PDA-assisted formation of ordered intermetallic CoPt3 catalysts with enhanced oxygen reduction activity and stability.

Structurally ordered intermetallic alloys with definite composition and distinct structure show great potential as electro-catalysts for the oxygen reduction reaction (ORR). However, their fabrication with small particle size remains a challenge since grain growth caused by high temperature annealing is unavoidable for the formation of the ordered phase. Here we propose an effective space-confined strategy to prepare an intermetallic alloy with small size (CoPt3/C-S) through annealing of the disordered Pt-Co alloy coated with polydopamine (PDA). The CoPt3/C-S intermetallic catalyst exhibits over 7-fold higher ORR activity and comparable stability compared to large intermetallic nanoparticles (CoPt3/C-L) prepared by direct heat-treatment without PDA. The superior ORR performance of the CoPt3/C-S catalyst can be attributed to the abundant active sites and unsaturated coordinated bonds caused by its special electronic structure, as proved by XPS and XAS tests. This work not only proposes a feasible synthesis route for small intermetallic nanoparticles but also provides a valid strategy to improve the ORR performance of ordered intermetallic catalysts.