Toward Platinum Group Metal-Free Catalysts for Hydrogen/Air Proton-Exchange Membrane Fuel Cells: Catalyst activity in platinum-free substitute cathode and anode materials

The status, concepts and challenges toward catalysts free of platinum group metal (pgm) elements for proton-exchange membrane fuel cells (PEMFC) are reviewed. Due to the limited reserves of noble metals in the Earth’s crust, a major challenge for the worldwide development of PEMFC technology is to replace Pt with pgm-free catalysts with sufficient activity and stability. The priority target is the substitution of cathode catalysts (oxygen reduction) that account for more than 80% of pgms in current PEMFCs. Regarding hydrogen oxidation at the anode, ultralow Pt content electrodes have demonstrated good performance, but alternative non-pgm anode catalysts are desirable to increase fuel cell robustness, decrease the H 2 purity requirements and ease the transition from H 2 derived from natural gas to H 2 produced from water and renewable energy sources.