Surface reconstruction of pyrite-type transition metal sulfides during oxygen evolution reaction

Reconstruction universally occurs over non-layered transition metal sulfides (TMSs) during oxygen evolution reaction (OER), leading to the formation of active species metal (oxy)hydroxide and thus significantly influences the OER performance. However, the reconstruction process and underlying mechanism quantitatively remain largely unexplored. Herein, we proposed an electrochemical reaction mechanism, namely sulfide oxidation reaction (SOR), to elucidate the reconstruction process of pyrite-type TMSs. Based on this mechanism, we evaluated the reconstruction capability of NiS₂ doped with transition metals V, Cr, Mn, Fe, Co, Cu, Mo, Ru, Rh, and Ir within different doped systems. Two key descriptors were thus proposed to describe the reconstruction abilities of TMSs: U_SOR (the theoretical electric potential of SOR) and ΔU (the difference between the theoretical electric potential of SOR and OER), representing the initiation electric potential of reconstruction and the intrinsic reconstruction abilities of TMSs, respectively. Our finding shows that a lower U_SOR readily initiate reconstruction at a lower potential and a larger ΔU indicating a poorer reconstruction ability of the catalyst during OER. Furthermore, Fe-doped CoS₂ was used to validate the rationality of our proposed descriptors, being consistent with the experiment findings. Our work provides a new perspective on understanding the reconstruction mechanism and quantifying the reconstruction of TMSs.