Vertically Oriented Iron Oxide Films Produced by Hydrothermal Process: Effect of Thermal Treatment on the Physical Chemical Properties

Abstract

Our study describes the influence of the thermal treatment on the fundamental properties of the vertical oriented iron oxide nanorods synthesized under hydrothermal condition onto a conductor substrate. X-ray diffraction and X-ray absorption near edge structure spectra were used to investigate the phase evolution from iron oxyhydroxide (β-FeOOH) to pure hematite phase. The formation of nanorods distributed along of substrate was observed by top-view SEM images and the rod growth preferentially oriented at the highly conductive (001) basal plane of hematite, perpendicular to the substrate. Light absorption capacity increases with the temperature of treatment and the electronic transitions (direct and indirect electronic transition) were estimated from this result. From the electrochemical measurement, the hematite/electrolyte interface was evaluated. These findings demonstrated that the temperature plays an important role on the hematite (structural, morphological, and catalytic) properties and that many influences must work in great harmony in order to produce a promising hematite photoanode.

From a Molecular 2Fe‐2Se Precursor to a Highly Efficient Iron Diselenide Electrocatalyst for Overall Water Splitting

“…Figure S24 (Supporting Information) shows the catalytic HER activity of FeSe 2 /NF and those of commercial IrO 2 /NF and Pt catalysts. A strong redox response was observed in the lower current density region for FeSe 2 /NF, indicating the reduction of Fe from mixed +2/+3 to a more reduced state akin to what is reported for FeO x ‐type materials . As a consequence of the interfering redox response in the region of lower current densities (−10 mA cm −2 ), the overpotentials were defined and compared at a current density of −100 mA cm −2 (Supporting Information, Table S10).…”

Hematite Surface Activation by Chemical Addition of Tin Oxide Layer

“…[23] In particular, herein, ag ood linear fit (R 2 > 0.99) of the Mott-Schottky plots for all pure and tin-modified hematite waso bserved ( Figure S5 in the Supporting Information). Accordingt oE quation (6), the slope of the plots was inverselyp roportional to the donor charge density of the semiconductor film. The positive slopes indicatet hat pure and tin-modified hematite electrodes are ntype semiconductors.…”

From a Molecular 2Fe‐2Se Precursor to a Highly Efficient Iron Diselenide Electrocatalyst for Overall Water Splitting

“…In the case of the OER by CV,the TEM and HRTEM images revealed athin amorphous shell, which appeared to start growing on the surface of the particles,c onfirming immediate changes on the surface at applied potentials (Supporting Information, Figure S27), while the thickness of the amorphous shell was further increased after OER by CP ( Supporting Information, Figure S28). [19] Both HRTEM and the SAED pattern showed that the core of the particle was intact (Supporting Information, Figure S28). [19] Both HRTEM and the SAED pattern showed that the core of the particle was intact (Supporting Information, Figure S28).…”

“…Theresulting overpotentials are not only one of the lowest in the series of chalcogenides,b ut also lower than that of most highperformance transition-metal-based catalysts (Supporting Information, Tables S7 and S8). [19] Scheme 1. [19] Scheme 1.…”