Recent advancements in electrode design are substantially linked to state-of-the-art nanomaterial fabrications. Herein, we report a simple one-pot hydrothermal synthesis of Cd(OH)₂ with a platelet-like morphology, which was subsequently annealed at relatively high temperatures to produce a CdO/Cd(OH)₂ nanocomposite for the first time. It was found that the control of thermal treatment allowed tunable charge transport across the nanometre scale due to the presence of CdO and Cd(OH)₂ mixed nanocrystals. The CdO/Cd(OH)₂ nanocrystals offer interesting prospects for the electrocatalytic oxidation of nitrite ions and for supercapacitor applications. The CdO/Cd(OH)₂ nanocomposite was blended with a trace amount of gold NPs for enhancing the electrochemical conductivity and electrocatalytic capability for nitrite oxidation with a sensitivity of 32.9 μA mM⁻¹. It afforded a promising electrocatalyst in a wide concentration range up to 10 mM with a low detection limit of 0.87 μM. Furthermore, the CdO/Cd(OH)₂ nanocomposite electrode was showed to be a highly active and stable supercapacitor, achieving a high specific capacitance in an alkaline medium of about 145 F g⁻¹ at a discharge current of 2.0 A g⁻¹. These results have revealed that the presence of mixed oxide/hydroxide nanocrystals in nanoscale dimensions will be very interesting for various electrochemical applications and provide for a new class of nanodevices based on electrochemistry with unique capabilities.