Preparation of Nickel and Cobalt modified Ti-doped hematite photoanode for water splitting

• Main Author: Lim, Kenneth Zhao Wei
• Other Authors: Chen Zhong
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Materials
• Online Access: http://hdl.handle.net/10356/76753
• Institution: Nanyang Technological University

Photoelectrochemical water splitting has been widely investigated as a promising technology to efficiently generate hydrogen fuel through utlilising solar energy for the dissociation of water into its constituent components of hydrogen and oxygen gas. In the recent decades, hematite has been extensively studied as a potential material in photoanodes by exploiting its excellent properties such as good light absorption, non-toxcity, abundance and good photoelectrochemical stability. However, its inherent drawbacks of poor conductivity, a flat band potential Vfb too low in energy for water reduction, slow water oxidation kinetics and short miniority carrier diffusion length prevents it from achieving its maximum efficiency of 16%. To resolve these limitations, nanoscale modifications such as doping and surface treatments using co-catalyst loading or surface passivation were employed to improve the overall water splitting efficiency. In this project, Ti-doped hematite thin film photoanodes are fabricated by the means of hydrothermal synthesis and the photocurrent performance was recorded. Next, the hematite photoanode samples are further treated with cocatalysts under different hydrothermal conditions using precursor solutions containing Cobalt and Nickel ions mixed with organic linkers to deposit a layer of Co, Ni or Ni/Co based Metal Organic Frameworks (MOF). The final photocurrent performance was then recorded. An enhanced photocurrent density of 1.21 mA cm-2 at 0.4 V vs VAg/AgCl in 1 M NaOH electrolyte was recorded for the hematite photoanode sample surface-treated with a layer of Ni/Co-MOF under hydrothermal synthesis of 180min, as opposed to the value of 1.06 mA cm-2 in unmodified Ti-doped hematite photoanode sample. The photoanodes were subsequently characterised by X-ray Diffraction, Field Emission Scanning Electron Microscopy and Linear Sweep Voltammetry to examine the physical, crystallographic and electrochemical properties. Lastly, Electrochemical Impedance Spectroscopy is employed to confirm the electrical properties of the photoanodes.