Theoretical Studies on the Synergetic Effects of Au–Pd Bimetallic Catalysts in the Selective Oxidation of Methanol

Abstract

The selective oxidation of methanol to formaldehyde with molecular O 2 on Au-Pd alloy surfaces has been studied by using density functional theory (DFT). We show that the existence of Pd remarkably improves the adsorption and activation of O 2 on Au-Pd surfaces. In particular, the second-neighbor Pd monomer pair (Pd-SNMP) surrounded by gold atoms can provide unique active sites for the co-adsorption of O 2 …CH 3 OH, thus facilitating the activation of O 2 via a hydroperoxyl radical ( * OOH). With the involvement of * OOH and its decomposed fragments ( * O and * OH), the oxidative dehydrogenation of methanol to formaldehyde is facilely achieved on bimetallic Au-Pd surfaces, the barriers of which are calculated to be 0.02-0.45 eV on Au 2 Pd/(111) and AuPd/(100) surfaces.Importantly, we find that the unusual activation of O 2 via an OOH-pathway instead of direct dissociation on Au-Pd catalysts is mainly responsible for the enhanced activity and selectivity in the selective oxidation of alcohols. This hydroperoxyl-based mechanism reveals the intrinsic synergy of Au-Pd bimetallic catalysts in the selective oxidation of alcohols and may provide insights for designing better bimetallic catalysts.

The promotional role of water in heterogeneous catalysis: mechanism insights from computational modeling

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AuPd‐Fe3O4 Nanoparticle‐Catalyzed Synthesis of Furan‐2,5‐dimethylcarboxylate from 5‐Hydroxymethylfurfural under Mild Conditions

“…The synergistic effect of the AuPd bimetallic surface for the O 2 activation compared with the Au surface alone has been well documented . Han and Mullins and Li and co‐workers reported that the propensity of O 2 adsorption is correlated with the coverage of isolated Pd active sites by Au atoms. If isolated Pd sites surrounded by Au are neighbored, O 2 activation is promoted.…”

Nanostructured Pd-Based Electrocatalyst and Membrane Electrode Assembly Behavior in a Passive Direct Glycerol Fuel Cell

“…The addition of Au into Pd is believed to greatly enhance the catalytic activity, stability, and selectivity, as well as provide resistance to poisoning. Au has a higher electronegativity, and thus, the charge is transferred from Pd to Au, making Au as a promoter that plays the role of isolating the Pd monomer site, thereby preventing the occurrence adsorption of CO by promoting further reaction mechanism on another pathway [11, 12]. Furthermore, the alloying of these two metals leads to the gain of s and p electrons and the loss of d electrons for Au, whereas Pd loses s and p electrons but gains d electrons [13].…”