Exsolution-Engineered Ni-Based Titanate Perovskites for Dry Reforming of Methane: Activity-Stability Trade-Offs and Deactivation Mechanisms

Abstract Syngas production via dry reforming of methane (DRM) represents a promising route for the valorization of carbon-based molecules, CH4 and CO2, in the emerging decarbonization era. However, the harsh operating conditions required by DRM demand highly active and robust catalysts to exploit this process for hydrogen production. In this context, the rational design of thermally stable catalysts with enhanced resistance to deactivation becomes essential. Herein, we focus on elucidating the structural and morphological evolution of Ni-, Ni–Co-, and Ni–Fe-doped titanates with a perovskite framework during guest cation incorporation and subsequent exsolution. Structural, compositional, and surface modifications were investigated by XRD, SEM, EDX, XAFS, N2 physisorption, and XPS. The catalytic performance of the exsolved materials was evaluated in DRM. The Ni-doped titanate (LSTNO-H) exhibited higher catalytic activity than Ni/γ-Al2O3 for CO2 conversion, reaching 80% conversion at 708 °C compared to 715 °C under short-term tests. However, the titanates still show room for improvement in long-term activity and durability. To elucidate the mechanisms governing catalyst deactivation, DRM tests were performed under diluted conditions, enabling a comparative assessment of structural and surface changes during reaction. Under such conditions, catalyst deactivation was mainly associated with nanoparticle sintering, with partial metal oxidation potentially contributing to activity loss, while no significant carbon deposition was detected. In contrast, the benchmark Ni/γ-Al2O3 catalyst showed carbon deposition, although no measurable deactivation occurred under the investigated conditions. Overall, this study highlights the potential of exsolution-based titanates for DRM while providing insights into the deactivation behavior of exsolved Ni under the investigated conditions.