Fabrication of La_0.8Sr_0.2CrO₃-based Perovskite Film via Flame-Assisted Vapor Deposition for H₂ Production by Reforming†

摘要

Flame-assisted vapor deposition (FAVD) has a principle similar to conventional CVD in which a film is deposited from a vapor phase. It is a simple and cost-effective technique as it is operated in an open atmosphere. The microstructure of the deposited films is controlled by varying the processing parameters. In our research, an oxide film of lanthanum chromite perovskite-based (La_0.8Sr_0.2CrO₃) material is fabricated, using the FAVD technique, on a stainless steel substrate (SS430) for an application in solid oxide fuel cells (SOFC). The precursor solution for La_0.8Sr_0.2CrO₃ film is prepared from metal nitrate compounds with a concentration in the range 0.0125 − 0.0500 M. Dense and porous films are fabricated, depending on various processing parameters such as fuel to water ratio, air pressure, flow rate of a precursor, and the distance between the spray nozzle and the substrate. The effect of various processing parameters on the microstructure and phase formation of the deposited film are investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The deposition temperature resulting from the total heat of combustion from the combination of all the deposition parameters is very important in determining the properties of the films. According to the SEM images, a small particle size on the nanometer scale is found at high deposition temperature. On the other hand, the particles are connected into a dense film at low deposition temperatures. The main phase of LaCrO₃ is found in all deposition temperatures (temp range). For hydrogen production, the methane steam reforming over the porous film of La_0.8Sr_0.2CrO₃ at 900 °C is investigated. Under specific operating conditions (low inlet H₂O/CH₄ ratio), its catalytic reactivity is comparable to metallic-based catalysts but with less inlet steam required.