SnO₂, IrO₂, Ta₂O₅, Bi₂O₃, and TiO₂ nanoparticle anodes: electrochemical oxidation coupled with the cathodic reduction of water to yield molecular H₂

In recent years, the search for environmentally friendly alternative energy sources with reduced carbon footprints has increased. The coupling of photovoltaic power sources with advanced electrolysis systems for hydrogen production via water splitting using organic contaminants as sacrificial electron donors has been considered to a be viable alternative. In this report, we demonstrated the feasibility of a scaled-up rooftop prototype of the proposed hybrid photovoltaic-electrolysis system, which utilizes semiconductor nanoparticles coated on to metal substrates as electrodes for the generation of hydrogen coupled with the oxidation of wastewater. Application of an anodic bias of >2.0 V to bismuth-doped TiO₂ (BiO _x –TiO₂) on Ti metal anodes with a sequential under-coatings of nanoparticulate SnO₂, IrO₂, Ta₂O₅, and Bi₂O₃ results in the electrochemical degradation of a variety of organic chemical contaminants in water (i.e., rhodamine B (Rh.B), methylene blue (MB), salicylic acid, triclosan, and phenol) and actual wastewater from a chemical manufacturing plant, while at the same time, molecular hydrogen is produced at stainless steel (SS) cathodes. The kinetics of the anodic substrates oxidation is investigated as a function of the cell current (I _cell), substrate concentration, and background electrolyte composition (e.g., NaCl, Na₂SO₄, or seawater). Average current efficiencies were found to be in the range of 4–22 %, while the cathodic current and energy efficiencies for hydrogen production were found to be in the range of 50–70 % and 20–40 %, respectively.