Cobalt sulfides constructed heterogeneous interfaces decorated on N,S-codoped carbon nanosheets as a highly efficient bifunctional oxygen electrocatalyst

The rational design and controllable synthesis of excellent bifunctional oxygen reduction and evolution reaction (ORR/OER) electrocatalysts are of vital importance for zinc-air battery applications. Herein, we report nitrogen/sulfur-codoped carbon nanosheets (NSC) decorated with dense Co9S8/Co1-xS heterostructures (Co9S8/Co1-xS@NSC), prepared by a one-pot salt template-assisted pyrolysis procedure. The population of the Co9S8/Co1-xS heterostructure can be effectively controlled by tuning the precursor components. Salt templates constructed hierarchical porosity for the wide-open carbon nanosheets, which maximized the N functional groups to anchor highly dispersive Co9S8/Co1-xS species. Experiments and theoretical simulations revealed notable electronic interactions within Co9S8/Co1-xS interfaces, which can effectively optimize the adsorption/desorption behaviors of intermediates in ORR/OER, thus promoting the bifunctional electrocatalytic performance. The half-wave potential for the ORR of 0.86 V and the OER electrocatalytic potential of 1.52 V at 10 mA cm(-2) were obtained. Benefiting from the strong coupling effect between the Co9S8/Co1-xS species and the carbon substrate, superior durability was obtained for 2000 ORR/OER cycles. The practical zinc-air battery based on the Co9S8/Co1-xS@NSC cathode manifested a high open-circuit voltage, small voltage gap and robust reversibility. Our study revealed the great potential of the bi-elemental (Co and S) heterostructure in enhancing the ORR/OER activity, which suggests a logical extension to other electrocatalysis systems.

Automated summary

The study presents a novel electrocatalyst composed of nitrogen/sulfur-codoped carbon nanosheets decorated with Co9S8/Co1-xS heterostructures, prepared by a salt template-assisted pyrolysis method. The heterostructure enhances the adsorption/desorption behaviors of intermediates in oxygen reduction and evolution reactions, leading to improved bifunctional electrocatalytic performance.