Iron Oxide Films Prepared by Rapid Thermal Processing for Solar Energy Conversion

Abstract

Hematite is a promising and extensively investigated material for various photoelectrochemical (PEC) processes for energy conversion and storage, in particular for oxidation reactions. Thermal treatments during synthesis of hematite are found to affect the performance of hematite electrodes considerably. Herein, we present hematite thin films fabricated via one-step oxidation of Fe by rapid thermal processing (RTP). In particular, we investigate the effect of oxidation temperature on the PEC properties of hematite. Films prepared at 750 °C show the highest activity towards water oxidation. These films show the largest average grain size and the highest charge carrier density, as determined from electron microscopy and impedance spectroscopy analysis. We believe that the fast processing enabled by RTP makes this technique a preferred method for investigation of novel materials and architectures, potentially also on nanostructured electrodes, where retaining high surface area is crucial to maximize performance.

Elevated temperature transmission Kikuchi diffraction in the SEM

“…Since transmission Kikuchi diffraction (TKD) was introduced by Keller and Geiss [1,2] in 2012, the technique has received increasing interest and has been applied to investigate several material systems [3][4][5][6][7][8][9][10][11] within a large range of fields [1,[4][5][6][7][8]10,[12][13][14]. Additionally, a considerable focus has been directed to further understanding and optimising the technique [9,11,[14][15][16][17][18][19][20]; besides improvements related to the acquisition software, and some new hardware developments [21][22][23].…”

Formation of iron oxide nanoparticles for the photooxidation of water: Alteration of finite size effects from ferrihydrite to hematite

“…A highly investigated research field is the photoelectrolysis of water with hematite due to the global demand for hydrogen with dwindling fossil energy sources. Hematite represents a low-cost photocatalyst for water oxidation as it is the most common iron ore and a semiconductor with a bandgap around 1.9–2.2 eV 16 – 30 . By the generation of oxygen under light irradiation it can compete with other common photocatalyst systems such as titania 18 .…”

Electrochemistry of Sputtered Hematite Photoanodes: A Comparison of Metallic DC versus Reactive RF Sputtering

“…The photocurrent of the DC film achieved herein is comparable to other bare, unmodified hematite thin films of 40–50 nm thickness prepared by various methods, such as sputtering or ALD. 16,18,27 However, it is lower than the hematite layer deposited by Jia et al by RF sputtering from a ceramic hematite target (1.3 mA cm –2 at 1.5 V versus RHE). 15 The higher performance of the hematite films deposited by Jia et al is most probably related to less physical defects in the bulk of the film.…”