Cu-doped LaNiO3 perovskite catalyst for DRM: revisiting it as a molecular-level nanocomposite

Abstract

Dry reforming of methane (DRM) was extensively studied on Cu-doped LaNiO₃ catalysts. The main findings of this work are as follows: (i) thermal switching of the catalyst phase between the parent perovskite and molecular-level nanocomposite of individual components formed in situ during DRM, (ii) reusability of the catalyst with enhanced activity, and (iii) regeneration of the catalyst phase at a lower temperature than that required for the formation of the parent perovskite. The present investigation provides an extensive analysis and understanding of the DRM reaction using Cu-doped LaNiO₃ compared to the result reported by Moradi et al., (Chin. J. Catal., 2012, 33, 797–801) and hence provides new insights into its catalytic activity. Phase-pure LaNi_1−xCu_xO₃ catalysts, specifically LaNi_0.8Cu_0.2O₃, exhibited high catalytic activity towards the DRM reaction (97% CH₄ and 99% CO₂ conversion with an H₂/CO ratio of ∼1.4–0.9). Remarkably, although the initial perovskite phase primarily decomposed into its component phases after DRM, its catalytic activity was barely affected and maintained even after 100 h. The regeneration of the initial perovskite from the disintegrated binary phases via annealing at temperatures even lower than the synthesis temperature together with the amazing retention of activity was very intriguing. The parallel activity of the pristine perovskite and its degraded binary mixtures makes it difficult to identify the actual components responsible for the DRM activity. Accordingly, we have explained the sustained activity of the degraded perovskite catalyst in the context of nanocomposite formation at the molecular level in the reforming atmosphere with the availability of Ni⁰ and NiO, as revealed by the thoroughly characterized samples in the as-prepared, aged, and regenerated forms.