Carbon-mediated photoinduced reactions as a key factor in the photocatalytic performance of C/TiO2

Abstract

We have explored the photoelectrochemical behavior of carbon/titania composites, aiming at understanding the mechanisms of the photoinduced processes occurring in such hybrid photocatalysts that lead to enhanced photocatalytic efficiencies of the pristine semiconductor for the photodegradation of refractory pollutants in water. In a first step, spectrometric techniques have been applied to investigate the structural and optical properties of the carbon/semiconductor composites compared to the intrinsic characteristics of the unsupported semiconductor. The second approach consisted of the preparation of thin-film electrodes to explore the photoinduced reactions occurring at the interface under UV light and bias potential. The gathered results provided experimental evidence on the carbon-mediated photoinduced reactions, distinguishing different mechanisms: (i) the carbon matrix acts as a charge-trapping network that modifies the fate of the photogenerated charge carriers (avoiding recombination and thus enhancing the photocatalytic efficiency); (ii) illumination of the carbon additive renders photogenerated carriers due to π–π* transitions, capable of participating in charge transfer reactions with electron donors present in the reaction medium. Our results point out that beyond the beneficial effect of the porosity of the support, the carbon matrix does play an important role in the photoinduced reactions of carbon-supported photocatalysts.