Preparo de nanoestruturas de AgPt ocas resistentes ao metanol em cátodos de células a combustível

Abstract

The maneuvering of catalysts at an atomic level is a versatile tool to control different properties, improving performance in applications of interest. Here, the main focus was to propose an energy device that could be used as a modifier of glassy carbon electrodes, with potential for use in alternative devices. Based on theoretical simulations, we found the best nanometric system to obtain an active system for the Oxygen Reduction Reaction (ORR) with a high tolerance to methanol (once the crossover effect - passage of methanol from one electrode to the other) happens routinely during the operation of Direct Methanol Fuel Cells (DMFCs). It was found that the interaction of oxygen is significantly more favorable in nanoshells of AgPt (empty materials), hampering the Methanol Oxidation Reaction (ROM) that can take place. This process was credited to the randomness of the arrangement of the atoms, lowering the possibility of three adjacent Pt sites. Nanoshells were prepared using a galvanic replacement approach and immobilized on silica, allowing remarkable stability after 1000 catalytic cycles. In addition, the high surface of the nanoshells promoted a high conductivity, even considering the immobilization of the material in silica. Notably, the system produced a 4-electron RRO mechanism with only 1.0 wt% Pt charge, and even with significantly lower kinetics when compared to the commercial Pt/C 20.0 wt% Pt, the system showed high tolerance to the crossover effect.