The behavior of hydrothermally synthesized hematite nanorods prepared on spin coated seed layers

Abstract

Herein we report on the effect of varied spin-coated seed layer concentrations of Iron (III) chloride hexahydrate (FeCl3.6H2O) on the photoelectrochemical performance of hydrothermally synthesized hematite nanorods. The seed layers were prepared from 0.05, 0.07, 0.09, 0.11, and 0.13 M concentrations of FeCl3.6H2O. The nanorods were vertically aligned with slight inclinations over the seed layers with the two lowest molar concentrations (0.05 and 0.07 M) of FeCl3.6H2O. A further increase in seed layer concentrations transformed the nanorods as they grew over others and agglomerated into clusters. Structural analysis using X-ray diffraction (XRD) and Raman spectroscopy demonstrated uniform hematite crystalline peaks for all the samples. All samples absorbed highly in the visible region within an onset absorption edge wavelength ranging from 624 to 675 nm. Overall, the nanorods synthesized over the lowest seed layer concentration of 0.05 M of FeCl3.6H2O exhibited the highest photocurrent density of 0.077 mA/cm2 at 1.5 V vs. reversible hydrogen electrode. The results obtained provide important information about the structural, optical, and photoelectrochemical properties of hematite nanorods synthesized over varied seed layer concentrations. This is a key contribution in understanding and enhancing the hematite nanorods performance for photocatalytic applications.

Erbium and Titanium Co‐Doped Hematite Nanorods: Structural, Optical, and Catalytic Properties for Enhanced Water Splitting

“…This range is consistent with reported bandgap values for hematite NRs. [ 5,19 ] The bandgaps of all the Er/Ti‐doped NRs samples slightly increased by at least 1% compared to the 2.04 eV for the pristine hematite NRs, consistent with previous findings associated with sulfur (S) facile doped hematite. [ 48 ] This shift highlights the improvement in photon absorption by the Er and Er/Ti‐doped hematite NRs samples.…”

“…In addition, this correlated with the second‐highest film thickness exhibited by the pristine hematite NRs sample based on Beer–Lambert's law, which linearly relates film absorbance with film thickness. [ 5 ] The 40‐Er‐doped NRs sample also indicated strong absorption within the ≈370–420 nm range. This range is fitting and consistent with reported observations of enhanced absorption of hematite films within the visible spectrum (400–700 nm).…”

“…The clustering and coalescing of the NRs arrays of the as‐grown samples might have limited the effective surface area aspect for 40 ‐Er/30 ‐Ti, and 40 ‐Er/40 ‐Ti‐doped NRs, thus lowering the photon absorption. [ 5 ] In addition, the doped samples presented higher photon absorption with increasing crystallite size within the ≈350–450 nm range. Truffault et al [ 47 ] reported similar observations for hematite nanoparticles prepared for ultraviolet filtration.…”

“…[1,2] This presented room for investigations on the PEC water-splitting potential of semiconductors with smaller bandgaps, which are equally stable in aqueous environments. Many stable semiconductors with smaller bandgaps compared to TiO 2 , stable in aqueous media, and with smaller bandgaps that enhance visible light absorption like tungsten oxide (WO 3 ), [1] bismuth vanadate (BiVO 4 ), [1,3] and hematite, [4,5] have since been studied for PEC water splitting. Hematite has been extensively investigated due to its earth-abundance, small bandgap of %1.8-2.2 eV, [6] favorable valence band edge position for water oxidation, and stability in a wide pH range.…”

Facile Zn and Ni Co-Doped Hematite Nanorods for Efficient Photocatalytic Water Oxidation

“…However, the PEC performance of hematite is greatly hampered by the ultrafast charge recombination in its bulk and surface because of its short hole-diffusion path of 2–20 nm, poor electrical conductivity, and slow PEC kinetics for oxygen evolution, among others [ 11 ]. In a bid to enhance the performance of hematite electrodes, a range of strategies has been studied, such as using heterostructures [ 12 , 13 ], nanoscale engineering [ 14 ], seed layers [ 15 ], and elemental doping [ 16 ].…”