Electrodeposited Aluminum-Doped α-Fe₂O₃ Photoelectrodes: Experiment and Theory

Abstract

Substitutional doping can improve the electronic properties of R-Fe 2 O 3 for the solar photoelectrochemical (PEC) applications. Generally speaking, nonisovalent substitutional doping helps to enhance the electronic conductivity of R-Fe 2 O 3 . However, we found that the introduction of strain in the lattice, which is achieved by isovalent substitutional doping of an Al, can also improve the electronic properties. R-Fe 2 O 3 films with the Al dopant atomic concentration varying from 0 to 10% were prepared by electrodeposition, and their performance for photoelectrochemical hydrogen production was characterized. Results indicate that the incident photon conversion efficiency (IPCE) for ∼0.45 at-% Al substitution increases by 2-to 3-fold over undoped samples. Density-functional theory (DFT) was utilized to interpret the experimental findings. It was shown that although no substantial change to the electronic structure, a contraction of the crystal lattice due to the isovalent replacement of Fe 3þ by an Al 3þ benefits the small polaron migration, resulting in an improvement in conductivity compared to the undoped samples.

Magnetic field cycling effect on the non-linear current-voltage characteristics and magnetic field induced negative differential resistance in α-Fe1.64Ga0.36O3 oxide

“…Electrically, hematite is a charge-transfer type semiconductor with band gap ∼ 2.2 eV and non-suitable for spintronics applications due to its low electrical conductivity. 8 Recent reports 3,4,8,9 predicted enhancement of electrical conductivity in metal doped hematite. There is not much progress to understand either the mechanism of enhanced conductivity or the hidden magneto-transport properties in metal doped hematite.…”

Activation of Hematite Nanorod Arrays for Photoelectrochemical Water Splitting

“…The surface features in these images are similar to leading reports of hematite produced by solution grown material after high temperature annealing. [19,25] Despite the improvements, the J OER values remain considerably short of the current standard of 2.4 mA/cm 2 achieved by APCVD without a catalyst.…”

“…Most leading hematite electrodes are highly doped compounds, and numerous elements (Si, Ti, Pt, Cr, Mo, Al) have been shown to be beneficial. [11,17,18,[23][24][25]33] High levels of doping reduce the Debye length in hematite to below 1 nm, which has been suggested to improve charge transport and separation. [24] To further investigate the role of doping a Mott-Schottky analysis was performed at 500 Hz (Fig.…”

“…First, all of the films displayed a flat band potential of ~0.4 V vs RHE regardless of the annealing condition, which is consistent with literature reports for hematite thin films. [24,25] Somewhat surprising is that the slope in the linear region was largely unaffected by the choice of annealing conditions, varying by no more than a factor of 3.…”

Enhanced Water Splitting on Thin-film Hematite Photoanodes Functionalized with Lithographically Fabricated Au Nanoparticles

“…The 25-nm Fe 2 O 3 samples show not only the highest relative increase in photocurrent (of roughly a factor of six), but also the highest photocurrent in absolute terms. A beneficial effect of nanostructures of various metals (Au, [17] Ti [26] and even Zn [27] ) on the onset potential for the photocurrent has been reported previously. Catalytic activity of the metal has then been accounted for such influence.…”