Photoelectrochemistry of solution processed hematite nanoparticles, nanoparticle-chains and nanorods

Abstract

We report a coordination chemistry approach for shape-controlled synthesis of a-Fe 2 O 3 (hematite) nanostructures. Three distinct morphologies viz. nanoparticles, nanoparticle-chains and nanorods were synthesized from inorganic iron precursor sources of nitrate, sulfate and chloride, respectively, in the presence of urea as a pH regulating agent and were characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy. The responsible growth mechanism and possible factors controlling the morphologies are explored. Photoelectrochemical cells constructed by utilizing these nanostructures produced stable photocurrents in iodide electrolyte. The nanoparticle-chains morphology of a-Fe 2 O 3 revealed the highest photocurrent density of 0.36 mA cm 22 at 0 V bias conditions under 1 Sun illumination. The reason for the high performance is investigated with the help of impedance spectroscopy analysis, wherein the electrode composed of nanoparticle-chains affords the lowest charge transfer resistance and thereby the highest photoconversion yield, as compared to those of the nanoparticle and nanorod electrodes.

Tuning α-Fe2O3 nanotube arrays for the oxygen reduction reaction in alkaline media

“…Recently, several attempts have been encountered in the literature for the preparation of a-Fe 2 O 3 nanoparticles, nanorods, nanowires, and nanotubes. 24,25 The aligned nanotube can achieve higher electron mobility by decreasing electron-hole recombination and obtain a larger surface area without an increase in geometric area, which could be expected to achieve higher ORR activities. 26 Among the various fabrication methods, the electrochemical anodization method shows the advantages of easily controllable pore size, good uniformity, and conformability over large areas at a low cost.…”

Hedgehog-like hierarchical ZnO needle-clusters with superior electron transfer kinetics for dye-sensitized solar cells

“…[24][25][26][27][28] Simultaneously, much of the current research focuses on using a series of other wide-band-gap semiconductor materials as potential alternatives to TiO 2 . [29][30][31][32] Among these metal oxides, ZnO has been considered a prime photoelectrode material candidate due to its similar electronic band (3.37 eV) structure to TiO 2 , higher electron mobility (10 2 cm 2 V À1 s À1 ) and comparable electron injection efficiency. 33,34 In addition, ZnO exhibits a diverse range of morphologies due to the ease of crystallization and controllable anisotropic growth compared with TiO 2 .…”

Asymmetric Reduction of Gold Nanoparticles into Thermoplasmonic Polydimethylsiloxane Thin Films

“…The rates of nucleation and growth of metallic nanoparticles formed via photoreduction were shown to be strongly affected by initial metal concentration . Shape-controlled synthesis of hematite (iron) nanostructures was achieved by controlling the local iron ion availability for reaction with the use of different ligands, resulting in particles, rods, and chain structures similar to the networks seen here . Increasing the ratio of reducing agent concentration relative to TCA concentration was shown to increase average particle size in the prior work utilizing diffusion of TCA into PDMS .…”

“…30 Shapecontrolled synthesis of hematite (iron) nanostructures was achieved by controlling the local iron ion availability for reaction with the use of different ligands, resulting in particles, rods, and chain structures similar to the networks seen here. 31 Increasing the ratio of reducing agent concentration relative to TCA concentration was shown to increase average particle size in the prior work utilizing diffusion of TCA into PDMS. 23 Exposure time was seen to have a strong effect on particle size in these prior investigations, but time was kept constant for all the samples in this work.…”