Enhancing bifunctional oxygen electrocatalysis with in-situ etching of oxide overlayers on sulfur-vacancy enriched CuCo2O4/CuCo2S4

Transition metal sulfide (TMS) are considered promising alternatives to noble metals for high-efficiency oxygen reduction and oxygen evolution (ORR/OER). However, traditional preparation methods or post-treatment processes can lead to the formation of oxide overlayers on the TMS catalysts, which can hinder their electrochemical performance. Herein, a sulfur-vacancy enriched CuCo2O4/CuCo2S4 heterostructure was prepared using cold plasma. Plasma also achieved the in-situ etching of oxide overlayers on the surface of catalysts. There is a strong correlation between the oxide overlayers and ORR/OER activity. Specifically, the number of ORR electrons transferred increased (n: from 2.8 to 3.7), while the OER overpotential decreased (eta: from 417 to 330 mV) in 0.1 M KOH with the decrease of the oxide overlayer concentration (SO2 �4 /SM_S: from 1.795 to 0.798). The theoretical calculation reveals the influence of oxide overlayers and S vacancy on the binding energy of the intermediate. The findings suggest that this work provides a new idea for designing metal sulfide electrochemical catalyst.

Automated summary

In this study, a sulfur-vacancy enriched CuCo2O4/CuCo2S4 heterostructure was successfully prepared using cold plasma, and in-situ etching of oxide overlayers on the catalyst surface was achieved. The results reveal that decreasing the concentration of oxide overlayers can increase the number of ORR electrons transferred and decrease the OER overpotential.