Study of the ReS₂-CoO/CoS₂ Heterostructure for Efficient Bifunctional Electrocatalysis

Heterogeneous interfaces are an effective strategy to modulate interfacial properties and enhance catalytic functionality. However, their dynamic evolution under reaction conditions remains elusive, hindering rational catalyst design. Herein, we report a ReS2-CoO/CoS2 heterostructure to investigate its structural transformation under electrocatalytic water splitting conditions, as well as to modulate its activity and stability. Electrochemical measurements reveal exceptional bifunctional catalytic activity, with overpotentials of 25 mV for HER (at 10 mA·cm⁻²) and 241 mV for OER (at 50 mA·cm⁻²). The synergistic interfacial interaction substantially enhances the kinetic processes. The integrated interface between CoO and CoS2 on ReS2 not only ensures intimate electronic coupling but also facilitates abundant surface defect formation, as confirmed by FTIR, XPS, and EPR analyses. In-situ Raman spectroscopy demonstrates structural robustness during HER, whereas a significant surface reconstruction occurs during the OER, in which the initial CoO/CoS2 phase transforms into CoO/CoOOH, serving as the new active species. The catalyst achieves efficient overall water splitting performance (1.43 V at 10 mA‧cm⁻2) with sustained performance. These findings offer valuable insights into interfacial engineering strategies for the rational design of advanced electrocatalysts.