Waste-to-Energy Conversion for Sustainability: Production of Hydrogen and Elimination of Chemical Wastes in Water with Solar Light

A Bi-doped TiO2 anode, which is prepared from a mixed metal oxide coating deposited on Ti metal, is shown to be efficient for conventional water splitting. In this hybrid photovoltaic – electrochemical system, a photovoltaic (PV) cell is used to convert solar light to electricity which is then used to oxidize a series of phenolic compounds at the semiconductor anode to carbon dioxide with the simultaneous production of molecular hydrogen from water/proton reduction at the stainless steel cathode. Degradation of phenol in the presence of a background NaCl electrolyte produces chlorinated phenols as reaction intermediates which are subsequently oxidized completely to carbon dioxide and low-molecular weight carboxylic acids. The anodic current efficiency for the complete oxidation of phenolic compounds ranges from 3 to 17%, while the cathodic current efficiency and the energy efficiency for hydrogen gas generation range from 68 to 95% and from 30 to 70%, respectively.