3.3. Electrocatalytic oxidation of N2H4 Zero current potentiometry is a novel electrochemical approach for in situ probing changes of the interfacial potential [41]. This approach had been successfully applied for the study of the surface acid–base property of functionalized carbon nanotubes [42] and the self-assembly of l-cysteine on gold surface [41]. It will provide a powerful tool for the study of more interfacial processes of other compounds on new conductive materials. In the proposed approach, the external electrolysis circuit of traditional three electrode potentiostat is re-equipped by connecting in series a conductive substrate between two clips of working and counter electrodes, and a reference electrode is still connected with the clip of reference electrode. Here, zero current potentiometry was employed for the study of electrocatalytic oxidation of N2H4 on the PtNPs/nanoZnO/GCE. The interface potential strongly depends on the property of the sensing surface and the solution composition. When the PtNPs/nanoZnO/GCE and the reference electrode were immersed into a blank 0.1 M pH 7.0 sodium phosphate buffered saline (PBS), a zero current potential Ezcp was gotten at −0.146 V, as shown in Fig. 5 curve a. With the addition of N2H4 (shown in Fig. 5 curve a–e), Ezcp decreased linearly. The variation reflected the interface interaction happened as following [43]:
N2H4→N2 +2H2