Photoelectrocatalytic Hydrogen Production Using a TiO2/WO3 Bilayer Photocatalyst in the Presence of Ethanol as a Fuel

Abstract

Photoelectrocatalytic hydrogen production was studied by using a photoelectrochemical cell where the photoanode was made by depositing on FTO electrodes either a nanoparticulate WO3 film alone or a bilayer film made of nanoparticulate WO3 at the bottom covered with a nanoparticulate TiO2 film on the top. Both the electric current and the hydrogen produced by the photoelectrocatalysis cell substantially increased by adding the top titania layer. The presence of this layer did not affect the current-voltage characteristics of the cell (besides the increase of the current density). This was an indication that the flow of electrons in the combined semiconductor photoanode was through the WO3 layer. The increase of the current was mainly attributed to the passivation of the surface recombination sites on WO3 contributing to the limitation of charge recombination mechanisms. In addition, the top titania layer may have contributed to photon absorption by back scattering of light and thus by enhancement of light absorption by WO3. Relatively high charge densities were recorded, owing both to the improvement of the photoanode by the combined photocatalyst and to the presence of ethanol as the sacrificial agent (fuel), which affected the recorded current by “current doubling” phenomena. Hydrogen was produced under electric bias using a simple cathode electrode made of carbon paper carrying carbon black as the electrocatalyst. This electrode gave a Faradaic efficiency of 58% for hydrogen production.

Anionic Exchange Membrane for Photo-Electrolysis Application

“…Energy produced by the sun in one hour is equal to the amount necessary for the world’s human population in one year [ 10 ]. Thus, storing energy through the production of solar fuel (hydrogen by water-splitting or hydrocarbons by carbon dioxide reduction) and generating energy from them, when it is necessary, has become a “green” challenge [ 11 , 12 , 13 , 14 ].…”

Heterojunction of WO3 Particle and g‐C3N4 Nanowire for Enhanced Photocatalytic Hydrogen Evolution

“…The band gap of the WO 3 /g‐C 3 N 4 composite is slightly smaller than that of the pure CN. The Mott‐Schottky curves are shown in Figure 5(b), and the slope of the fitted curve is positive, which proves that the photocatalyst is an n‐type semiconductor [48–50] . The flat band potentials are −0.16 V and −0.43 V (vs. Ag/AgCl) of pure CN and 0.10WO 3 /CN, respectively.…”

“…The Mott-Schottky curves are shown in Figure 5(b), and the slope of the fitted curve is positive, which proves that the photocatalyst is an n-type semiconductor. [48][49][50] The flat band potentials are À 0.16 V and À 0.43 V (vs. Ag/AgCl) of pure CN and 0.10WO 3 /CN, respectively. Compared with pure CN, the flat band potential of 0.10WO 3 /CN is more negative.…”

Photoelectrocatalytic Hydrogen Peroxide Production Using Nanoparticulate WO3 as Photocatalyst and Glycerol or Ethanol as Sacrificial Agents

“…Some leaching of WO3 from FTO electrodes was detected, whereas some salt deposit on carbon cloth electrodes could also be detected. It is possible that combination of WO3 with other oxide semiconductors might improve photoanode stability [25,26], but this is a matter of future work. Reproduction of the above data requires fresh electrodes and electrolytes.…”