Perpustakaan Digital ITB

Recent research on materials for capacitivedeionization (CDI) has shown that intercalation materials havesalt removal capacities (>40 mg g?1) much higher than those ofcarbon materials (?15 mg g?1). However, little work has beendone to elucidate the relationship between the microstructure ofan intercalation material and its desalination performance.Herein, we report the desalination performances of variouscrystalline forms of MnO2in a hybrid CDI setup without the useof ion-exchange membranes. MnO2materials used in ourexperiments were either poorly crystalline or crystalline formsof 1D hollandite?-MnO2, 2D birnessite?-MnO2, and 3D spinel?-MnO2. X-ray photoelectron spectroscopy performed onelectrochemically cycled MnO2showed redox changes associatedwith intercalation processes in crystalline MnO2, whereas poorlycrystalline MnO2showed no such changes. It was further shown that surface adsorption is dominant in poorly crystalline MnO2and that poorly crystalline forms of?-MnO2and?-MnO2exhibited the highest salt removal capacities of 0.17 and 0.16 mmolg?1(9.93 and 9.35 mg g?1), respectively. These performances are comparable to state-of-the-art carbon materials and areremarkable considering the low surface areas (<400 m2g?1) of MnO2materials.