PtCo Nanoalloy Co-Doped Atomically Dispersed Co-N4 Catalyst for Oxygen Reduction in Fuel Cell

Abstract

Fuel cells are the trending renewable energy source for sustainable future; however, the insufficient performance of Pt-based cathode catalysts particularly, the limited durability hampers their broader applications. Recently, Pt nanoalloys and transition metal-based single-atom catalysts have been emerging catalysts for ORR in fuel cells. However, the high cost of the Pt group metals (PGM) and the limited performance of non-PGM catalysts are huge challenges to meet the desired performance of the fuel cells. Here we report a PtCo nanoalloy catalyst encased by the atomically dispersed Co-N4 doped graphitic carbon nanosheets for the oxygen reduction reaction. The catalyst is prepared by a facile molten salt synthesis method to confine PtCo nanoalloy into atomically dispersed Co and nitrogen co-doped graphitic carbon nanosheets through high-temperature annealing. The catalyst is a unique combination of PtCo nanoparticles and atomically dispersed Co-N4 in a modified carbon nanosheets matrix which endows a synergistic response leading to a high oxygen reduction activity and stability. The as-prepared PtCo@gCNS nanoparticles along with atomically dispersed Co-N4 active sites possess remarkable oxygen reduction performance demonstrating a mass activity of 1.268 AmgPt -1 and superior durability with a negligible decay after 30000 potential cycles. Density functional theory calculations reveal the richly accessible PtCo nanoalloy and atomically dispersed Co-N/C in the ultra-thin graphitic carbon nanosheets as dual active sites responsible for the improved ORR performance. Moreover, ultra-thin graphitic carbon nanosheets provide enhanced electronic conductivity and mass transport, while carbon-coated architecture provides improved durability against catalyst nanoparticles dissolution. Such a unique and multi-components catalyst system with PtCo nanoalloy, Co-N4 single atomic sites and upgraded carbon support altogether provide an effective ORR catalyst. The synergistic catalysis resulting from the atomically dispersed Co-N4 single atomic sites and PtCo nanoparticles engrossed in graphitic carbon nanosheets through a facile and scalable synthesis approach could step up the realistic applications of oxygen electrocatalysts in practical fuel cells. Figure 1