Obtenção e caracterização de cermetos Ni-BCZY para uso como ânodo de células a combustível.

Abstract

The fuel cells are defined as devices with the ability to convert electrochemical energy into electrical energy and heat, having water as the main by-product. Several types and variations of fuel cells are studied and already have practical applications, including solid oxide fuel cells, characterized by the use of ceramic material as electrolyte. One of the main obstacles for its use is the high temperature, remaining between 600°C and 1000°C, reducing its useful life and the range of applications. The progress of the studies led to the use of oxides with proton type conduction, opening the way to reduce the temperature range for cell use, reaching temperatures between 400°C and 700°C. These cells came to be known as protonic ceramic fuel cells, and it uses materials with perovskite-like structures. Therefore, there are compounds such as Ba(Ce, Zr, Y)O3 (BCZY), which has characteristics such as good proton conductivity and good chemical stability. When used as anodes, nickel-based cermets (Ni) are widely studied, thus joining this metal with the material used in the electrolyte, such as BCZY. This work studied the use of Ni-BCZY cermet for use in protonic ceramic fuel cell anodes. The BCZY, with Ba(Ce0,2Zr0,7Y0,1)O3-δ composition, was obtained through synthesis based on the Pechini method. The formation of cermet was performed by a mechanical mixture in eccentric vibrating mill, between NiO and BCZY, in weight ratios of 40/60, 50/50 and 60/40 respectively. The electrical properties were evaluated by impedance spectroscopy, after heat treatment to reduce NiO to Ni. The cermets was observed in the three proportions studied, with characteristics such as the percentage of porosity and electrical conductivity suitable for each proportion. The compositions Ni-BCZY 60/40 and Ni-BCZY 50/50 showed conductivity values above 0.1 S/cm and activation energies of 0.02 eV/atom, demonstrating the feasibility of using as anode. With the results presented, the Ni-BCZY 50/50 composition was used to form a symmetric cell, it having BCY as an electrolyte, thus verifying the formation of this configuration and the electrical behavior of this type of cell.