The computational and experimental results in Figures and clearly show that the TiO2 (101) can store a high amount of negative charge by reducing Ti 4+ to Ti 3+ polarons when the electrode potential is sufficiently reducing. The polarons are formed and observed exclusively at the top layer of TiO2 (101) surface, which is expected to enhance surface conductivity. The formation of surface polarons is in line with in situ microcell-based electronic/electrochemical and STM 67 experiments demonstrating that charge carriers localize and conduct charge at the semiconductor surfaces rather than in the bulk under negative electrode potential conditions.