The morphology or shape of nanomaterials plays an important role in functional applications, especially in the electrochemical sensing performance of nanocomposites modified electrodes. Herein, the morphology-dependent electrochemical sensing properties of MnO₂-reduced graphene oxide/glass carbon electrode (MnO₂-RGO/GCE) toward dopamine detection were investigated. Firstly, various morphologies of nanoscale MnO₂, including MnO₂ nanowires (MnO₂ NWs), MnO₂ nanorods (MnO₂ NRs), and MnO₂ nanotubes (MnO₂ NTs), were synthesized under different hydrothermal conditions. Then the corresponding MnO₂-RGO/GCEs were fabricated via drop-casting and the subsequent electrochemical reduction method. The oxidation peak currents increase with the electrochemical activity area following the order of MnO₂ NWs-RGO/GCE, MnO₂ NTs-RGO/GCE, and MnO₂ NRs-RGO/GCE. The spatial models for MnO₂ NWs, MnO₂ NTs, and MnO₂ NRs are established and accordingly compared by their specific surface area, explaining well the evident difference in electrochemical responses. Therefore, the MnO₂ NWs-RGO/GCE is selected for dopamine detection due to its better electrochemical sensing performance. The response peak current is found to be linear with dopamine concentration in the range of 8.0 × 10⁻⁸ mol/L–1.0 × 10⁻⁶ mol/L and 1.0 × 10⁻⁶ mol/L–8.0 × 10⁻⁵ mol/L with a lower detection limit of 1 × 10⁻⁹ mol/L (S/N = 3). Finally, MnO₂ NWs-RGO/GCE is successfully used for the determination of dopamine injection samples, with a recovery of 99.6–103%. These findings are of great significance for understanding the relationship between unlimited nanoparticle structure manipulation and performance improvement.

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