Abstract
In this research, three different sets of hematite (α-Fe2O3) films of various thicknesses were prepared using dip, spin, and combined dip/spin coating methods. α-Fe2O3films of 450–500, 740–800 and 920–980 ± 30 nm thicknesses were prepared using each of the coating methods, and their photoelectrochemical (PEC) behaviour was investigated. Dip coated films produced the best photoresponse while the films prepared using the spin coating method yielded the least photocurrent values across films of different thicknesses. Maximum photocurrent densities of 34.6, 7.8, and 13.5 μA/cm2V vs reversible hydrogen electrode (RHE) were obtained for the dip, spin and combined dip/spin coated films with a thickness of 740–800 ± 30 nm respectively. Improved crystallization, low charge transfer resistance at the α-Fe2O3/electrolyte interface, high surface states capacitance and the more negative flat band potential values obtained for dip coated films have been associated with the enhanced photocurrent response recorded for the films. The preferential crystal growth of spin coated films in the (104) plane associated with low electron mobility and the high resistance to charge transfer at the α-Fe2O3/electrolyte interface of the films is largely responsible for their low photoresponse. This study underscores the significance of simultaneously optimizing both coating techniques for film deposition and the film’s thickness in preparing nanostructured α-Fe2O3films for PEC applications.
Highlights
The shot hole diffusion length of (2–4) nm (Kim et al, 2013) for α-Fe2O3 which results in high recombination rate of electron-hole pairs during PEC applications is among the top challenges limiting its efficiency
Three different sets of α-Fe2O3 films were prepared using dip, spin, and combined dip/spin coating techniques and their PEC properties were investigated. α-Fe2O3 films of 450–500, 740–800 and 920–980 ± 30 nm thicknesses were prepared using each of the coating methods respectively, to get a better perspective on the influence of both coating techniques and film thickness on the PEC behaviour of the films
The PEC behaviour of α-Fe2O3 films prepared using dip, spin and combined dip-spin coating methods have been investigated. α-Fe2O3 films of 450–500, 740–800 and 920–980 ± 30 nm thicknesses were prepared using each of the coating methods to obtain a clear perspective on the influence of both film thickness and coating techniques on the PEC response of the films
Summary
Α-Fe2O3, the most stable phase of iron oxide has found applications in numerous fields including gas sensing (Hjiri, 2020), medicine (Rajendran et al, 2015; Naz et al, 2019), magnetic recording (Jalli et al, 2010), and PEC water splitting (Kim et al, 2013; Feng et al, 2020; Reddy et al, 2020). Coating techniques were found to impact the absorption pattern and crystallization of α-Fe2O3 films prepared using the dip, spin and combined dip/spin coating method. Coating techniques can affect the crystallization as well as absorption pattern of α-Fe2O3 films which can have significant effect on their PEC response when used as a photocatalyst for water splitting. Another important parameter that can affect the PEC properties of α-Fe2O3 photoanodes is the film’s thickness. This study highlights the importance of simultaneously optimizing both the coating techniques for film deposition and the film’s thickness when preparing nanostructured α-Fe2O3 films for PEC water splitting
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