Hollowed structured PtNi bifunctional electrocatalyst with record low total overpotential for oxygen reduction and oxygen evolution reactions

Oxygen electrocatalysis plays a critical role in numerous energy storage/conversion devices, but the sluggish kinetics of both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has greatly restricted the broad-based applications of such devices, especially for those requiring bifunctional electrocatalysts towards both reactions (e.g., regenerative fuel cells, metal-air batteries). Herein, we demonstrate that hollow structured bimetallic PtNi/C synthesized through a facile solution-based approach can be employed as a highly active bifunctional electrocatalyst for both ORR and OER, showing a combined ORR and OER overpotential of 0.69 V, which represents a record low value for a bifunctional electrocatalyst. Rotating ring disk electrode (RRDE) technique discloses that ORR was proceeding predominantly through the desired 4-electron pathway on the PtNi/C catalyst. Moreover, the PtNi/C is also found rather stable for both ORR and OER, with small activity lost after the accelerated durability test. These data echo the importance of innovative bi-/multi-metallic nanostructures for highly efficient catalysts that depend critically on using precious metals, for application in energy storage/conversion technologies.