Regulation and mechanism study of the CoS2/Cu2S-NF heterojunction as highly-efficient bifunctional electrocatalyst for oxygen reactions

The precise design and controllable manufacture of electrocatalysts for efficient oxygen reactions (OER and ORR) based on the abundant elements of the earth are urgently required but challenging task. In this study, a CoS2/Cu2S heterostructured composite (CoS2/Cu2S-NF) supported by the porous carbon nanofibers is synthesized as a high-efficiency oxygen reaction electrocatalyst. As indicated from in-situ characterization methods (infrared, Raman and XRD) integrated with the density functional theory results, the heterostructures exhibited by CoS2 and Cu2S could be regulated. The results show that the electron transfer/interaction between CoS2 and Cu2S in the heterojunction were regulated, as well as the electronic structures of Co and Cu sites. As impacted by the structural engineering and the electronic modulation, the activity was enhanced, and the performance of electrocatalytic oxygen reactions was improved, which exhibited the lowest potential difference for (ΔE = 0.73 V) compared with commercial electrocatalysts. The liquid ZAB in accordance with on CoS2/Cu2S-NF exhibited a stable charge and discharge capacity up to 590 h and a great power density reaching 260.60 mW cm−2. Moreover, the flexible solid-state ZAB based on CoS2/Cu2S-NF exhibited a great competitive power density (92.06 mW cm−2), robust flexibility and an obvious integration. As compared with single metal sulfide-NF, the Density functional theory calculations (DFT) highlight the adsorption on CoS2/Cu2S-NF side surface in the heterojunction, which more specifically demonstrates the synergistic effect in the junction. This work presents a direction for designing heterostructured junctions as electrocatalyst and moreover its great application potential in rechargeable metal-solid batteries.