Gold nanoparticles (AuNPs) anchored carbon-nanomaterial chemically modified electrodes have been widely used for electrocatalytic applications. Indeed, only a fraction of AuNPs surface is found to be active, while most of the surface is inactive in nature. Thus, it is a challenging research to prepare active AuNPs suitable for electrocatalytic applications. Herein, we present a low-cost intrinsic nickel-containing carbon black (CB-Niint, int= intrinsic nickel) modified glassy carbon electrode as an efficient matrix for forming highly active AuNPs (GCE/CB-Niint@AuNPs). Specific electrocatalytic oxidation of hydrazine has been used as a model system to compare the active sites of the AuNPs. Various carbon nanomaterials like SWCNT, MWCNT, carbon nanofiber, and graphite nanopower-modified electrodes and externally deposited Ni (Niext) on the carbon-modified electrodes were examined as controls for the AuNPs formation and hydrazine electrocatalytic activity. Amongst all, the CB-Niint matrix-modified electrode has shown the best electrocatalytic activity. The GCE/CB-Niint@AuNPs was subjected to various physicochemical characterizations like FESEM, TEM, Raman, IR, XPS, and scanning electrochemical microscopy (SECM) using a Eu3+/2+ redox probe. Meanwhile, with Fe(CN)63−, ex-situ derivatization of Niext as Ni-hexacyanoferrate, CB@Niext-HCF, was specifically inferred. It has been revealed that AuNPs form an intrinsic Au-Niint alloy system on the interstitial position of CB-Niint. On the other hand, a bulk layer-like AuNPs morphology was observed with the CB-Niext modified electrode case. This unique structural feature of the CB-Niint@AuNPs sets a new trend in AuNPs-based chemically modified electrode preparation and electrochemical applications. As a proof of concept, selective electrochemical sensor application of hydrazine with a current sensitivity of 4.37 mA mM−1 cm−2, which is about 5-10 times higher than the majority of the conventional AuNPs-modified electrodes, without any common interference from H2O2, uric acid, ascorbic acid, dopamine, and cysteine, was demonstrated.