Electrochemical measurements. The electrochemical testing was measured by CHI 760E electrochemical workstation (CH Instruments Inc.) at room temperature. For HER testing, cyclic voltammetry (CV) and LSV curves were obtained in a three-electrode cell setup, consisting of a glassy carbon disk electrode (GCE, diameter 5 mm, surface area 0.07 cm² ) as the working electrode, polished with alumina slurry and cleaned with ethanol and deionized water. A carbon rod served as the counter electrode, and an Ag/AgCl electrode in 0.5 M H₂SO₄ was used as the reference electrode. The potential of the reference electrode was calibrated to the reversible hydrogen electrode (RHE) using: ERHE= EHg/HgCl2 + (0.244 + 0.0591 × pH) V in 0.5 M H2SO4 solution. The working electrode for HER was prepared by dissolving 1 mg of carbon nanotube and 1 mg of Au25 NCs in 0.5 mL of CH2Cl2, creating an ink with 10 µL of 5 wt% Nafion. Before testing, 3.5 µL of the catalyst and 3 µL of Nafion (5 wt%) were cast onto the GCE.