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{prime}-dichlorobiphenyl were achieved. Solutions of 0.1 mM chlorophenols were decomposed in 2 to 3 h, with an average turnover of 5.4 {times} 10{sup 15} molecules/cm{sup {minus}2} s{sup {minus}1}. Complete degradation of chlorophenols to carbon dioxide, water, and chloride ion was achieved in less than 6 h. Poorly water soluble 4,4{prime}-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 cm{sup 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{sup 2}.