Water-soluble peroxotitanium complex: A novel strategy to prepare Fe2O3/Fe2TiO5 photoanode with enhanced water oxidation

Improved Water Oxidation of Fe2O3/Fe2TiO5 Photoanode by Functionalizing with a Hydrophilic Organic Hole Storage Overlayer

“…For the Fe 2 O 3 /Fe 2 TiO 5 sample, the C 1s spectrum is deconvoluted into three peaks, attributed to C–C (284.8 eV), C–O (286.4 eV), and CO (288.1 eV) species, respectively. , By comparison, there is an additional fitted peak at 285.4 eV in the C 1s spectrum of the HEDP-Fe 2 O 3 /Fe 2 TiO 5 photoanode, originating from the C–P–O bond of the HEDP molecule. , The O 1s spectra are displayed in Figure d, wherein the Fe 2 O 3 /Fe 2 TiO 5 photoanode exhibits two kinds of oxygen species: lattice oxygen (O 2– ) for Fe 2 O 3 /Fe 2 TiO 5 (529.6 eV) and surface-adsorbed oxygen such as OH – and a water molecule (531.1 eV). , For the HEDP-Fe 2 O 3 /Fe 2 TiO 5 film, three overlapping components at 530.1, 531.3, and 532.9 eV are clearly observed, assigned to the lattice oxygen of Fe 2 O 3 /Fe 2 TiO 5 , P–O bonds, and adsorbed water, respectively. , Obviously, the presence of P–O bonds further declares the successful HEDP deposition. In Figure e, the high-resolution Fe 2P XPS of Fe 2 O 3 /Fe 2 TiO 5 and HEDP-Fe 2 O 3 /Fe 2 TiO 5 photoanodes show two spin–orbit peaks of Fe 2p 2/3 and Fe 2p 1/2 , and their binding energies are in accord with the typical values of Fe 3+ species in hematite. − Regarding the Ti 2p XPS spectra (Figure f), the characteristic peaks of Ti 2p 3/2 and Ti 2p 1/2 of both photoanodes also agree well with those of Ti 4+ species. , More notably, in comparison with the Fe 2 O 3 /Fe 2 TiO 5 sample, the HEDP-Fe 2 O 3 /Fe 2 TiO 5 photoanode exhibits an obvious positive shift in the binding energies of O 1s (O 2– species), Fe 2p, and Ti 2p peaks. The shift might be attributed to the Fermi level shift or the nonlinear response of the XPS spectrometer.…”

“…24−26 Regarding the Ti 2p XPS spectra (Figure 3f), the characteristic peaks of Ti 2p 3/2 and Ti 2p 1/2 of both photoanodes also agree well with those of Ti 4+ species. 10,24 More notably, in comparison with the Fe 2 O 3 / Fe 2 TiO 5 sample, the HEDP-Fe 2 O 3 /Fe 2 TiO 5 photoanode exhibits an obvious positive shift in the binding energies of O 1s (O 2− species), Fe 2p, and Ti 2p peaks. The shift might be attributed to the Fermi level shift or the nonlinear response of the XPS spectrometer.…”

“…To further confirm the essential role of the HEDP overlayer, M-S and EIS characterizations for Fe 2 O 3 /Fe 2 TiO 5 and HEDP-Fe 2 O 3 /Fe 2 TiO 5 samples were performed. The M-S plots conducted in the dark condition are shown in Figure S13, in which the positive slopes for Fe 2 O 3 /Fe 2 TiO 5 and HEDP-Fe 2 O 3 /Fe 2 TiO 5 films indicate that both samples exhibit an n-type character with the electrons as majority carriers. , Moreover, according to these slopes, the carrier densities of both photoanodes are determined to follow the equation in the Supporting Information. The calculation results reveal that the HEDP-Fe 2 O 3 /Fe 2 TiO 5 photoanode exhibits a similar donor density (4.72 × 10 20 cm –3 ) as that for the Fe 2 O 3 /Fe 2 TiO 5 sample (3.53 × 10 20 cm –3 ), indicating that the HEDP overlayer mainly alters the surface properties without an obvious effect on the bulk electrode.…”

“…The Fe 2 O 3 /Fe 2 TiO 5 photoanode was fabricated through a modified hydrothermal process reported in our previous study. 24 In brief, 80 mL of an aqueous solution that contained 75 mM iron chloride hexahydrate (FeCl 3 •6H 2 O) and 50 mM glucose (C 6 H 12 O 6 ) was first prepared and then transferred into a 100 mL Teflon-lined autoclave. After that, a precleaned fluorine-doped tin oxide (FTO) glass (5 × 3 × 0.16 cm, less than 15 ohm sq −1 , Wuhan Jinge Solar Energy Technology Co., Ltd.) was placed into the sealed autoclave for the hydrothermal reaction at 100 °C for 4 h. Thereafter, the as-obtained FeOOH film was rinsed with deionized (DI) water and soaked into a peroxotitanium complex (PTC) solution (6.46 mM, 10 mL) for a sonication of 5 min.…”

“…The Fe 2 O 3 /Fe 2 TiO 5 photoanode was fabricated through a modified hydrothermal process reported in our previous study . In brief, 80 mL of an aqueous solution that contained 75 mM iron chloride hexahydrate (FeCl 3 ·6H 2 O) and 50 mM glucose (C 6 H 12 O 6 ) was first prepared and then transferred into a 100 mL Teflon-lined autoclave.…”