In this work, a novel sensing scaffold, consisting Au nanoparticle (GNP)–dotted TiO₂ nanotubes (TNTs) as the rigid material and the hydrophobic ionic liquid (HIL), 1-decyl-3-methylimidazolium tetrafluoroborate, as the entrapping agent, was applied to facilitate the electron transfer of horseradish peroxidase (HRP) on a glassy carbon electrode. GNPs were immobilised on the TNTs in our work using a one-step reduction of HAuCl₄·3H₂O by sodium borohydride in the presence of sodium citrate as a stabilising reagent. The morphology and composition of the as-synthesised composite materials were characterised by transmission electron microscopy, scanning electron microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy. Cyclic voltammetry of HRP at the modified electrode presented a pair of reproducible, quasi-reversible redox peaks with a peak-to-peak separation of 69 mV, indicating electron transfer between HRP and composite electrode. The GNP–TNT|HIL|HRP electrode was then applied to the detection of H₂O₂ in a pH 7.0 phosphate buffer using chronoamperometry. The biosensor exhibited a linear response in the 15–750 μM range, and a limit of detection of 2.2 μM. The biosensor also exhibited stability with 90% of the detection signal retained over a two-week duration.