Hydrothermal fabrication and characterization of ZnO/Fe2O3 heterojunction devices for hydrogen production

Abstract

ZnO/Fe 2 O 3 heterojunction were prepared by sequentially depositing iron oxide α-Fe 2 O 3 and zinc oxide ZnO films on FTO (SnO 2 :F) substrates. The α-Fe 2 O 3 and ZnO films and the α-Fe 2 O 3 / ZnO heterojunction were characterized by Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDX), and X-Ray Diffraction (XRD). Pure crystalline ZnO films were hydrothermally deposited on α-Fe 2 O 3 films and the process parameters were as follows: hydrothermal time, 4h; temperature 150°C. Finally, the device was transferred to an electric oven and heated at a constant temperature of 90°C for 5h, to develop the ZnO nanostructure. The photocurrent measurements showed an increase of the intrinsic surface states or defects at the α-Fe 2 O 3 /ZnO interface. The photoelectrochemical performance of the α-Fe 2 O 3 /ZnO heterojunction was examined by chronoamperometry and linear sweep voltammeter techniques. It was found that the α-Fe 2 O 3 /ZnO structure exhibits a higher photoelectrochemical activity when compared to α-Fe 2 O 3 thin films. The highest photocurrent density was obtained for α-Fe 2 O 3 /ZnO films in 1 M NaOH electrolyte. This high photoactivity was attributed to the high active surface area and to the external applied bias, which favors the transfer and the separation of the photogenerated charge carriers in α-Fe 2 O 3 /ZnO heterojunction devices.

Effect of Cu, Ni and Pb doping on the photo-electrochemical activity of ZnO thin films

“…The overall PEC reaction can be represented as 2H 2 O / 2H 2 + O 2 (DE ¼ À1.23 V/RHE). 21 Since H 2 O oxidation is the rate-limiting reaction in the overall PEC water splitting, the design of an efficient photoanode is an important barrier to overcome to perform this reaction. 22 For efficient PEC water splitting, ZnO is a prominent semiconductor owing to its low cost and high catalytic efficiency.…”

“…They got maximum photoconversion efficiency (2.7%) under solar irradiation of 100 mW cm À2 for PEC hydrogen generation using the electrode grown for 3 h. The maximum hydrogen rate was 22 mL cm À2 aer 1 h exposure. Moreover, Bouhjar et al 21,28 showed that the PEC efficiency of the hydrothermally grown a-Fe 2 O 3 /ZnO heterojunction is higher than that of FTO/a-Fe 2 O 3 and FTO/ZnO. Furthermore, Kim et al 29 introduced complex co-sensitized ZnO/WO x heterostructures for efficient visible light absorption and PEC hydrogen production.…”

New Approaches to Increasing the Superhydrophobicity of Coatings Based on ZnO and TiO2

“…The correlation between temperature and composition of nitrogen plasma can be carried out in accordance with the kinetic model proposed in [10]. It can be estimated that during the transition from mode M to mode A with an increase in the average mass temperature from 4÷6 to 8÷10 kK, the molecular component of nitrogen plasma significantly decreases.…”

“…In particular, the Teflon-AF grade (DuPont, Wilmington, DE, USA) used in [9] has a decomposition temperature of 360 • C. Complex and expensive equipment is required to obtain a polymer coating with good adhesion to the sample surface and thermal stability. On the other hand, complexes of materials possessing high functionality, in particular, ZnO/Au, ZnO/Fe 2 O 3 , are effective selective gas sensors and photocatalysts [10]. In this work, it is proposed to coat ZnO with non-polar inorganic materials with high heat resistance and good adhesion to ZnO, for example Au and Fe 2 O 3, to increase superhydrophobicity.…”

Nanoscale ZnO/α‐Fe2O3 Heterostructures: Toward Efficient and Low‐Cost Photoanodes for Water Splitting

“…Moreover, the overall enhancement in the photocurrent density can be also attributed to the improved light harvesting ability of the material itself, coming from the adequate band‐edge alignment of the two semiconductors involved in the formation of the heterostructure. [ 154 ]…”