Study On Molding Technology And Desalination Performance Of Polypyrrole/Carbon Nanotube Electrode

As a novel desalination technology, capacitive deionization(CDI), also called electrosorption, has attracted more and more attention due to its significant advantages such as no secondary pollution, low operating cost. The desalination performance and practical application of CDI depend a lot on the capability of electrodes which act as the kernel of CDI technology. The molding technology of electrodes is one of the key factors affecting the capability of electrodes. So, from the point view of practical applications, it is necessary to study the molding technology of composite material electrodes.In the paper, polypyrrole/carbon nanotubes(PPy/CNT) composite material, polyvinylidene fluoride(PVDF) and graphite powder were used as active material, binder and conductivity agent, respectively. The influences of the component ratios on the performance of the PPy/CNT electrodes fabricated by coating molding method were investigated. The results indicated that the obtained PPy/CNT electrodes with the mass ratio of 12:1:1(mPPy/CNT : mPVDF : m graphite) has the best performance and presents porous and uniform structure, its specific mass adsorption capacity is about 117.4 mg/g, which is 2 times that of activated carbon electrodes.The influences of the component ratio, the moulding pressure and the film thickness on the performance of the PPy/CNT electrodes fabricated by compression molding method were also investigated. The results indicated that the obtained PPy/CNT electrodes with the mass ratio of 9:1:2(mPPy/CNT : mPVDF : m graphite) has the best performance, its specific mass adsorption capacity is about 5 times that of CNT electrodes. The PPy/CNT electrode fabricated at moulding pressure of 10 MPa is the best option. The overall performance of the electrode is increased and then decreased with the increase of the thickness of electrode film. The electrode with thickness of 0.59 mm has the best performance, its specific mass adsorption capacity reached a maximal value of 53.6mg/g. Comparatively, the coating method is more competitive than the compression according to the desalination performance of the obtained electrodes.The desalination stability of the electrodes was studied between the coating molding method and compression molding method. The results indicated that the declining rate of capacitance performance of the former is as high as 70 percent after 500 times of cyclic voltammograms scan at scanning rate of 10mV/s and that of the latter is only around 12 percent. Compared with the coating molding method, performance stability of the electrode fabricated by compression molding method is much better after 5 cycle capacitive deionization. So, the electrode fabricated by the coating molding method should be improved in aspect of performance stability.