Supplementary Information
Effect of Syntheses methods on the Physico-Chemical
properties of a ZnFe2O4 photocatalyst
Rekha Dom1,2, A.Sadananda Chary2, R.Subasri1, Neha Y.Hebalkar1 and Pramod H. Borse1*
1International
Advanced Research Centre for Powder Metallurgy and New Materials
Balapur PO, Hyderabad, AP, 500 005, India
2
Department of Physics, University college of Science, Osmania University, Hyderabad,
AP,India.500007.
Corresponding Author: Dr. P.H.Borse; Email: phborse@arci.res.in;
Tel.: 914024452426; Fax: 914024442699
X-ray diffraction spectra of ZnFe2O4 photocatalysts obtained by
different synthesis methods
Fig.S.I.1.XRD spectra of ZnFe2O4 samples synthesized by SSR method at different temperatures
(a)
(b)
Fig.S.I.2.XRD spectra of ZnFe2O4 samples synthesized by PC method for (a)different molar
concentrations of citric acid and (b)different calcination temperatures
(a)
(c)
(b)
(d)
Fig.S.I.3.XRD spectra of ZnFe2O4 samples synthesized by µW method at (a)different µW powers,
(b)irradiation temperatures and (c)time (d) Low power microwave(~1kW)
Fig.S.I.4.XRD spectra of ZnFe2O4 samples synthesized by SPC method for different ratios of
Zn:Fe:glycine
Photostability of ZnFe2O4 photocatalysts
Fig.S.I.5.XRD spectra of ZFO particles synthesized by different methods before and after
photocatalytic reaction.
Electro-chemical Characterization
Inorder to perform measurements shown in Fig.S.I. 7, the following procedure was followed.
ZnFe2O4 -photocatalyst powders obtained by different synthesis methods were coated on
Flourine-doped Tin oxide (FTO) glass substrates to be used as working electrodes for
electrochemical characterization. The FTO substrates were cleaned thoroughly and sonicated in
de-ionized water and organic liquids for long time prior to coating. The ZFO powders to be
coated were thoroughly mixed with the appropriate binder (PEG) and the paste was coated on the
substrates using the Doctor-blade technique (Reference: Suk Joon Hong, Hwichan Jun, Pramod
H. Borse, Jae Sung Lee, International journal of hydrogen energy, 2009, 34, 3234–3242). A
small area of the substrate was left uncoated to make contacts for the electrode fabrication. Thus
obtained films were dried in air and then calcined in furnace at 4500C at the rate of 20C/min for
1hr. The films were then fabricated into electrodes using Cu wire. High purity Ag paste was used
to make contacts with the wire. The electrode was then sealed properly leaving only the portion
of deposited area for measurements.
The electrochemical characterization was carried out using a conventional 3-electrode cell, using
a Pt plate as counter electrode and Ag/AgCl electrode (3MNaCl) as reference electrode. The
electrolyte was 1Molar NaOH aqueous solution at pH~13.6. ZnFe2O4 powders coated on FTO
glass substrates of area 1X1cm2were used as working electrode. The electrochemical
measurements were recorded using electrochemical workstation (PARSTAT –Model 2273) with
a built in frequency response detector (Model-1025). The Mott-Schottky plots were recorded in
dark at an applied frequency of 10kHz and 10mV Ac voltage. The electrochemical impedance
spectra for different electrodes were recorded at an applied dc voltage of 0.6V(vs.Ag/AgCl) in
the frequency range 100mHz-1MHz.
The impedance measurements allow the derivation of capacitance at the semiconductorelectrolyte- interface, which can be described by a Mott-Schottky (MS) plot (i.e. graph of 1/C2 vs
V). The Mott-Schottky equation is described by relationship
1
2
=
(V ~ V )
2
2
fb
C
(ε ε eN S ) b
sc
0 s D
εsis the dielectric constant of the semiconductor 100
ε0 is the vacuum permittivity and is 8.85 X 10-12C2/Nm2
ND is the Donor density and S the surface area of the electrode in cm2.
Fig.S.I.6.Mott-Schottky plots of ZnFe2O4 powders synthesized by different methods