When comparing alloy catalysts with different degrees of ordering, it is important to maintain surface facets to understand the effect of different arrangements of surface atoms. This is even more important when both metals are involved in the reaction steps, which is the case of Pt 3 Sn for the methanol oxidation reaction (MOR). We have prepared 95 and 60% ordered Pt 3 Sn nanocubes with {100} facets for the MOR. We show that the Sn atoms in the 60% ordered Pt 3 Sn nanocubes can be electrochemically oxidized to Sn 4+ , whereas the Sn atoms in the 95% ordered Pt 3 Sn nanocubes are more resistant to oxidation. The Sn 4+ in the disordered catalysts makes them more active than the ordered catalysts. At low overpotentials, the electrochemically formed Sn 4+ in the 60% ordered Pt 3 Sn nanocubes bind OH, oxidizing the CO intermediate adsorbed on Pt more efficiently. At high overpotentials, Sn 4+ prevents the passivation of the Pt sites due to adsorption of OH. These effects lead to a 5.6 times higher activity of the 60% ordered nanocubes compared to the 95% ordered nanocubes. These results illustrate the importance in catalyst design of controlling the environment and especially the atoms neighboring Pt for intermetallic Pt−M electrocatalysts.

Pd or Pt alloyed with a secondary metal are the typical catalysts at the anode for the direct oxidation of methanol. The secondary metal is employed to diminish deactivation commonly ascribed to CO poisoning. Here we investigate the origin of the improved performance of Au–Pd core–shell and alloy nanocrystals as electrocatalysts for the methanol oxidation reaction (MOR), relative to Pd alone. Monodisperse Au–Pd core–shell nanocrystals were synthesized using H2 as a mild reducing agent followed by annealing under a 5% H2 atmosphere to produce the Au–Pd alloys. The nanocrystals were characterized using high-resolution electron microscopy to confirm their structures. The core–shell and alloy nanocrystals showed an improvement in specific activity with respect to pure Pd nanocrystals. Importantly, the stability was also improved by the inclusion of Au for both nanocrystals, being 2.7× higher for the alloy than for the core–shell after 30 min, while the activity is completely lost for the Pd nanocrystals within 10 min. We show that there is no evidence of CO formation for any of the Pd-based catalysts in an alkaline environment. The origin of the improvement in terms of both activity and stability results from positive shifts in the PdO formation/reduction potential caused by the presence of Au, which results in more Pd sites available for the MOR.

Organometallic coordination compounds in general and metallocenes in particular are convenient precursors for the synthesis of metal nanoparticles through thermal decomposition. The strength of the interaction between the metal ion and its ligands determines the conditions under which decomposition occurs, most importantly the range of temperatures and pressures at which a given compound is useful as a precursor. We show that a comprehensive analysis of all individual contributions to the ligand metal interactions that establishes the nature of the interaction can be used to select compounds that are tuned to a specific dissociation energy with advantageous properties under experimental conditions. To this end, we apply the Morokuma-Ziegler-Energy Decomposition Analysis (MZ-EDA) to a series of ferrocene analogues using high-level density functional theory (DFT). We find that asymmetrically substituted ferrocene derivatives are unlikely to be useful as precursors because of the large energy required to remove the second cyclopentadienyl-derivative from the central iron atom. However, we are able to establish that symmetrically substituted chloroferrocenes exhibit a wide range of relatively low bond dissociation energies for both dissociation steps and are hence good candidates for the synthesis of highly mono-disperse iron nanoparticles.

The electrochemical formation of oxide on metallic surfaces often changes their electrocatalytic performance. In this work, we have studied this effect on the methanol oxidation reaction by systematically controlling the PdO formation/reduction potential using Au−Pd core‐shell nanocrystals with different Pd shell thicknesses. AuPd0.4 core‐shell nanocrystals have a 150 mV positive shift in the PdO reduction potential with respect to Pd nanocrystals and 2.9 and 8.8 times higher charge density in the anodic and cathodic scan of cyclic voltammetry respectively. The origin of the higher activity comes predominantly from electronic effects caused by the Au core that results in higher availability of Pd sites at more positive potentials.

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