Single atomic Pt supported on TiC was prepared from chloride Pt precursors, then the chloride ligands were intentionally removed by increasing the reduction temperature. The 0.2 wt% Pt/TiC catalyst reduced at 300 °C had more reduced Pt single-atoms with fewer chloride ligands and exhibited the highest currents for H2O2 formation in the electrochemical oxygen reduction reaction. Controlling the oxidation state of the single-atoms is very important to maximize the activity of the single-atom catalysts.