Pollutant decomposition with simultaneous generation of hydrogen and electricity in a photogalvanic reactor

A small laboratory-scale reactor employing a nanocrystalline titanium dioxide anode and a platinum black cathode was evaluated for pollutant decomposition with simultaneous reduction of water to produce-hydrogen. The reactor requires only light as an energy input, and operates as a photogalvanic cell, producing electricity. Oxidative photodegradation of 4-chlorophenol, 2,4,5-trichlorophenol, and 4,4'-dichlorobiphenyl were achieved. Solutions of 0.1 mM chlorophenols were decomposed in 2 to 3 h, with an average turnover of 5.4 x 10(15) molecules/cm(-2) s(-1). Complete degradation of chlorophenols to carbon dioxide, water, and chloride ion was achieved in less than 6 h. Poorly water soluble 4,4'-dichlorobiphenyl adsorbed onto soil and suspended in a pH 13 anode solution was also decomposed: Hydrogen gas was produced at the cathode at a rate 1.4 ml h(-1) cm(-2) of electrode when using a pH 13 anode solution and a pH 1 cathode solution. The average reactor potential under these conditions was 1.53 V. Power output was 0.36 mW at a current density of 2 mA cm(-2).