Recently, photoelectrochemical conversion
(PEC) of water into fuel is attracting great attention of researchers
due to its outstanding benefits. Herein, a systematic study on PEC
of water using CuFe2O4/ α–Fe2O3 composite thin films is presented. CuFe2O4/ α–Fe2O3 composite
thin films were deposited on two different substrates; (1) planner
FTO glass and (2) 3-dimensional nanospike (NSP). The films on both
substrates were characterized and tested as anode material for photoelectrochemical
water splitting reaction. During PEC studies, it was observed that
the ratio between two components of composite is crucial and highest
PEC activity results were achieved by 1:1 component ratio (CF-1) of
CuFe2O4 and α–Fe2O3. The CF-1 ratio sample deposited on planar FTO substrate
provided a photocurrent density of 1.22 mA/cm2 at 1.23 V
RHE which is 1.9 times higher than bare α–Fe2O3 sample. A significant PEC activity outperformance
was observed when CF-1 ratio composite thin films were deposited on
3D NSP. The highest photocurrent density of 2.26 mA/cm2 at 1.23 V
RHE was achieved for 3D NSP
sample which is around 3.6 times higher than photocurrent density
generated by α–Fe2O3 thin film
only. The higher photocurrent densities of 3D nanostructured devices
compared to planar one are attributed to the enhanced light trapping
and increased surface area for photoelectrochemical water oxidation
on the surface. The difference between valence and conduction bands
of CuFe2O4 and α–Fe2O3 allows better separation of photogenerated electrons
and holes at the CuFe2O4/ α–Fe2O3 interface which makes it more active for photoelectrochemical
water splitting.
In this work, we study the role of
nanotextured ZnFe2O4/Fe2O3composite thin films fabricated
by ultrasonic spray pyrolysis (USP) on the photoelectrochemical water
oxidation reactions. The ZnFe2O4/Fe2O3 composites with different molar ratios are deposited
on three-dimensional nanospikes (NSP) substrate, and the results are
compared with those for planar devices. It is observed that optical
absorption and charge separation due to larger surface area is significantly
enhanced in nanotextured photoactive ZnFe2O4/Fe2O3 films. After characterization of ZnFe2O4/Fe2O3 composite films
with different molar ratios (ZF1, ZF2, and ZF3), we find that the
nanotextured ZF1 composite with a molar ratio of 1:1 has the highest
activity with photocurrent density of 2.19 mA/cm2 in photoelectrochemical
oxidation of water. This photocurrent density is 3.4 and 2.73 times
higher than the photocurrent density values of pure hematite on planar
fluorine-doped tin oxide (FTO) coated glass and the highest reported
value of ZnFe2O4/Fe2O3 composite, respectively. In addition, the results of electrochemical
impedance spectroscopy (EIS) and photoluminescence (PL) tests indicate
lower charge transfer resistance and faster charge extraction for
the nanotextured ZnFe2O4/Fe2O3 composite (ZF1). Overall, our new fabrication process for
the ZnFe2O4/Fe2O3 composite
together with the effect of nanostructured substrate shows a better
charge separation and enhanced optical absorption, resulting in a
highly efficient photoelectrochemical water-splitting device.
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