Synergistic effect between Pt and Ir in PtIr/TiO2 bimetallic catalysts boosting methane combustion activity
Highly efficient catalysts for methane combustion have long been pursued due to the intrinsic inertness of CH 4 . In this work, bimetallic PtIr/TiO 2 catalysts with varying Pt:Ir ratios were synthesized to modulate the electronic structures of the metals, thereby achieving bimetallic synergy to enhance CH 4 combustion activity. Among the series of monometallic and bimetallic catalysts, Pt 0.5 Ir 0.5 /TiO 2 exhibited the highest activity, achieving complete CH 4 conversion (T 100 ) at 370°C after activation during the first reaction cycle. Combined experimental and computational studies elucidated that the incorporation of Ir facilitated electron transfer and the formation of partially oxidized Pt δ+ (0 < δ < 2) species, which were coordinatively unsaturated and more conducive for CH 4 oxidation. The high affinity of Ir for oxygen enabled the Pt δ+ species to be stabilized under CH 4 oxidation reaction conditions, instead of being overoxidized into Pt 2+ species as in the monometallic Pt 1 /TiO 2 catalyst. Simultaneously, Ir species in the bimetallic catalyst were oxidized into Ir δ+ species during the reaction and ultimately formed the Pt δ+ -O-Ir δ+ interface to further elevate the reaction activity. Moreover, the bimetallic catalysts integrated the merits of Ir for CH 4 adsorption and Pt for intermediates conversion, synergistically boosting the reaction activity. This work provides insight into designing effective CH 4 combustion catalysts through fine-tuning the metal electronic structures.
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