▎ 摘　　要

Understanding the sensing reaction mechanism at the solid electrode-liquid electrolyte interface during the detection is crucial for developing chemical sensors. In this work, layered MnO2 nanosheets were coated on nitrogen-doped reduced graphene oxide aerogel (3D-N-rGO) rotating disk electrode (RDE) and used towards hydrazine detection. The successive reduction in the oxidation number of Mn in the MnO2/3D-N-rGO electrode during the detection monitored by an in situ electrochemical X-ray absorption spectroscopy (XAS) indicates that 0.15 mol electrons produced from the oxidation of hydrazine do transfer to MnO2. The hydrodynamic diffusion of hydrazine from bulk solution to the surface of the MnO2/3D-N-rGO RDE investigated also plays a major role in the sensitivity of hydrazine detection. The limit of detection (LOD) value at a signal-to-noise ratio of ca. 3 is 085.0 mu M (4000 rpm) with a response time of < 2 s and wide linear concentration ranges. The MnO2/3D N-rGO RDE can detect trace hydrazine without any effect of high concentration interferences (20-100 mu M) including glucose, caffeine, methylamine, ethylenediamine, n-butylamine, adenine, cytosine, guanine, and L-arginine. In addition, the MnO2/3D N-rGO RDE sensor can practically be used to detect trace hydrazine in real-world samples i.e., drinking water and lake water.