In situ embedding Co9S8 into nitrogen and sulfur codoped hollow porous carbon as a bifunctional electrocatalyst for oxygen reduction and hydrogen evolution reactions.

A novel in situ strategy to embed Co 9 S 8 nanoparticles into nitrogen and sulfur codoped hollow porous carbon (Co 9 S 8 @N-S-HPC) is achieved. The Co 9 S 8 @N-S-HPC can be used an efficient catalyst for both ORR and HER. The unique nanostructure and synergistic interactions between Co 9 S 8 and N-S-HPC play a crucial role to improve the electrocatalytic performance. • Co 9 S 8 @N-S-HPC is fabricated using a novel in situ formation approach. • Co 9 S 8 @N-S-HPC shows excellent electrocatalytic performance toward ORR and HER. • Synergistic effect of Co 9 S 8 and N-S-HPC improves the electrocatalytic performance. The oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) are critical processes for many energy conversion technologies, where efficient catalyst plays a key role in these reactions. Here we report a novel in situ strategy to embed Co 9 S 8 nanoparticles (NPs) into nitrogen and sulfur codoped hollow porous carbon (Co 9 S 8 @N-S-HPC). In this strategy, the ZIF-8 surface is firstly decorated by cobalt thiourea, and then coated with a shell of polymeric resorcinol-formaldehyde, followed by a high temperature pyrolysis treatment. The resulting Co 9 S 8 @N-S-HPC shows comparable catalytic activity for ORR compared with commercial 20 wt% Pt/C catalyst and superior long-term stability under alkaline conditions. Simultaneously, Co 9 S 8 @N-S-HPC also exhibits an excellent HER activity with low onset overpotential of 68 mV, a small Tafel slope of 78 mV per decade and a long-term durability in alkaline medium. First-principles calculations reveal that Co 9 S 8 particle can anchor in N-S-HPC via a Co-S bond and enhance the binding of Co 9 S 8 and N-S-HPC. The N-S-HPC can affect the electronic structure of supported Co 9 S 8 strongly. The combined experimental and theoretical investigation show the outstanding ORR and HER performances of Co 9 S 8 @N-S-HPC are attributed to its unique nanostructure and synergistic interactions between Co 9 S 8 NPs and N-S-HPC. [ABSTRACT FROM AUTHOR]