Noble-metal-free Co₃S₄-S/G porous hybrids as an efficient electrocatalyst for oxygen reduction reaction

Developing of a new noble-metal-free catalyst to replace Pt-based catalysts of the oxygen reduction reaction (ORR) both in alkaline and acidic conditions is extremely significant for the fuel cell. In this paper, based on the pyrolysis of an inexpensive precursor cobalt dithiolene (a S₄-chelate complex) on simultaneously reduced graphene oxide (GO) as a support matrix, a high-efficiency noble-metal-free hybrid for oxygen reduction reaction (ORR) consisting of Co₃S₄ nanoparticles encapsulated in porous sulfur doped graphene (referred as Co₃S₄-S/G) was fabricated. The catalyst obtained at 800 °C (Co₃S₄-S/G-800) manifests excellent oxygen reduction activity. Of note, the Co₃S₄-S/G-800 hybrids also exhibited prominent ORR activity with high selectivity (mainly 4e^- reaction process) and very low H₂O₂ yield in acidic electrolyte. The optimal Co₃S₄-S/G-800 hybrid displayed much greater tolerance to methanol and higher stability than that of Pt/C. These admirable performances endorse Co₃S₄-S/G-800 electrocatalyst holding great potential for fuel cells. Meanwhile, this work also provides a simple and practical method to fabricate cobalt chalcogenides by using the cost-effective and easily synthesized S₄-chelate complex.