5TH International Congress on Technology - Engineering & Science - Kuala Lumpur - Malaysia (2018-02-01)

Cobalt Phosphate Oxygen Evolution Catalyst For Efficient Photoelectrochemical Water Splitting

Development of novel energetic scenario utilizing two renewable resources sunlight and water would be sufficient to solve the energy crisis the world is currently facing. In this perspective, natural photosynthesis is a great inspiration for the scientific community by storing the solar energy in a fuel via rearranging the comical bonds of water (1). As the oxygen evolving center of photosystem II in plant cell, a similar simple and effective earth-abundant catalyst was discovered as oxygen evolution catalysts by Nocera and coworkers (2, 3). In this study, the synthesis and photoelectrochemical characterization of cobalt phosphate oxygen evolution catalyst (Co-Pi OEC) modified photoanode and heterojunction photoanode comprising one dimentional nanostructure WO3, and WO3 covered with BiVO4 was investigated. The 1-D nanostructure WO3 was prepared by flame vapor deposition (FVD) and covered by BiVO4 using spin coating method. The Co-Pi OEC particles were deposited onto the above mentioned WO3 photoanode and core-shell WO3/BiVO4 heterojunction structure by photo-assisted electrodeposition method respectively. The performance of Co-Pi OEC modified WO3 photoanode and WO3/BiVO4 was studied comparing to the unmodified one repectively. When Co-Pi photo-assisted electrodeposited on WO3, photocurrent increased while increasing the deposition time until 100s under the AM 1.5 one sun under 0.6VSCE deposition potential. After 150s deposition time, photocurrent density abruptly decreased below the intial photocurent of bare WO3. When Co-Pi photo-assisted electrodeposited on WO3/BiVO4, photocurrent density consistenly enhanced obviously at lower potential with the deposition time of 150s under AM 1.5 one sun. Chronoamperometry measurement before and after deposition of Co-Pi on WO3/BiVO4 shows that photocurrent enhancement observed with Co-Pi OEC modifiction is more profound at lower potential and it is probably due to its catalytic ability towards water oxidation (4). Basically, as there may exist some surafce states at the surface of Co-Pi modified photoanode materials at the low potential, photogenerated holes and electrons can be recombined at surface easily, which is the competitive process of the oxygen evolution reaction (5). At higher potential, the possibility of recombination is reduced due to large band bending. However, under Co-Pi modification, it may passivate the surface states or provide pathway for accumulated holes on the surface, thus, suppressing recombination reaction at the interface.
Tangnuer Sadike, Jin-Rui Ding, Kyo-Seon Kim