Photocurrent Enhancement for Ti-Doped Fe₂O₃ Thin Film Photoanodes by an In Situ Solid-State Reaction Method

Abstract

In this work, a higher concentration of Ti ions are incorporated into hydrothermally grown Ti-doped (2.2% by atomic ratio) micro-nanostructured hematite films by an in situ solid-state reaction method. The doping concentration is improved from 2.2% to 19.7% after the in situ solid-state reaction. X-ray absorption analysis indicates the substitution of Fe ions by Ti ions, without the generation of Fe²⁺ defects. Photoelectrochemical impedance spectroscopy reveals the dramatic improvement of the electrical conductivity of the hematite film after the in situ solid-state reaction. As a consequence, the photocurrent density increases 8-fold (from 0.15 mA/cm² to 1.2 mA/cm²), and it further increases up to ∼1.5 mA/cm² with the adsorption of Co ions. Our findings demonstrate that the in situ solid-state reaction is an effective method to increase the doping level of Ti ions in hematite films with the retention of the micro-nanostructure of the films and enhance the photocurrent.

A Synergistic Effect of Surfactant and ZrO2 Underlayer on Photocurrent Enhancement and Cathodic Shift of Nanoporous Fe2O3 Photoanode

“…Relatively high C ss value for FZC sample indicates that the multiplied influxes of holes (available for charge transfer to the electrolyte) are driven by the large nanoporous architecture of Fe 2 O 3 photoanode. Higher C ss value is consistent with the cathodic shift in V onset for Fe 2 O 3 films43. In our previous study, it is shown that higher crystalline orientation along (104) plane is consistent with the higher degree of surface states, which resulted in higher C ss value37.…”

“…Thus, large number of accumulated holes facilitates the water oxidation process leading to early photocurrent onset (as seen from PEC study). Miao et al observed higher C ss value, which is consistent with the cathodic shift in V onset of Fe 2 O 3 films43. Recently, Li et al showed prominent PEC performance for hematite nanorods consisting a thin amorphous TiO 2 layer (as a defect-creating layer) and the improvement is attributed to the accelerated hole-transfer via surface trap at the hematite-electrolyte interface45.…”

“…Low charge transfer resistance ( R ct ) for FZC (Table 1) can primarily be interpreted by a significantly enhanced conductivity in Fe 2 O 3 due to doping: largely due to Sn 4+ ions (from FTO) and partially due to Zr 4+ ions (from ZrO 2 UL). It also meant that nanoporous architecture of the film helped facilitate the charge transfer of holes to the electrolyte species efficiently leading to the photocurrent improvement43. The surface state capacitance ( C ss ) governs the presence of surface or defect states (whose chemical identity is Fe-O*) that are formed due to oxygen vacancies17.…”

Iron‐Based Supercapacitor Electrodes: Advances and Challenges

“…[85][86][87][88] Lately, Lu et al demonstrated the conductivity and capacitive properties of α-Fe 2 O 3 NRs could be remarkably boosted after introducing oxygen vacancies through a simple and effective method. [85][86][87][88] Lately, Lu et al demonstrated the conductivity and capacitive properties of α-Fe 2 O 3 NRs could be remarkably boosted after introducing oxygen vacancies through a simple and effective method.…”

Effect of Zn Concentration on Microstructural, Optical, and Hyperfine Properties of Nanocrystalline α-Fe2O3

“…Spins in hematite are slightly canted away from antiferromagnetic (AFM) orientation on the basal plane, giving place to the weakly ferromagnetic (FM) state, between the Morin temperature T M \260 K and the Neel temperature T N \956 K, but the spins are oriented along the [111] axis and perfectly antiferromagnetic below T M [12]. There are a number of reports on the photo-catalytic activity and water splitting properties of a-Fe 2 O 3 nanoparticles by doping suitable dopants [13][14][15][16].…”