Exploration of cost-effective Pt/C catalysts has been a significant issue for electrochemical hydrogen evo-lution reaction(HER)toward sustainable energy conversion and storage.Herein,we report a fabrication strategy by employing platelet carbon nanofibers(p-CNF)as the support to immobilize Pt-CoO HER elec-trocatalyst using atomic layer deposition method.The edge-rich p-CNF support is found to act as the anchoring sites of Pt nanoparticles and favorably capture electrons from Pt to yield electron-deficient Pt surfaces for the boosted HER.Additionally,the sequential growth of CoO onto the Pt/p-CNF catalyst elab-orately constructs the Pt-CoO interface and facilitates the electron transfer from Pt to CoO,which further enhances the HER activity.These advantages endow the fabricated Pt-CoO/p-CNF catalyst with the supe-rior HER activity,e.g.,a very low overpotential of 26 mV at the current density of 10 mA?cm-2 and a mass activity of 4.42 A·mgpt-1 at the overpotential of 30 mV,18.8 times higher than that of the commercial 20 wt％Pt/C catalyst.The insights reported here could shed light on for the fabrication of cost-effective Pt-based composite HER catalysts.