Nanotechnology and nanomaterials

Surface Chemistry of Nanoscaled Spinels
Voronova A.S.1, Ivanenko I.M.1
1 Department of Inorganic Substances, Water Purification and General Chemical Technology, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”. Prosp. Peremohy, 37, Kyiv-03056, Ukraine. 
E-mail: anastasiavoronova666@gmail.com 

Spinel-type mixed transition metal oxides are widely used as catalysts in a variety of sensory systems and energy converting devices. As it is known, the solid-aqueous interfacial chemistry of mixed oxides significantly affects their electro-kinetic response, adsorption, catalytic and physical properties. Establishing the dependence of the exchange capacity on the solution pH, as well as finding the working pH range for spinel-type oxide is an important step in the researching process.

a

b

Fig. 1. The pH-potentiometric titrations curves (a); the moles number of surface deprotonated (right) and protonated (left) groups in the function of pH (b).	

In the research process, Ni-, Co-spinel with general formula NiCo2O4 was synthesized by co-precipitation method, and its surface chemistry was investigated by pH-potentiometric titration. The experimental results are presented in Fig. 1.
As can be seen, the obtained sample exhibits a low cation- and anion-exchange capacity, which is generally characteristic of spinel-type materials. The point of zero charge (PZC) is observed at pH 6.98, and the working pH range is from 6 to 10.