1908
Study of the Water Splitting Performance of Hematite Thin Films Prepared By DC and Reactive RF Sputtering

Thursday, 17 May 2018: 10:45
Room 612 (Washington State Convention Center)
R. Sinha (Dutch Institute for Fundamental Energy Research), R. Lavrijsen (Eindhoven University of Technology (TU/e)), M. C. M. van de Sanden (Dutch Institute for Fundamental Energy Research, Eindhoven University of Technology (TU/e)), and A. Bieberle-Hütter (Dutch Institute for Fundamental Energy Research)
Metal oxides such as Fe2O3, WO3 or BiVO4 have been extensively studied as suitable materials for photoelectrochemical (PEC) water splitting [1]. However, the water splitting performance of these materials is limited by short charge carrier lifetime, high charge carrier recombination effects and slow water oxidation kinetics [2]. These material drawbacks lead to a high sensitivity of the water splitting efficiency on the synthesis technique utilised to fabricate the metal oxide films.

In this work, hematite thin films are utilised as a model system to understand the effect of variation in the synthesis process on the water splitting performance [3]. Thin films of 40-50 nm thickness are prepared by DC and reactive RF sputtering, followed by annealing at 800°C. It is observed that the DC sputtered films exhibit higher PEC performance with 40 times higher photocurrent at 1.23 V (versus RHE) and 300 mV lower onset potential, as shown in figure 1(a).

From electrochemical impedance spectroscopy (EIS) measurements we find that the DC sputtered thin films exhibit faster charge transfer kinetics as shown by the higher charge transfer rate constant for the oxygen evolution reaction (figure 1(b)). Intensity modulated photocurrent spectroscopy (IMPS) and hole scavenger measurements show that DC sputtered films also have lower surface and bulk recombination effects, respectively, as compared to the reactive RF sputtered films. The variation in the PEC properties is related to the large differences observed in the morphology, surface chemistry and optical properties of the DC and RF sputtered thin films as studied by techniques such as cross-sectional TEM, SEM, XPS and UV-Vis spectroscopy.

References

[1] M.G. Walter, E.L. Warren, J.R. McKone, S.W. Boettcher, Q. Mi, E.A. Santori, N.S. Lewis, Chemical Reviews, 110 (2010) 6446-6473.

[2] K. Rajeshwar, A. Thomas, C. Janáky, Photocatalytic Activity of Inorganic Semiconductor Surfaces: Myths, Hype, and Reality, The Journal of Physical Chemistry Letters, 6 (2015) 139-147

[3] R. Sinha, R. Lavrijsen, M. C. M. van de Sanden, A. Bieberle-Hütter, In Preparation