Fabrication of CuFe₂O₄/α-Fe₂O₃ Composite Thin Films on FTO Coated Glass and 3-D Nanospike Structures for Efficient Photoelectrochemical Water Splitting

Abstract

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.