Facile Synthesis of Low and Non-Precious Metal Nanocatalysts for Oxygen Reduction Reaction in Fuel Cells

Abstract

The considerable interest in polymer electrolyte membrane fuel cells (PEMFCs) has sparked sustained research efforts on more active and stable oxygen reduction reaction (ORR) electrocatalyst. Although great progress has been made on ORR catalysts in recent decades, the further development of PEMFCs is severely restrained by high-priced Pt catalysts and the slow kinetics of the ORR on cathode. Control of nanostructures at the atomic level can precisely and effectively tune catalytic properties of catalysts, optimizing the structural and compositional effect and further enabling enhancement in both activity and durability. Therefore, constructing novel nanocatalysts with low and non-Pt group metal (PGM) has received significant attention to further enhance ORR electrocatalytic performance. Combining structural, morphological and compositional features, Pt-based alloys with optimized composition and unique structures are expected to present enhanced electrocatalytic performance and economical advantages. On one hand, the electron structure of Pt is modified by the non-precious metals when Pt-based alloys are formed. This modification is efficient to weaken the binding energy between Pt and the adsorbed hydroxyl species. Therefore, more active sites are released, and thus improve the electrocatalytic performance. On the other hand, Pt-based nanocrystals with complex morphologies are promising in catalyzing ORR in fuel cells. The cost of catalyst can be further reduced by completely getting rid of platinum using non-precious metal nanocatalysts or metal-free nanomaterials. In addition, by introducing heteroatoms, metals, and metal oxides, more active sites are formed for oxygen reduction reactions, and thus improve the catalytic performance of the catalysts. Significantly, these low and non-precious metal nanocatalysts show excellent electrocatalytic activity and high stability toward to the ORR, holding great promise for the development of PEMFCs.