Core-Shell Nanoparticles and Three-Dimensional Nanostructured Materials as Electrocatalysts for Direct Alcohol Fuel Cells: How to Use Less Platinum and Not Die Trying

Abstract

Today, the major challenges that have to be overcome for a massive production and commercialization of direct alcohol fuel cell (DAFC) technologies for stationary, portable and transportation applications are the high cost and scarcity of noble metals, the deficient activity and selectivity of anode electrocatalysts and the long-term stability of the electrodes at temperatures compatible with available ionomeric membranes. In recent years, several strategies have been undertaken for improving the catalytic properties of Ptbased systems and for enhancing the noble metal utilization. A new approach to prepare highly active, selective and durable catalysts with low Pt loading comprises the production of multimetallic nanoparticles with a core-shell structure. Other promising strategy for the manufacture of nanostructured electrodes relies on the synthesis of three-dimensional materials to obtain thin-layered membrane-electrode assemblies (MEAs). The unsupported three-dimensional catalysts with core-shell structure provides high surface areas with low Pt loading, low contact resistance between current collector and electrode, facilitated mass transport of reactants and products and good longterm stability under operating conditions. Overall, the core-shell architecture makes possible the design of catalysts with several unique properties just by selecting the metals that form the shell and core. These elements can be chosen taking into account the segregation properties of the metals and their electronic and strain-inducing effects on the Pt shell. Studies have shown that the performance of core-shell systems is dependent on the crystalline structure and composition of the core and the lattice strain at the core-shell interface. According to the literature, the enhanced electrocatalytic properties of core-shell catalysts compared to conventional Pt-based materials can be explained in terms of the electronic modification of the shell by the core, lattice strain at the core-shell interface and improved Pt utilization.