Enhanced visible light photoelectrochemical water splitting using nanotubular FeOx-TiO2 annealed at different temperatures

Photoelectrochemical Performance of Nanotubular Fe2O3–TiO2 Electrodes under Solar Radiation

“…Figure 4 displays the Raman spectra acquired for hybrid Fe 2 O 3 –TiO 2 samples obtained by electrodeposition for 5–120 s (A) and 180 s (B). Regardless of the amount of hematite obtained after annealing, all samples are composed of anatase and hematite, as manifested by Raman bands for TiO 2 at 150, 399, 519, and 638 cm −1 [ 25 , 28 ] as well as for α-Fe 2 O 3 at 220, 284, and 1318 cm −1 [ 27 ]. In turn, an intensity ratio of the α-Fe 2 O 3 and TiO 2 bands clearly shows that the content of hematite gradually increases, and only these iron species are formed when anodic TiO 2 is subjected to electrodeposition of up to 60 s. The intensity of the α-Fe 2 O 3 features varies slightly across the sample surface, indicating that its growth is uneven ( Figure S2, Supplementary Materials ).…”

“…After 120 s, additional low- and medium-intensity Raman bands appear at ca. 230 (goethite, FeOOH), 390/500 (maghemite, γ-Fe 2 O 3 ), 610 (wüstite, FeO), 660 (magnetite, Fe 3 O 4 ), and 1300 (lepidocrocite, γ-FeO(OH)) cm −1 ( Figure 4 A) [ 28 ]. The distribution of these iron oxides changes due to the elongation of the deposition time up to 180 s ( Figure 4 B).…”

“…For all studied samples, optical band gap values were determined from diffuse reflectance measurements, as described previously [ 27 , 28 ]. An example of the estimation of the optical band gap energy from UV-Vis DRS measurements is presented in Figure S3 in Supplementary Materials .…”

“…As the reference sample, an anodic TiO 2 layer impregnated with 100 mM FeCl 3 (Honeywell, Seelze, Germany) ( Figure 1 A1) and annealed at 450 °C for 2 h ( Figure 1 A2) was used. The experimental details have been described previously [ 27 , 28 ].…”

“…Moreover, the PEC water-splitting experiments were carried out under solar and monochromatic illumination. The obtained results were compared with a similar material received by impregnation of anodic titanium oxide in a 100 mM FeCl 3 solution, the full characterization of which was previously reported [ 27 , 28 ]. Furthermore, the synthesized materials were also tested for the first time as potential non-enzymatic PEC sensors for the determination of glucose.…”