Pd-supporting LaCoO₃ catalyst with structured configuration for water gas shift reaction

The purpose of this study was to develop a structured perovskite-type oxide catalyst for the water gas shift (WGS) reaction, which could make lattice oxygen mobile at a low external heat energy by preparing it as a thin catalyst layer on a metal plate. The thickness of the formed LaCoO₃ layer was about 20 μm, which was confirmed by FE-SEM and EDX analysis. For enhancing its WGS reaction performance, a palladium (Pd) component was supported on the structured catalyst using various Pd precursors. When using a PdCl₂ aqueous solution which was prepared by filtration of the PdCl₂ slurry (the filtration liquid), the Pd-supporting LaCoO₃ structured catalyst showed a high and stable activity. The reason for such an enhanced activity was that the supported Pd was in a highly dispersed state, which was derived from the electrostatic interaction between [PdCl₃(H ₂O)]^- as the anionic charged precursor in the filtration liquid and the oppositely charged LaCoO₃ support surface confirmed by a UV-vis measurement. In order to remove the remaining chloride ligand from the Pd-supporting LaCoO₃ catalyst surface, a washing treatment was performed by immersing the as-made catalyst in water, NH₃ (aq) or NaOH (aq) at pH 11.5 for 30 min. Consequently, these washing processes were effective for eliminating the remaining chloride ion from the catalyst surface and improving the shift activity of the catalyst. The catalyst washed using NH₃ (aq) showed the highest activity among these catalysts.