Energy-Band Structure as Basis for Semiconductor n-Bi₂S₃/n-Bi₂O₃ Photocatalyst Design

By employing model semiconductor composite system n-type Bi 2 S 3 /n-type Bi 2 O 3 , and the concept of semiconductor electrochemistry, basic principles for the design of (photo)catalyst materials with application in energy conversion and advanced wastewater treatment processes, were analyzed and discussed. Absolute energy values of conduction band edge, E CB , and valence band edge, E VB , were correlated with the semiconductor's stability against decomposition and competitive redox reactions of free radical species formation. The energy-band diagrams were constructed for the proposed photocatalytic system. The E CB position was determined from the flatband potential, E FB , derived from Mott-Schottky analysis taking into account an additional potential drop in the Helmholtz layer due to the adsorption of potential determining ions on the semiconductor surface. Special attention was given to the accuracy of E FB calculation due to the frequency dispersion of the capacitance.