Surface Reconstruction of Covellite CuS Nanocrystals for Enhanced OER Catalytic Performance in Alkaline Solution

Oxygen evolution reaction (OER) is one of the important half-reactions in energy conversion equipment such as water-spitting devices, rechargeable metal-air batteries, and so on. It is beneficial to develop efficient and low-cost catalysts that understand the reaction mechanism of OER and analyze the reconstruction phenomenon of transition metal sulfide. Interestingly, copper sulfide and cuprous sulfide with the same components possess different reconstruction behaviors due to their different metal ion valence states and different atomic arrangement modes. Because of a unique atomic arrangement sequence and certain cationic defects, the reconstruction phenomenon of CuS nanomaterials are that S²⁻ is firstly oxidized to SO₄²⁻ and then Cu^x+ is converted into CuO via Cu(OH)₂. In addition, the specific “modified hourglass structure” of CuS with excellent conductivity is easier to produce intermediates. Compared with Cu₂S, CuS exhibits excellent OER activity with a lower overpotential of 192 mV at 10 mA cm⁻² and remarkable electrochemical stability in 1.0 m KOH for 120 h. Herein, this study elucidates the reconstruction modes of CuS and Cu₂S in the OER process and reveals that CuS has a stronger Cu S bond and a faster electronic transmission efficiency due to “modified hourglass structure,” resulting in faster reconstruction of CuS than Cu₂S.