The renaissance of unsupported nanostructured catalysts for low-temperature fuel cells: from the size to the shape of metal nanostructures

A resurgence of interest in unsupported catalysts, commonly nanostructured Pt or Pt-based catalysts, for use in low-temperature fuel cells has occurred in recent years: indeed, the use of unsupported nanostructured catalysts may provide improved long-term stability during fuel cell operation compared to the carbon-supported catalysts because the carbon corrosion issue is eliminated. Catalyst utilization can be increased by developing novel nanostructures with high surface area and/or high catalytic activity. Indeed, in recent years, the strategy to increase the catalyst utilization has gone from decreasing the nanoparticle size to tailoring new nanostructures. This work presents an overview of recent studies on novel metal nanostructures for their possible use in low-temperature fuel cells, highlighting that these materials can better perform than the commonly utilized carbon-supported catalysts at similar catalyst loadings, having at the same time a higher stability.