The potential-dependent UV-Vis absorption spectra also demonstrates that the absorbance peak for Ti 3+ polaron formation is missing at potentials below U = -1.5 VSHE. This finding is corroborated with in situ electron paramagnetic resonance (EPR) spectroelectrochemical results in Figure , which provide direct evidence for the formation of a Ti 3+ polaron states (signal center at B = 355 mT). An EPR signal appears above U = -2.1 VSHE and increases as the electrode potential becomes more reductive.