Corneliu Doroftei

By Corneliu Doroftei

Until recently, for reducing the environment pollution, the combustion catalysts based on noble metals was considered the most active, practically irreplaceable. Their high cost, high thermal instability, high sensitivity to deactivation and to the attack of some harmful elements or compounds determine the intensification of studies to replace them with new cheaper and stable catalysts. Numerous experimental data from literature indicate that the semiconductive oxidic compounds can compete with combustion catalysts based on noble metals from catalytic activity standpoint. Recent studies led to the realization of remarkable catalytic activity at moderate (350–600°C) and high (over 600°C) temperatures at some oxidic perovskite compounds, which contain transition metals. In this study are presented a series of nanostructured oxidic compounds with perovskite structure, based on transition metals and synthesized by the precursor method of self-combustion, using polyvinyl alcohol as colloidal medium, for catalytic combustion of some volatile organic compounds at low (50–350°C) and moderate temperatures. The catalytic activity of the perovskite compounds in the total oxidation reactions of the gases is largely determined by the amount of weakly bound surface oxygen species which in turn depends on the presence of oxygen vacancies.

Part of the book: Nanostructures in Energy Generation, Transmission and Storage

By Corneliu Doroftei and Liviu Leontie

Nanostructured oxide semiconductor compounds have gained a big importance, in basic and mostly in applicative researches, due to their unique properties, and their increased potential of utilization as sensors in various electronic and optoelectronic devices. The development of devices based on semiconductor materials as gas sensors has been visible during the recent years, due to their low manufacturing cost. Because the basic materials and the manufacturing processes are critical for gas sensors high performance, they need to be studied and capitalized in practice. Among the new technologies, the production of nanocrystalline materials and hybrid structures offer huge opportunities to improve sensitivity, selectivity and response time, as a consequence of the intensification of gas-sensor interaction. In this study, a series of nanostructured oxide semiconductor compounds with a spinel-type structure and perovskite, respectively, based on transition metals and synthesized by the sol-gel self-combustion method, with possible applications for resistive gas sensors, are presented.

Part of the book: New Uses of Micro and Nanomaterials