Dual-site polydopamine spheres/CoFe layered double hydroxides for electrocatalytic oxygen reduction reaction

Development of efficient and low-cost electro-catalysts for the oxygen reduction reaction (ORR) has been a great challenge for fuel cells and metal-air batteries. Here the hybrids of CoFe layered double hydroxides (CoFe-LDHs) with polydopamine spheres (PDAS) were prepared by growing CoFe-LDHs at the surface of PDAS in situ and their catalytic activity toward the ORR was investigated in detail. The results show that the as-prepared CoFe-LDHs/PDAS hybrids exhibited higher ORR catalytic activity with 4e-route selectivity than pure CoFe-LDHs, PDAS and even calcinated CoFe-LDHs/PDAS, which displays synergistic effect between CoFe-LDHs and PDAS for ORR. Moreover, the CoFe-LDHs/PDAS hybrids demonstrated better durability than commercial Pt/C ORR catalysts. To uncover the ORR mechanism, the interaction between CoFe-LDHs and PDAS were characterized by XPS and the ORR activity of CoFe-LDHs/PDAS and CoFe-LDHs/PDAS leached with acid was compared. The catalytic behavior of CoFe-LDHs/PDAS hybrids is consistent with a dual-site ORR mechanism.