Heterobimetallic Iridium-Niobia Catalyst for Efficient and Selective Methane Ammonia Reforming

A Surface OrganoMetallic Chemistry (SOMC) approach, leveraging a molecularly defined heterobimetallic niobium-iridium complex, was used to prepare a mesoporous SBA-15 silica-supported Ir-NbO_x catalyst. The resulting Ir-NbO_x/SiO₂ catalyst exhibited excellent catalytic performance in selective methane/ammonia reforming. Specifically, the Ir-NbO_x/SiO₂ catalyst showed significantly higher activity (turnover frequency 8.5 s^-1), selectivity (75%), and stability than the Ir/SiO₂ analog, whereas the NbO_x/SiO₂ counterpart was almost inactive. This contrasts with ethane/ammonia reforming via C-C cleavage, for which the bimetallic Ir-NbO_x/SiO₂ was less active than Ir/SiO₂, demonstrating tuned selectivity toward C-H activation rather than C-C cleavage due to the Ir/NbO_x synergy. Importantly, an Ir-NbO_x/SiO₂ reference catalyst, prepared by conventional impregnation/calcination/reduction steps, was found to be inactive, highlighting the value of the SOMC catalyst preparation approach using well-defined heterobimetallic precursors. These results represent a significant advance over existing catalysts due to the atomic-scale synergy between Ir and NbO_x sites, enabling access to activity and selectivity regimes inaccessible to monometallic analogs.