Enhancing oxygen reduction reaction activity and stability of platinum via oxide-carbon composites

A series of oxide-carbon composites using three different oxides (TiO ₂, SnO₂, ZnO) has been prepared using sol-gel (SG) and/or precipitation (P) chemical methods. A selective platinum deposition onto the oxide sites to obtain Pt/TiO₂-C, Pt/SnO₂-C and Pt/ZnO-C was carried out by generating electron-hole pairs on the oxide under UV-irradiation. This process takes advantage of the photogenerated electron on the oxide in the composite to reduce noble metal anions [PtCl₆] ^2- to Pt⁰ in the presence of a sacrificial electron donor. The Pt/oxide-carbon materials were characterized by XRD, TEM and CO stripping voltammetry combined with in situ infrared reflection absorption spectroscopy (FTIRS). The electrochemical stability of the different Pt/oxide-C catalysts was investigated by cyclic voltammetry in sulfuric acid medium and their electrochemical activity was evaluated in the oxygen reduction reaction (ORR) at RT. The Pt/oxide-carbon materials showed higher ORR activity than Pt/C catalyst. In situ FTIR spectroscopy coupled with CO stripping voltammetry reveals that CO oxidation on Pt/TiO₂-C and Pt/SnO₂-C samples takes place at lower electrode potentials as compared to Pt/C. Under the same conditions, the electrochemical stability of platinum center is higher on TiO₂-C and SnO₂-C composites than ZnO-C and C substrates.