Conduction band energy determination by variable temperature spectroelectrochemistry

The conduction and valence band energy positions of nanostructured semiconductors are arguably the most important physical parameters of these materials; however they have also proven the most problematic to measure. In this work, we describe a new method of variable temperature spectroelectrochemistry, which is a simple way to directly measure the absolute conduction band energy of nanostructured electrodes with minimal assumptions. In addition, the extinction coefficient of free conduction band electrons is simultaneously determined by this method. Results of variable temperature spectroelectrochemistry measurements of nanoparticle TiO₂ electrodes are presented. Values of −0.761 to −0.936 V vs. Ag/AgCl were determined for the conduction band energy, which was found to shift with E_F in excellent agreement with literature estimates. We believe this method will be applicable to a large variety of materials and systems.