Designing Photoelectrodes for Photocatalytic Fuel Cells and Elucidating the Effects of Organic Substrates

Abstract

Photocatalytic fuel cells (PFCs) are constructed from anodized photoanodes with the aim of effectively converting organic materials into solar electricity. The syntheses of the photoanodes (TiO2 , WO3 , and Nb2 O5 ) were optimized using the statistical 2(k) factorial design. A systematic study was carried out to catalog the influence of eleven types of organic substrate on the photocurrent responses of the photoanodes, showing dependence on the adsorption of the organic substrates and on the associated photocatalytic degradation mechanisms. Strong adsorbates, such as carboxylic acids, generated high photocurrent enhancements. Simple and short-chained molecules, such as formic acid and methanol, are the most efficient in the corresponding carboxylic acid and alcohol groups as a result of their fast degradation kinetics. The TiO2 -based PFC yielded the highest photocurrent and obtainable power, whereas the Nb2 O5 -based PFC achieved the highest open-circuit voltage, which is consistent with its most negative Fermi level.

Gas phase photofuel cell consisting of WO3- and TiO2-photoanodes and an air-exposed cathode for simultaneous air purification and electricity generation

“…The fill factor (FF) was calculated for all photocatalysts by dividing Pmax by the theoretical maximal power output (Voc.Jsc). The FFs obtained with both TiO2 and WO3-based photocatalysts are significantly higher than those obtained in liquid phase PFC systems working with a methanol solution as reported by Hu and co-workers, showing FFs of 0.17 and 0.11 for TiO2 and WO3, respectively [41], while FFs up to 0.39 are attained in our work. This can be attributed to the cell configuration used in this study combining anode, electrolyte and cathode in a MEA, reducing electrolyte resistance and associated current losses due to the reduced distance between the two electrodes.…”

“…This can be attributed to the cell configuration used in this study combining anode, electrolyte and cathode in a MEA, reducing electrolyte resistance and associated current losses due to the reduced distance between the two electrodes. In the study of Hu and coworkers the TiO2-photoanode performed better than the WO3 one [41]. Both the difference in cell configuration (reduced recombination and thus possibly benefiting WO3), operating phase (drastically lower diffusion limitations could play an important role in gas phase operation, amongst others) and the different nature of the studied photocatalysts can contribute to this difference.…”

Visible-Light-Driven Photocatalytic Fuel Cell with an Ag-TiO2 Carbon Foam Anode for Simultaneous 4-Chlorophenol Degradation and Energy Recovery

“…Figure 3a shows that the degradation efficiency after 6 h when using sodium sulfate as the electrolyte was higher than when using the other electrolytes. This indicated that the presence of SO [37]. Although •OH played a supporting role in the PFC, the consumption of •OH adversely affected 4-CP degradation, even more than the presence of SO 4 2− .…”

“…The hydrolysis of HCO3 − and ionization of H2PO4 − exerted a significant influence on H2O2, by reducing the amount of H2O2 and weakening its oxidation ability, respectively. Cl − could be oxidized to ClO• − by •OH [37]. Although •OH played a supporting role in the PFC, the consumption of •OH adversely affected 4-CP degradation, even more than the presence of SO4 2− .…”

Photocatalytic fuel cell – A review

“…Based on the location of O 2p orbital, the VB positions of binary metal oxides are more positive than that of oxidation positions, leading to wide energy bandgaps. [70] Strong solar PFC effect could also be obtained by making the photoanode with other visible-light absorption semiconductor materials, such as WO3/W, [71][72][73][74] ZnO/Zn, [75] Nb2O5 [72] and BiOCl. [76] However, the performance of PFC consisting of CdS/WO3 composite electrode exhibits poor stability due to photocorrosion, poor photoexcited charge separation and unfavorable band structure.…”