Enhanced Solar Water Splitting by Swift Charge Separation in Au/FeOOH Sandwiched Single‐Crystalline Fe₂O₃ Nanoflake Photoelectrodes

Abstract

In this work, single crystalline α-Fe O nanoflakes (NFs) are formed in a highly dense array by Au seeding of a Fe substrate by a thermal oxidation technique. The NFs are conformally decorated with a thin FeOOH cocatalyst layer. Photoelectrochemical (PEC) measurements show that this photoanode, incorporating α-Fe O /FeOOH NFs rooted on the Au/Fe structure, exhibits significantly enhanced PEC water oxidation performance compared to the plain α-Fe O nanostructure on the Fe substrate. The α-Fe O /FeOOH NFs on Au/Fe photoanode yields a photocurrent density of 3.1 mA cm at 1.5 V , and a remarkably low onset potential of 0.5-0.6 V in 1 m KOH under AM 1.5G (100 mW cm ) simulated sunlight illumination. The enhancement in PEC performance can be attributed to a synergistic effect of the FeOOH top decoration and the Au underlayer, whereby FeOOH facilitates hole transfer at the interface of electrode/electrolyte and the Au layer provides a sink for the electron transport to the back contact. This results in a drastically improved charge-separation efficiency in the single crystalline α-Fe O NF photoanode.

Retracted: Dual Effects of Nanostructuring and Oxygen Vacancy on Photoelectrochemical Water Oxidation Activity of Superstructured and Defective Hematite Nanorods

“…For the Preparation of α‐Fe 2 O 3 NFs and NRs : For the preparation of the hematite NFs, iron foils (Alfa Aesar, 99.99%) were cleaned by sonication in ethanol for 10–20 min, followed by drying in an air stream. The iron foils were immersed in 5 × 10 −3 m HAuCl 4 (Sigma‐Aldrich, 99.9%) aqueous solution for 60–90 s by in situ precipitation of a nanoparticles on the Fe foils . The samples then were thermally annealed in a furnace (HF‐Keijing Furnace, KSL‐1100X) in air at 400 °C for 150 min.…”

“…The spectrum in Figure l shows that the upper layer (I) of the NFs consists mainly of α‐Fe 2 O 3 . The suboxide layer (II) can be assigned to Fe 3 O 4 on the basis of the Raman peaks at 633 cm −1 , which indicates that Fe 3 O 4 serves as the current contactor for electron transfer to the Fe substrate . Annealing treatment in Ar atmosphere creates 1D nanorods with a length of ≈1.5 µm and a diameter of ≈10 nm at the tip (Figure d,e).…”

“…Hematite NRs were prepared by a double‐step thermal oxidation/reduction method of iron foils ( Figure a). The α‐Fe 2 O 3 NFs were first prepared by thermal oxidation as previously reported, for which the Au nanoparticles layer was seeded on an Fe foil by self‐induced decoration. Next, the Fe layered with Au was thermally treated at 400 °C for 120–150 min, yielding the α‐Fe 2 O 3 NFs array of varying diameters and lengths.…”

A BiOCl/β-FeOOH heterojunction for HER photocatalytic performance under visible-light illumination

“…To further study the chemical state of the surface element, the corresponding core‐level spectra were supplied. Especially, the Fe 2p core‐level spectrum of BFOH‐2 is very different from that of Fe 3 O 4 , and the peaks at 725.1 eV and 711.3 eV are attributed to the Fe 2p 1/2 and Fe 2p 3/2 of Fe 3+ in β‐FeOOH (Figure B), and the peaks at 532.8 eV, 530.7 eV, and 527.9 eV (Figure C) are attributed to the O 1 s in BiOCl (532.8 eV and 527.9 eV) and β‐FeOOH (530.7 eV) . Furthermore, The core‐level spectra of Bi and Cl elements were shown in Figure S2.…”

Ternary WO3/Porous‐BiVO4/FeOOH Hierarchical Architectures: Towards Highly Efficient Photoelectrochemical Performance

“…Since the first report on titanium dioxide (TiO 2 ) electrodes for PEC water splitting in 1972, considerable efforts have been made in the past decades to achieve a satisfied solar‐to‐hydrogen conversion efficiency . Especially, some typical semiconductors have been explored for use in solar PEC water splitting, such as TiO 2 , ZnO, Fe 2 O 3 , WO 3 and BiVO 4 …”