Ti/Pt-Pd-Based Nanocomposite: Effects of Metal Oxides on the Oxygen Reduction Reaction

Over the last few years, there has been an intensive search for stable and highly active electrocatalysts, which are intended to be applied in oxygen reduction reaction (ORR) preferably without the use of noble metals or with the application of a very small quantity of these metals in the process. Electrocatalysts that satisfy these conditions can be composed of Ti and other metals, supported or not by carbonaceous materials. The present work reports the application of synthesized three-dimensional Ti/Pt-Pd nanoparticles with highly rough surfaces supported on graphene nanoribbons (Ti/Pt-Pd/GNR nanocomposite) by a single one-pot reaction, and applied in ORR. Unlike the effect of strong metal-support interaction (SMSI), which favors electrons transfer from the metal support to the catalyst, the mechanism employed in this study favored the transfer of electrons from the catalyst to the metal support; in other words, the mechanism led to the oxidation of Pt and Pd. Pt, which exhibited Pt-Pd type alloy features, was found to be more externally distributed at the rough surface of the metallic structures. Additionally, Ti, which presented oxide features, was found to be even more externally distributed at the surface of Pt-Pd on non-electrochemically and electrochemically stabilized Ti/Pt-Pd/GNR nanocomposite electrodes. Since all these metals have great amounts of different oxides (i. e. are highly oxidized), the oxides are found to be energetically responsible for the improvement in ORR electrocatalytic activity and stability of Ti/Pt-Pd/GNR/GC electrodes in comparison with the ORR responses for PtC TKK/GC and Pt-Pd/GNR/GC modified electrodes. To Ti-containing catalysts, the high activity is attributable to enhancing the intrinsic activity and the high selectivity to 4-electron ORR is due to the fact that presence of Ti contributes to oxygen-binding energy of these nanocomposites shifts toward more positive values (weakening oxygen bonding).