Designing Highly Active and Stable Ni-Exsolved LaMnO3 Perovskite Catalysts for Dry Reforming of Methane via Ca Substitution

Dry reforming of methane (DRM) has increasingly incorporated perovskite-based exsolution catalysts due to their high stability and tunability, offering a promising route for effective methane and carbon dioxide conversion. This study investigates the effect of substituting La³⁺ with Ca²⁺ at the A-site of LaMn_0.8Ni_0.2O_3±δ (LMN) perovskite oxides to enhance Ni nanoparticle exsolution, and resulting catalytic activity for the DRM. The substitution of Ca facilitates Ni exsolution and modulates the catalytic properties of LMN, leading to improved methane and carbon dioxide conversions and enhanced resistance to carbon deposition. This becomes more evident through additional exsolution at 800 °C under DRM conditions, where most of the Ni is gradually exsolved from the bulk. Comprehensive characterization using ex situ/in situ XRD, SEM, TEM, ICP-OES, and EDS was performed to understand the impact of Ca substitution on the physical and chemical properties of the catalysts. Catalytic tests at 800 °C for 500 h revealed that 20% Ca-substituted LMN exhibited optimal DRM performance in terms of mass activity and turnover frequency and long-term stability with negligible carbon deposition. The comparison with conventional Ni (20 wt %)/γ-Al₂O₃ catalysts further highlights the superior durability of 20% Ca-substituted LMN, maintaining its performance over extended reaction times. Our findings demonstrate that moderate Ca substitution not only enhances Ni exsolution but also maintains the perovskite structure, offering a promising approach to maximize catalyst activity and stability for DRM applications.