(Table ). The results also show that the accumulation of negative surface charge (Ti 3+ polarons) is driven by the applied electrode potential and that VO shifts the polaron formation potentials to significantly more oxidizing potentials compared to pristine TiO2. Furthermore, the charge and spin analyses confirm that the bi-Ti 3+ is localized next to VO at PZC of 0.5 VSHE. as seen by the non-zero AMMs of two Ti atoms (Ti5c and Ti4c) neighboring the vacancy (Figure ) and occupied Ti-3d states (see Figure ). At U = 1.5 VSHE, the surface carries a positive charge of 0.66e -(Figure ), with only one Ti 3+ as evidenced by the AMM values shown in Figure . The PDOS plot (Figure ) of the Ti atom demonstrates that one Ti 3+ in bi-Ti 3+ has partially unoccupied Ti-3d states, reinforcing the interpretation that a single-polaron state is present at U = 1.5 VSHE. Decreasing the electrode potential to -1.0 VSHE leads to the accumulation of an additional electron and the formation of a second or even a third Ti 3+ polaron with AMM of 1.0 μB (see Figure and).