Photoelectrochemical and photocatalytic investigation of the oxidative formation of H2 from a borane-ammonia complex using an organic p-n bilayer comprising a p-type cobalt phthalocyanine and an n-type perylene derivative

An organic p-n bilayer photocatalyst, comprising a perylene derivative (PTCBI, n-type) and cobalt phthalocyanine (CoPc, n-type), is utilized for the oxidative formation of molecular hydrogen (H2) from a borane-ammonia complex (NH3BH3, AB). The formation of H2 occurs photocatalytically at the surface of CoPc in the organo-bilayer, along with the reduction of O2 by a reducing power generated at PTCBI. The mechanism to illustrate the H2-formation from AB by the organo-photocatalyst may be different from that of the conventional photocatalysis by inorganic semiconductors. To further understand the mechanism of H2-formation, photoelectrochemistry is further investigated using the PTCBI/CoPc bilayer as a photoanode. Considering the resulting faradaic efficiency for H2-formation, at least two possible equations have to be suggested: BH3OH− (intermediate) + 3OH− → BO2− + 3/2H2 + 2H2O + 3e− and BH3OH− (intermediate) + 2OH− → BO2− + 2H2 + H2O + 2e−.