铜-镍合金电极表面组成及状态的变化对硝基苯电还原的影响

铜-镍合金电极表面组成及状态的变化对硝基苯电还原的影响;Monel合金电极;表面状态;硝基苯;对氨基苯酚;电还原

The Effect of Surface Composition and State of Cu-Ni Alloy on Electrochemical Reduction of Nitrobenzene to p-Aminophenol

In the investigations of electrochemical reduction of nitrobenzene to p-aminophenol at the Monel alloy electrode, it was found that the yield gradually decreased with the increase of the service time of the Monel alloy electrode. At the initial stage of reaction, the yield of p-aminophenol at the Monel electrode was 75. 2% , which was close to that at the Cu-Hg electrode. Within 500 h service time, the yield could be maintained above 70%. However, the yield decreased greatly to 63. 1% after 800 h service, which was close to that at the Cu electrode. In order to figure out the reasons of the decrease, the Monel alloy electrodes before and after service were characterized by means of X-ray diffraction ( XRD) , scanning electron microscopy (SEM) , energy dispersive X-ray spectroscopy ( EDS) and the electrochemical method. The results from the XRD indicate that the surface unit cell composition of the Monel alloy electrode had significant variations after 800 h service, compared with that of the electrode before service. The results from the SEM and EDS show that the changes of the surface composition and state of the Monel alloy electrode were caused by the surface element enrichment of Cu, they were the main reasons for the deterioration of electrocatalytic properties of the electrode in the electrochemical reduction of nitrobenzene. The results from steady-state polarization confirm the conclusion further.