Inhibition of coking and CO poisoning of Pt catalysts by the formation of Au/Pt bimetallic surfaces

The surface of Pt catalysts can be deactivated or poisoned during catalytic and electrocatalytic processes because of its strong bonding to hydrocarbon intermediates and carbon monoxide (CO). In the current work we have evaluated whether the formation of an Au/Pt bimetallic surface alloy would improve the resistance to coking and CO poisoning, using a combination of density functional theory (DFT) modeling and temperature-programmed desorption (TPD) experiments. The DFT results indicated that the binding energies of adsorbates, such as atomic hydrogen and oxygen, were much weaker on Au/Pt surfaces in comparison to Pt. The CO desorption TPD revealed that the Au/Pt surface bonded CO more weakly than Pt, indicating that modifying Pt with Au could potentially help reduce CO poisoning. In addition, the decomposition and dehydrogenation of cyclohexene were used as probe reactions to compare the extent of carbon deposition on the Pt and Au–Pt surfaces. TPD results showed that the presence of Au on Pt promoted the selective dehydrogenation of cyclohexene to benzene. In addition, Auger electron spectroscopy (AES) measurements revealed that the Au/Pt bimetallic surfaces inhibited carbon deposition on the surface, suggesting that the Au/Pt bimetallic alloy could be potentially resistant to coking.

Results from DFT modeling indicate that the formation of Au–Pt surface alloy reduces the biding energy of adsorbates, which should lead to a reduction in the extent of coke formation and CO poisoning on Pt. The reduction of coke formation is verified experimentally based on the decomposition of cyclohexene; the weakening of CO adsorption is confirmed based on the desorption temperatures of CO from Pt and Au–Pt surfaces.Figure optionsDownload high-quality image (121 K)Download as PowerPoint slide