Research paperElectrical properties of TiO2-pillared bidimensional manganese oxides

•The formation of TiO2 in the interlayered region of a birnessite was achieved by a simple process.•The electrical properties of the materials changed through the entire process.•The electrical properties correlated well with the other physicochemical properties.

This work consists on modifying a layered manganese oxide material with a tytanyl acylate complex through an ion exchange reaction and performing a pillaring process by thermal treatment to induce the formation of titanium oxide nanoparticles in the interlayered space. Atomic absorption spectroscopy (AAS) evidenced a 6.54 w% Ti in the material. The XRD patterns showed the typical basal spacing of the birnessite type structure, not significant changes occurred after pillaring. The layer structure is maintained at 175 °C, and above this temperature causes the formation of pyrolusite, hausmannite and bixbyite in accordance with thermal events shown in the TGA and DSC analysis. SEM shows the plate like morphology characteristic of this type of materials. The pillared material had more compact morphology. The N2 adsorption-desorption isotherm was type II and shows variation in the hysteresis loops. The BET area increases from 28 m2/g to 108 m2/g, the micropore area increases from 0.88 m2/g to 16.85 m2/g, the mesopore size decrease (from 163 Å to 136 Å) and the micropore size distribution shows a bimodal behavior which indicates a successful pillaring process. The impedance spectroscopy results of the pristine material showed electron transport in bulk and grain boundaries (high frequencies) plus ionic conduction (low frequencies), after pillarization process the electric behavior of the material was mainly due to electrical conduction since the diffusion process associated with ionic conduction was no longer observed. The AC conductivity at high frequency for the pillarized material was three times the conductivity of the raw material. The DC conductivity was thermally activated and it was higher for the pillared material than for the pristine material. There was also experimental evidence of thermally activated dielectric relaxation.

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