1：Experimental Design and Method Selection:

A facile method involving electrochemical deposition followed by in situ nitridation was used to fabricate 3D NiCo-nitrides nanoparticles/NiCo2O4 nanoflakes/graphite fibers. The design rationale was to create a hybrid structure with metallic components to enhance electron transfer and catalytic activity.

2：Sample Selection and Data Sources:

Graphite fibers were used as the conductive substrate. Samples were characterized using SEM, TEM, XRD, XPS, XAFS, and electrochemical measurements.

3：List of Experimental Equipment and Materials:

Equipment included SEM, TEM, XRD, XPS, XAFS, electrochemical workstation, gas chromatography system (Labsolar-6A). Materials included nickel nitrate, cobalt nitrate, graphite fibers, NH3 for nitridation, electrolytes (1 M KOH, 0.5 M H2SO4, 1 M PBS).

4：5 M H2SO4, 1 M PBS). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Co-electrodeposition of nickel-cobalt hydroxides on graphite fibers, pyrolysis to form NiCo2O4, thermal ammonolysis for partial conversion to NiCo-nitrides. Electrochemical tests (LSV, Tafel, EIS) were conducted in a three-electrode system for HER and OER in various pH media.

5：Data Analysis Methods:

Data were analyzed using equivalent circuits for EIS, Tafel slopes from polarization curves, and DFT calculations for electronic structure analysis.