Impact of Pd:Pt ratio of Pd/Pt bimetallic catalyst on CH4 oxidation

Bimetallic Pd/Pt catalysts have recently attracted considerable attention in controlling emission control of methane. Here, we show the impact of Pd/Pt ratio (1:0, 9:1, 3:1, 1:1, 1:3, 1:9, 0:1) on the catalytic methane oxidation under simulated exhaust environments from the CH 4 -rich to -lean feed. Under dry feed conditions, the CH 4 oxidation activity was linear to the Pd:Pt ratio, where the Pd-only (1:0) exhibited the best performance. However, under wet feed conditions containing 5% of water vapor, bimetallic Pd/Pt catalysts having a small fraction of Pt showed superior overall activities in a wide range of reaction environments. The interaction of Pd-Pt, forming active PdO-Pt pair sites, was confirmed by a series of analysis such as STEM-EDS, XPS and H 2 -TPR. The evidence by DFT calculations relates the distinct properties of bimetallic Pd/Pt sites to (i) stable CH 4 adsorption, (ii) facile C–H bond cleavage and (iii) weaker adsorption of water on Pt site. • Comprehensive CH 4 oxidations were examined with various Pd:Pt ratio. • Small substitution of Pt to Pd-only remarkably enhances catalytic performance. • The Pd-Pt bimetallic catalyst forms active PdO-Pt pair site and metallic Pt site. • PdO-Pt site exhibits strong adsorption to methane and facile C-H bond cleavage. • Facile H 2 O desorption on PtPd catalyst also enhances H 2 O resistance.