Dual optimization for beaded iron diselenide/nickel diselenide-nitrogen‑doped carbon@carbon nanofibers...

Metal‑nitrogen-carbon (M-N-C) materials originating from prussian blue analogs (PBAs) are regarded as attractive catalysts toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Nevertheless, they suffer from drawbacks of poor conductivity and catalyst deactivation owing to metal aggregation. In this work, through a dual optimization strategy depending on structure regulation and interface engineering, we prepared a bead-like iron diselenide/nickel diselenide‑nitrogen-doped carbon@carbon nanofibers (FeSe₂/NiSe₂-NC@CNF) electrocatalyst with FeSe₂/NiSe₂-NC evenly anchored in the carbon nanofibers (CNF) one by one. FeSe₂/NiSe₂-NC@CNF demonstrates outstanding dual-functional electrocatalytic activity toward OER (E_j=10 = 254 mV, E_j=300 = 403 mV) and HER (E_j=450 = 601 mV) at high current densities. In addition, when applied to overall water splitting, the potential of FeSe₂/NiSe₂-NC@CNF at 10 mA·cm^-2 is only 1.63 V, indicating its outstanding water electrolysis capability. X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations indicate that the additional unsaturated coordinated NiSe bonds in FeSe₂/NiSe₂-NC@CNF are beneficial to optimizing the adsorption/desorption behaviors of intermediates and accelerating the rate-determining step (*O transforming into *OOH). The present study proposes a rational design strategy to optimize the performance of M-N-C catalysts, and lays the foundation for the advancement of superior bifunctional non-noble metal catalysts toward overall water electrolysis.