Solar-Driven Photoreactor for Water Remediation Based on n-Type TiO₂ and p-Type Ag/AgBiW₂O₈/Bi₂WO₆ Light-Responsive Air-Fed Gas Diffusion Electrodes

Abstract

Photocathodes with multiphasic Ag/AgBiW2O8/Bi2WO6 (Ag/ABW/BW) particles, obtained by hydrothermal synthesis, were evaluated for light-assisted oxygen reduction reaction (ORR). Under irradiation, electrodes of Ag/ABW/BW deposited on FTO exhibited ORR cathodic photocurrent enhancement and impedance decreasing (p-type semiconducting behavior). The Ag/ABW/BW particles were deposited on graphite sintered with PTFE; under irradiation and flow of compressed air, this gas diffusion electrode (GDE) produced H2O2 from ORR. The air-fed GDE|Ag/ABW/BW photocathode was associated with an FTO|TiO2 photoanode and externally connected with a silicon solar cell. Irradiated by a solar simulator, this photoreactor was used for remediation of amoxicillin (AMX) aqueous solution. After 3 h, 53% of AMX was degraded, while with a bare GDE, the AMX removal was 30%. Smaller values (<15%) were obtained using Pt or a GDE|Ag/ABW/BW under N2 flow as the cathode, since these configurations preclude the H2O2 production from ORR. Thus, association of photoactive electrodes in this innovative solar-driven photoreactor provides a sustainable system for water remediation.

Strategies for the synthesis of complex oxides for application as light-responsive electrodes in photoelectrochemical cells – a review

“…Photocathodes require p-type semiconductors, which are rarer and more difficult to obtain from lowcost and abundant materials than n-type semiconductors. Some Ag and Cu based compounds can act as p-type semiconductors; 12,130 moreover Cu-based materials have been attracting more interest, particularly for the CO 2 reduction reaction (CO 2 RR), since copper compounds generally favour the conversion of CO 2 into C 2 and C 3 products, such as ethanol and propanol. 131 However, Cu oxides, especially as binary materials, tend to suffer from rapid photocorrosion in irradiated aqueous solution, which is attributed to the Cu 2 O/Cu reduction potential value, placed within the semiconductor band gap.…”

“…Photocathodes require p-type semiconductors, which are rarer and more difficult to obtain from low-cost and abundant materials than n-type semiconductors. Some Ag and Cu based compounds can act as p-type semiconductors; 12,130 moreover Cu-based materials have been attracting more interest, particularly for the CO 2 reduction reaction (CO 2 RR), since copper compounds generally favour the conversion of CO 2 into C 2 and C 3 products, such as ethanol and propanol. 131…”