Enhanced Heterogeneous\nInterfacial Coupling of NiCoS@NiCo(CH<sub>3</sub>COO)<sub><i>x</i></sub> as Efficient and Long-term\nStable Electrocatalysts for Oxygen Evolution Reaction

Regulating the interfacial coupling of core–shell\nstructured\nelectrocatalysts is critical for enhancing the electrocatalytic performance\ntoward oxygen evolution reaction (OER). In this work, 1D NiCo-LDH\n(layered double hydroxide) and NiCo oxides were selected as a model\nto study the effect of interlamellar bonding strength on the structure\nand performance of the as-synthesized 1D NiCoS@NiCo(CH<sub>3</sub>COO)<sub><i>x</i></sub> (NCS@COAC). It was revealed that\nthe sulfides obtained from NiCo-LDH and NiCo oxide exhibit different\ncrystallinities, which in turn diversifies the morphology of NCS@COAC\nand P-NCS@COAC. In particular, the low crystallinity of NCS results\nin the Kendall effect between CH<sub>3</sub>COO<sup>–</sup> and S<sup>2–</sup>, leading to the formation of a hierarchical\ncore–shell structure of NCS@COAC that is composed of nanorod\nand nanotube structures. The appearance of nanotubes increases the\nratio of accessible active sites, facilitating the proceeding of the\nOER. In addition, the interaction between CH<sub>3</sub>COO<sup>–</sup> and S<sup>2–</sup> regulates the local chemical environment\nof Co/Ni, increasing the density of high-valent Co, especially for\nNCS@COAC obtained from hydroxides. Moreover, the formation of a core–shell\nstructure also inhibits the leaching of S<sup>2–</sup> in the\nOER, which is beneficial for maintaining the 1D core–shell\nstructure. As a result, NCS@COAC delivers a decreased overpotential\nof 23 mV lower than that of P-NCS@COAC at the current density of 20\nmA cm<sup>–2</sup> and superior stability with retention of\nthe original current after testing for 100 h.