Dual Active Sites Engineering on Sea Urchin-Like CoNiS Hollow Nanosphere for Stabilizing Oxygen Electrocatalysis via a Template-Free Vulcanization Strategy

摘要

Manipulating electronic structure and defects is crucial to achieve on-demandfunctionalities of bimetallic sulfide catalysts for oxygen reduction/evolutionreactions (ORR/OER). Here, via a vulcanization strategy, defects-abundantNiCo_2S_4 needles obtained from sea urchin-like NiCo_2O_4 are anchored on surfaceof hollow carbon-sphere (NiCo_2S_4/HCS). NiCo_2S_4 nanoneedles (≈7.5 nm)are radially grown on shell of HCS with a cavity (254.5 m~2 g~(?1)), and theirsurface becomes rougher after vulcanization due to anion exchange reaction.As-marked NiCo_2S_4/HCS-3 exhibits better ORR activity (half-wave potentialof 0.89 V) and methanol tolerance than Pt/C (0.86 V). NiCo_2S_4/HCS-3 showsa lower OER overpotential (310 mV) than RuO_2 and retains 90.9 of initialactivity after 9 h. Notably, zinc–air battery with NiCo_2S_4/HCS-3 reveals highlystablecharging/discharging voltages of 2.11/1.16 V with a negligible fading for200 h. NiCo_2S_4 grown on outer/inner surfaces of HCS expands spatial distributionof active sites to enhance reactants-electrode contact and charge transfer.Theoretical calculation shows that Co-site with an electronic state near Fermienergy level is chiefly-responsible for ORR, while Ni-site mainly affords highOER activity. Bader charge analyses reveal that S doping increases the chargedensity and redox active sites in NiCo_2S_4. It sheds light on the understandingof electrocatalytic mechanisms on bimetallic sulfides for electronic device.