Tailoring the interfacial active center of MnSxO2−x/MnCo2S4 heterostructure to boost the performance for oxygen evolution reaction and Zn-Air batteries in neutral electrolyte

Abstract

Tailoring interfaces in heterostructured electrocatalysts is an optimal strategy for improving the electrocatalytic performance, yet determining which active center to adjust is still extremely challenging. Herein, we report a facile approach to construct a novel heterostructured electrocatalyst of MnSxO2−x/MnCo2S4. The density and structure of the active centers were fine-tuned by controlling the S-O atomic ratio on the surface of MnSxO2−x. Consequently, the optimized MnS0.10O1.90/MnCo2S4 sample had excellent oxygen evolution reaction performance, with overpotential of 367 mV @ 50 mA cm−2 in 1.0 M KOH. More impressively, in 0.2 M phosphate buffer solution, the overpotential @ 10 mA cm−2 is only 414 mV. Furthermore, as the air–cathode catalyst in neutral zinc-air batteries, MnS0.10O1.90/MnCo2S4 exhibited excellent stability with the round-trip efficiency decaying by only 3.8% at 10 mA cm−2 after 140 h. Theoretical calculations revealed that Mn-Co site has the suitable binding affinity to the oxygen-containing intermediates, neither too weak (Mn site) nor too strong (Co-Co site), while MnCo2S4 endows the oxidized CoMnO active species a tensile strain that decreases the overpotential. This study opens an avenue for developing high-performance and durable heterostructure electrocatalysts toward OER, metal-air batteries in neural electrolytes and beyond.