(322d) Exploring Interfacial Reaction Pathways Involved in Dry Reforming of Methane on Oxide Supported Ni Catalysts

Mitigating greenhouse gas emissions is a critical global challenge, and dry reforming of methane (DRM) offers a promising pathway for the simultaneous conversion of CH₄ and CO₂ into value-added syngas. However, catalyst deactivation due to carbon deposition at high operating temperatures remains a major bottleneck. Ni metal particles supported on reducible oxides such as CeO₂ have demonstrated strong potential as DRM catalysts, benefiting from the ability of Ni to activate CH₄ and the capacity of CeO₂ to mitigate coking via lattice oxygen transport to Ni sites. A detailed mechanistic understanding of the interfacial events and the influence of interfacial intermediates on CH₄/CO₂ activation remains limited.

Using Density Functional Theory (DFT) calculations (catalyst model - Ni_n/CeO₂) along with microkinetic modeling (MKM), we elucidate the role of oxide-metal interface in promoting interfacial reaction rates and stabilizing reaction intermediates. DFT calculations reveal a 1.5 eV barrier for O-migration across the oxide support. Interestingly, CO₃^2- like species significantly lower this barrier, enabling near-barrierless O-migration. Degree of rate control analysis on our multi-site MKM identifies O-transport across the interface, from the support to the metal, as one of the rate-determining steps. We hypothesize that the enhanced stability of CO₃²⁻ species proximal to metal-oxide interfaces could similarly result in facile interfacial O-transport, thereby mitigating coke formation and potentially altering the rate-determining steps. Oxygenate interfacial species also participate in CH₄ activation, decreasing the reaction energy required for the first C–H bond cleavage by at least 0.5 eV, unveiling alternative CH₄ activation pathways. The mechanistic relevance and kinetic dominance of these pathways is further confirmed by a DFT-based MKM analysis. Altogether, this work offers mechanistic insights into interfacial events occurring in DRM, advancing the understanding of oxide–metal interfaces in catalytic systems.