Nanowheat-Like α-Fe₂O₃@Co-Based/Ti Foil Photoanode with Surface Defects for Enhanced Charge Carrier Separation and Photoelectrochemical Water Splitting

Abstract

Photoelectrochemical water splitting is an attractive and clean approach for hydrogen and oxygen evolution. The α-Fe2O3–H@CoO–H/Ti foil (TF) synthesized by two-step calcination process is used as a photoanode for solar to hydrogen energy. The scanning electron microscopy and transmission electron microscopy indicate the multi-level nanowheat-like structure with defects on the surface. It is favorable for light absorption and separation of the charge carrier. The crystal structure and composition were analyzed by the X-ray diffraction, Raman, X-ray fluorescence, and X-ray photoelectron spectroscopy studies. The photocurrent density of α-Fe2O3–H@CoO–H/TF is 1.60 mA/cm2 at 1.23 V versus reversible hydrogen electrode (RHE) and 14.63 mA/cm2 at 1.6 V versus RHE. The resistance and combination of the charge carrier at the interface of the photoanode/electrolyte and photoanode/TF are greatly decreased from electrochemical impedance spectroscopy. The collaborative improvement of the nanowheat-like morphology, residual little Co element as the oxygen evolution reaction catalyst, and oxygen vacancy in the surface defect after the hydrogen calcination are significant for photoelectrochemical water splitting.

Nanostructuring Bi-Doped α-Fe2O3 Thin-Layer Photoanode to Advance the Water Oxidation Performance

“…Consistently, a maximum ABPE value of 0.63% was obtained by the BF-5 photoanode at 0.86 V vs RHE, which significantly increased by almost 2.5 times compared to its pristine α-Fe 2 O 3 (Figure d). The obtained ABPE is comparable to the reported hematite photoanodes with Sn–Mg co-doped α-Fe 2 O 3 and nanowheat-like α-Fe 2 O 3 @Co-based/Ti-foil. , In addition, the pristine α-Fe 2 O 3 and BF thin-film photoanodes were further analyzed with a Hall-effect measurement. Figure e indicates the Hall-effect measurement results with the obtained properties of carrier concentration, carrier mobility, and conductivity.…”

“…The obtained ABPE is comparable to the reported hematite photoanodes with Sn− Mg co-doped α-Fe 2 O 3 and nanowheat-like α-Fe 2 O 3 @Cobased/Ti-foil. 61,62 In addition, the pristine α-Fe 2 O 3 and BF thin-film photoanodes were further analyzed with a Hall-effect measurement. Figure 4e indicates the Hall-effect measurement Further, there are fewer carrier concentrations in Bi-doped samples revealing that the photocarriers that resulted from photoactivities tend to be more active for surface reaction rather than recombining with the intrinsic carriers.…”

Recent Trends in Sustainable Solar Energy Conversion Technologies: Mechanisms, Prospects, and Challenges

“…Mechanistically, the absorption of light triggers charge separation in a semiconductor photocatalyst with the photogenerated electron transfer to the HER co-catalyst and a hole (h + ) migrating to the co-catalyst, where the OER takes place (panels a and b of Figure ). ,− Generally, photocatalysis involves oxidation of the substrate. The semiconductors with valence band (VB) oxidation potential greater than +2.7 V versus reversible hydrogen electrode (RHE) are able to produce very reactive oxygen radicals.…”

Cobalt-doped double-layer α-Fe2O3 nanorod arrays for enhanced photoelectrochemical reduction of Cr(VI)

“…Hematite (α-Fe 2 O 3 ) is one of the most promising photoelectric semiconductors because of its suitable bandgap (2.0–2.2 eV), stable phases, and abundance in nature. However, the applicability of hematite has been limited by its intrinsic properties, such as its low conductivity, short exited-state lifetime (< 10 ps), and short hole-diffusion length (2–4 nm) [ 7 – 9 ].…”