In this contribution, a voltammetric enzyme-free sensor based on Co3O4 @carbon composites was developed to detect catechol and hydroquinone simultaneously. Glucose was skillfully exploited as a cheap carbon source for the fabrication of Co3O4 @carbon core/shell nanostructured composites via a hydrothermal process followed by calcination treatment. The Co3O4 @carbon core/shell nanostructure embodies good catalytic activity of Co(3)O(4 )and superior conductivity of carbon layer, making it possible to detect hydroquinone and catechol simultaneously. The binary composites showed superior electrochemical performances than each of the component. The fabricated Co3O4 @carbon based sensor presented broad linear concentration range of 0.8-127.1 mu M and 0.6-116.4 mu M for hydroquinone and catechol, respectively. The prepared sensor also possessed a rather low detection limit of 0.03 mu M for both of them, with satisfying repeatability, reproducibility, stability in the determination of catechol and hydroquinone, and excellent recovery in real sample test. The obtained results suggest that the Co3O4 @carbon modified electrode has great potential application for sensing catechol and hydroquinone simultaneously. (C) 2019 The Electrochemical Society.