible light. We strongly believe that the method-
ꢀ
+
)
ology provide pathway for tailoring inherent structure of ferrite-
based catalysts to be used for visible light photocatalysis.
Sample + hn / sample* (eCB + hVB
(I)
(II)
+
hVB + CR / direct oxidated dye
+
+
Author's contribution
hVB + H2O / $OH + H
(III)
(IV)
(V)
ꢀ
M. Umar fabricated and characterized the samples, Saif Ullah
Awan contributed in extensive manuscript writing and analysis
of results, Nasir Mahmood, helped in characterization, Sabeen
Fatima provided help with the XPS measurement and analysis
of the sample. Asif Mahmood and Syed Rizwan conceived the
research idea and co-supervised/supervised the entire project.
+
hVB + OH / $OH
ꢀ
eCB + O2 / $O2
ꢀ
$OH + CR / CO2 + H2O (by-products)
(VI)
(VII)
ꢀ
$O2 + CR / CO2 + H2O (by-products)
These radicals react with organic pollutant (CR in our case)
and degrades it into harmless by-products (eqn (VI) and
(VII)).56,62
Conflicts of interest
There are no conicts to declare.
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12 B. Kundys, M. Viret, D. Colson and D. O. Kundys, Light-
induced size changes in BiFeO3 crystals, Nat. Mater., 2010,
9, 803–805.
Acknowledgements
The authors are thankful to Higher Education Commission
(HEC) of Pakistan for providing research funding under the
Project No: 6040/Federal/NRPU/R&D/HEC/2016 and HEC/
USAID for nancial support under the Project No: HEC/R&D/
PAK-US/2017/783. The author also thanks School of Natural
Sciences (SNS) at National University of Science & Technology
(NUST), Islamabad, Pakistan, RMIT University, Australia and
University of Sydney for technical and nancial support.
13 (a) F. Gao, X. Chen, K. Yin, S. Dong, Z. F. Ren, F. Yuan, T. Yu,
Z. G. Zou and J. M. Liu, Visible-light photocatalytic
properties of weak magnetic BiFeO3 nanoparticles, Adv.
Mater., 2007, 19, 2889–2892; (b) R. Guo, L. Fang, W. Dong,
F. Zheng and M. Shen, Magnetically Separable BiFeO3
nanoparticles with a g-Fe2O3 parasitic phase: controlled
fabrication and enhanced visible-light photocatalytic
activity, J. Mater. Chem., 2011, 21, 18645–18652; (c)
C. Reitz, C. Suchomski, C. Weidmann and T. Brezesinski,
Block copolymer-templated BiFeO3 nanoarchitectures
composed of phase-pure crystallites intermingled with
References
1 Y. Ma, X. Wang, Y. Jia, X. Chen, H. Han and C. Li, Titanium
dioxide-based nanomaterials for photocatalytic fuel
generations, Chem. Rev., 2014, 114, 9987–10043.
a
continuous mesoporosity: effective visible-light
photocatalysts, Nano Res., 2011, 4, 414–424.
¨
2 D. Kanakaraju, B. D. Glass and M. Oelgemoller, Titanium 14 (a) J. An, L. Zhu, N. Wang, Z. Song, Z. Yang, D. Du and
dioxide photocatalysis for pharmaceutical wastewater
treatment, Environ. Chem. Lett., 2014, 12, 27–47.
3 S. C. Yang, G. Chang, G. J. Yang, Y. J. Wang and B. Fang,
Photocatalytic hydrogen generation from water reduction
using orchestrated photosensitizers, Catal. Sci. Technol.,
2015, 5, 228–233.
4 D. Xu, Q. Q. Chu, Z. Wu, Q. Chen and B. Fang, J. Catal., 2015,
325, 118–127.
5 Y.-J. Wang, G. Chang, Q. Chen, G.-J. Yang, S.-Q. Fan and
B. Fang, Orchestrated photocatalytic hydrogen generation
using surface-adsorbing iridium photosensitizers, Chem.
Commun., 2015, 51, 685–688.
H.
Tang,
Photo-Fenton
like
degradation
of
tetrabromobisphenol A with graphene single bond BiFeO3
composite as a catalyst, Chem. Eng. J., 2013, 219, 225–237;
(b) Z. Li, Y. Shen, C. Yang, Y. Lei, Y. Guan, Y. Lin, D. Liu
and C. W. Nan, Signicant enhancement in the visible
light photocatalytic properties of BiFeO3-graphene
nanohybrids, J. Mater. Chem. A, 2013, 1, 823–829.
15 O. P. Bajpai, S. Mandal, R. Ananthakrishnan, P. Mandal,
D. Khastgir and S. Chattopadhyay, Structural features,
magnetic properties and photocatalytic activity of bismuth
ferrite nanoparticles graed on graphene nanosheets, New
J. Chem., 2018, 42, 10712–10723.
6 G. Liao, J. Fang, Q. Li, S. Li, Z. Xu and B. Fang, Ag-Based 16 (a) X. Qi, J. Dho, R. Tomov, M. G. Blamire and
nanocomposites: synthesis and applications in catalysis,
Nanoscale, 2019, 11, 7062–7096.
J. L. M. Driscoll, Greatly reduced leakage current and
conduction mechanism in aliovalent-ion-doped BiFeO3,
Appl. Phys. Lett., 2005, 86, 062903–062905; (b) C. C. Chen,
Z. X. Liu, G. Wang and Y. L. Yan, Pr and Gd co-doped
bismuth ferrite thin lms with enhanced multiferroic
properties, Bull. Mater. Sci., 2014, 37, 1725–1729.
7 G. Liao, Y. Gong, L. Zhang, H. Gao, G.-J. Yang and B. Fang,
Semiconductor polymeric graphitic carbon nitride
photocatalysts: the “holy grail” for photocatalytic hydrogen
evolution reaction under visible light, Energy Environ. Sci.,
2019, DOI: 10.1039/c9ee00717b.
8 K. Reilly, B. Fang, F. Taghipour and D. P. Wilkinson,
Enhanced photocatalytic hydrogen production in a UV-
irradiated uidized bed reactor, J. Catal., 2017, 353, 63–73.
17 F. Sabeen, S. A. Irfan, M. Z. Iqbal and S. Rizwan, The high
photocatalytic activity and reduced band gap energy of La
and Mn-doped/graphene nanoplatelet (GNP) nanohybrids,
RSC Adv., 2017, 7, 35928–35937.
9 R. Marschall, Photocatalysis: Semiconductor Composites: 18 H. Z. Qiang, M. Li, Y. Yu, J. Liu, L. Pei, J. Wang, X. Liu, B. Yu
Strategies for Enhancing Charge Carrier Separation to
Improve Photocatalytic Activity, Adv. Funct. Mater., 2014,
24, 2421–2440.
and X. Zhao, Effects of Nd and high valence Mn co-doping on
the electrical and magnetic properties of BiFeO3 ceramic,
Solid State Commun., 2010, 150, 1088–1091; A. Kudo and
Y. Miseki, Heterogeneous photocatalyst materials for water
splitting, Chem. Soc. Rev., 2009, 38, 253–278; M. Hoffmann,
S. Martin, W. Choi and D. Bahnemann, Environmental
applications of semiconductor photocatalysis, Chem. Rev.,
1995, 95, 69–96.
10 (a) J. Tang, J. R. Durrant and D. R. Klug, Mechanism of
photocatalytic water splitting in TiO2. Reaction of water
with photoholes, importance of charge carrier dynamics,
and evidence for four-hole Chemistry, J. Am. Chem. Soc.,
2008, 130, 13885–13891; (b) A. Kudo and Y. Miseki,
Heterogeneous photocatalyst materials for water splitting, 19 S. A. Ansari and M. H. Cho, Highly visible light responsive,
Chem. Soc. Rev., 2009, 38, 253–278; (c) M. Hoffmann,
S. Martin, W. Choi and D. Bahnemann, Environmental
applications of semiconductor photocatalysis, Chem. Rev.,
1995, 95, 69–96.
narrow band gap TiO2 nanoparticles modied by
elemental red phosphorus for photocatalysis and
photoelectrochemical applications, Sci. Rep., 2016, 6,
25405–25414.
11 W.-K. Jo and R. J. Tayade, New Generation Energy-Efficient 20 S. Fatima, S. I. Ali, D. Younas, A. Islam, D. Akinwande and
Light Source for Photocatalysis: LEDs for Environmental
S. Rizwan, Graphene nanohybrids for enhanced catalytic
Applications, Ind. Eng. Chem. Res., 2014, 53, 2073–2084.
17154 | RSC Adv., 2019, 9, 17148–17156
This journal is © The Royal Society of Chemistry 2019

View Article Online
Paper
RSC Advances
activity and large surface area, MRS Commun., 2018, 194, 1– 33 G. Singh and L. N. K. Verma, Magnetoelectric coupling in
10.
multiferroic Tb-doped BiFeO3 nanoparticles, Mater. Lett.,
2013, 111, 55–58.
21 E. Vasilaki, I. Georgaki, D. Vernardou, M. Vamvakaki and
N. Katsarakis, Ag-loaded TiO2/reduced graphene oxide 34 Y. B. Yao and C. L. Mak, Optical, ferroelectric and magnetic
nanocomposites for enhanced visible-light photocatalytic
activity, Appl. Surf. Sci., 2015, 353, 865–872.
22 W. Zhong, W. Tu, S. Feng and A. Xu, Photocatalytic H2
properties of multiferroelectric BiFeO3–(K0.5Na0.5 0.4
(Sr0.6Ba0.4 0.8Nb2O6 thin lms, J. Alloys Compd., 2014, 586,
448–455.
)
)
evolution on CdS nanoparticles by loading FeSe nanorods 35 A. Ganguly, S. Sharma, P. Papakonstantinou and
as co-catalyst under visible light irradiation, J. Alloys
Compd., 2019, 772, 669–674.
23 L. Pai, Q. Chen, Y. Lin, G. Chang and Y. He, Effects of
J. Hamilton, Probing the Thermal Deoxygenation of
Graphene Oxide Using High-Resolution In Situ X-ray-Based
Spectroscopies, J. Phys. Chem. C, 2011, 115, 17009–17019.
crystalline structure and interface band alignment on the 36 S. Chauhan, M. Kumar, S. Chhoker, S. C. Katyal and
photocatalytic property of bismuth ferrite/(N-doped)
graphene composites, J. Alloys Compd., 2016, 672, 497–504.
24 F. Zhang, G. Randhorn, L. Chanman, A. Linda, S. T. J. Irvine
M. Singh, Substitution driven structural and magnetic
transformation in Ca-doped BiFeO3 nanoparticles, RSC
Adv., 2016, 6, 43080–43090.
and K. J. R. Peter, Assessment of oxidative visible light and 37 S. C. Das, S. Katiyal and T. Shripathi, Impedance
UV active photocatalysts by hydroxyl radical quantication,
J. Photochem. Photobiol., A, 2017, 334, 13–19.
spectroscopy of Bi-rich BiFeO3: twin thermal-activations, J.
Appl. Phys., 2018, 124, 174101–174105.
25 J. F. Dai, T. Xian, L. J. Di and H. Yang, Preparation of BiFeO3- 38 M. F. Sunding, K. Hadidi, S. Diplas, O. M. Løvvik, T. E. Norby
Graphene
Nanocomposites
and
Their
Enhanced
and A. E. Gunnæs, XPS characterisation of in situ treated
lanthanum oxide and hydroxide using tailored charge
referencing and peak tting procedures, Fuel and Energy
Abstracts, 2011, 184, 399–409.
Photocatalytic Activities, J. Nanomater., 2013, 2013,
642897–642901.
26 S. Irfan, L. L. Li, A. S. Saleemi and C.-W. Nan, Enhanced
photocatalytic activity of La3+ and Se4+ co-doped bismuth 39 S. Chen, B. Pan, L. Zeng, S. Luo, X. X. Wang and W. Su,
ferrite nanostructures, J. Mater. Chem. A, 2017, 5, 11143–
11151.
27 F. Gao, X. Chen, K. Yin, S. Dong, Z. F. Ren, F. Yuan, T. Yu,
La2Sn2O7 enhanced photocatalytic CO2 reduction with H2O
by deposition of Au co-catalyst, RSC Adv., 2017, 7, 14186–
14191.
Z. G. Zou and J. M. Liu, Visible-light photocatalytic 40 M. Wanwan, R. Hu, J. Yang, Y. Du, J. Li and H. Wang,
properties of weak magnetic BiFeO3 nanoparticles, Adv.
Mater., 2007, 19, 2889–2892.
28 R. Guo, L. Fang, W. Dong, F. Zheng and M. Shen,
Inuence of lanthanum-doping on photocatalytic
properties of BiFeO3 for phenol degradation, Chin. J.
Catal., 2016, 37, 1283–1292.
Magnetically separable BiFeO3 nanoparticles with a g- 41 R. Das, T. Sarkar and K. Mandal, Multiferroic properties of
Fe2O3 parasitic phase: controlled fabrication and enhanced
visible-light photocatalytic activity, J. Mater. Chem., 2011,
21, 18645–18652; C. Reitz, C. Suchomski, C. Weidmann
Ba2+ and Gd3+ co-doped bismuth ferrite: magnetic,
ferroelectric and impedance spectroscopic analysis, J. Phys
D Appl. Phys., 2012, 45, 455002–455005.
and T. Brezesinski, Block copolymer-templated BiFeO3 42 M. Shenasa, S. Sainkar and D. Lichtman, XPS study of some
nanoarchitectures composed of phase-pure crystallites
intermingled with a continuous mesoporosity: effective
visible-light photocatalysts, Nano Res., 2011, 4, 414–424.
29 C. P. Kumar and M. Kar, Effect of rhombohedral to
orthorhombic transition on magnetic and dielectric
properties of La and Ti co-substituted BiFeO3, Smart Mater.
Struct., 2015, 24, 045028–045031.
30 Y. Y. Gurkan, E. Kasapbasi and Z. Cinar, Enhanced solar
photocatalytic activity of TiO2 by selenium (IV) ion-doping:
Characterization and DFT modeling of the surface, Chem.
Eng. J., 2013, 214, 34–44.
selected selenium compounds, J. Electron Spectrosc. Relat.
Phenom., 1986, 40, 329–337.
43 Y. Li, Y. Zhang, W. Le, J. Yu, C. Lu and L. Xia, Photo-to-
current response of Bi2Fe4O9 nanocrystals synthesized
through a chemical co-precipitation process, New J. Chem.,
2012, 36, 1297–1300.
44 X. Y. Guan, Z. W. Qiao and D. Z. Yan, Investigation on
structural and functional properties of Nd doped BiFeO3
particles prepared by hydrothermal method, J. Mater. Sci.:
Mater. Electron., 2015, 26, 6807–6810.
45 M. Sero and J. Bisquert, Fermi level of surface states in TiO2
nanoparticles, Nano Lett., 2003, 3, 945–948.
31 P. Tang, D. Kuang, S. Yang and Y. Zhang, The structural, optical
and enhanced magnetic properties of Bi1-xGdxFe1-yMnyO3 46 P. Vanga, R. Mangalaraja and M. Ashok, J. Mater. Sci.: Mater.
nanoparticles synthesized by sol-gel, J. Alloys Compd., 2015,
622, 194–199.
32 R. Palai, R. S. Katiyar, H. Schmid, P. Tissot, S. J. Clark,
J. Robertson, S. A. T. Redfern, G. Catalan and J. F. Scott, b-
phase and g-b metal-insulator transition in multiferroic
Electron., 2016, 27, 5699–5706.
47 X. S. Xu, T. V. Brinzari, S. Lee, Y. H. Chu, L. W. Martin,
A. Kumar and S. W. Cheong, Optical properties and
magnetochromism in multiferroic BiFeO3, Phys. Rev. B:
Condens. Matter Mater. Phys., 2009, 79, 134425–134433.
BiFeO3, Phys. Rev. B: Condens. Matter Mater. Phys., 2008, 48 W. Zhong, Z. Lin, S. Feng, D. Wang, S. Shen, Q. Zhang, L. Gu,
77, 014110–014121.
Z. Wand and B. Feng, Improved Oxygen Evolution Activity of
This journal is © The Royal Society of Chemistry 2019
RSC Adv., 2019, 9, 17148–17156 | 17155

View Article Online
RSC Advances
Paper
IrO2 by in situ Engineering of Ultra-Small Ir Sphere Shell 56 J. P. Xu, R. J. Zhang, Z. H. Chen, Z. Y. Wang, F. Zhang, X. Yu
Utilizing Pulse Laser, Nanoscale, 2019, 11, 4407–4413.
49 Y. Liu, S. Shen, J. Zhang, W. Zhong and X. Huang, Cu2ꢀxSe/
CdS composite photocatalyst with enhanced visible light
photocatalysis activity, Appl. Surf. Sci., 2019, 478, 762–769.
50 W. Zhong, S. Shen, S. Feng, Z. Lin, Z. Wanga and B. Fang,
Facile fabrication of alveolate Cu2ꢀxSe microsheets as
and L. Y. Chen, Optical properties of epitaxial BiFeO3 thin
lm grown on SrRuO3-buffered SrTiO3 substrate, Nanoscale
Res. Lett., 2014, 9, 188–194.
57 S. Irfan, S. Rizwan, Y. Shen, R. Tomovska, S. Zulqar,
M. I. Sarwar and C. W. Nan, Mesoporous template-free
gyroid-like nanostructure based on La and Mn co-doped
bismuth ferrites with improved photocatalytic activity, RSC
Adv., 2016, 115, 114183–114189.
a
new visible-light photocatalyst for discoloration of
Rhodamine B, CrystEngComm, 2018, 20, 7851–7856.
51 Z. Zhang, H. Liu, Y. Lin, Y. Wei, Ce-W. Nan and X. Deng, 58 M. Sakar, B. Subramanian, I. Bhaumik, P. K. Gupta and
Inuence of La Doping on Magnetic and Optical Properties
of Bismuth Ferrite Nanobers, Nanomaterials, 2012,
238605, 1–5.
S. N. Jaisankar, Nanostructured Bi1-xGdxFeO3 – multiferroic
photocatalyst on its sunlight driven photocatalytic activity,
RSC Adv., 2014, 32, 16871–16878.
52 N. Zhang, D. Chen, F. Niu, S. Wang, L. Qin and Y. Huang, 59 S. Irfan, S. Rizwan, Y. Shen, L. Li, S. Butt and C. W. Nan, The
Enhanced visible light photocatalytic activity of Gd-doped
BiFeO3 nanoparticles and mechanism insight, Sci. Rep.,
2016, 6, 26467–26476.
gadolinium (Gd3+ and Tin (Sn4+) co-doped BiFeO3
)
Nanoparticles as new solar light active photocatalyst, Sci.
Rep., 2017, 7, 42493–42505.
53 F. Mushtaq, X. Z. Chen, M. Hoop, H. Torlakcik, E. Pellicer, 60 W. Choi, A. Termina and M. R. Hoffman, The role of metal
J. Sort, C. Gattinoni, B. J. Nelson and S. Pane,
Piezoelectrically Enhanced Photocatalysis with BiFeO3
Nanostructures for Efficient Water Remediation, iScience,
2018, 4, 236–246.
ion dopants in quantum-sized TiO2: correlation between
photoreactivity and charge carrier recombination
dynamics, J. Phys. Chem., 1994, 98, 13669–13679.
61 C. Yongjuan, H. Ge, L. Wei, Z. Li, R. Yuan, P. Liu and X. Fu,
Reduction degree of reduced graphene oxide (RGO)
dependence of photocatalytic hydrogen evolution
performance over RGO/ZnIn2S4 nanocomposites, Catal. Sci.
Technol., 2013, 7, 1712–1717.
54 Y. Huo, Y. Jin and Y. Zhang, Citric acid assisted solvothermal
synthesis of BiFeO3 microspheres with high visible-light
photocatalytic activity, J. Mol. Catal. A: Chem., 2010, 331,
15–20.
55 P. Kubelka and F. Munk, Ein Beitrag zur Optik der 62 A. Iwase, Y. H. Ng, Y. Ishiguro, A. Kudo and R. Amal,
Farbanstriche (contribution to the optic of paint), Z. Phys.,
1931, 12, 593–601.
Reduced graphene oxide as a solid-state electron mediator
in Z-scheme photocatalytic water splitting under visible
light, J. Am. Chem. Soc., 2011, 133, 11054–11057.
17156 | RSC Adv., 2019, 9, 17148–17156
This journal is © The Royal Society of Chemistry 2019