The rational design of single metal atoms anchored on non-metallic surfaces could lead to the discovery of cost-effective catalysts that have high activity and product selectivity. In a recent joint experimental and theoretical effort, we have shown that Pd single atoms anchored on ZnO stabilize in a cationic bimetallic local environment consisting of one Pd and three Zn atoms that exhibits very high catalytic activity for generation of H2 through methanol partial oxidation (MPO) [1]. In this talk, we will compare the above findings to those obtained for singly dispersed Pt atoms on ZnO, through intertwined experimental observations and density functional theory-based calculations. Computationally, we find that methanol adsorption is favored at the surface Zn site whereas oxygen prefers to adsorb at the Pt-Zn site. The adsorption of reaction intermediates CO, CO2, and H2 are favored at the Pt site, whereas H2O prefers to sit at the Zn site. Moreover, along the reaction pathways for methanol dehydrogenation, we illustrate that the O-H bond scission from methanol is slightly endothermic (ΔE= +90 meV). The resultant methoxy then preferentially adsorbs at the Pt-Zn site, at which the methoxy C-H bond can be easily activated. The dissociation of methoxy (CH3O-&gt;CH2O+H) is exothermic (ΔE=-0.20 eV) and that of formaldehyde (CH2O-&gt;CHO+H) is endothermic (ΔE=+0.46 eV). Analysis of critical energy barriers along the reaction pathways provides insights into reaction mechanisms and suggest that Pt1/ZnO is a potential single-atom catalyst for methanol oxidation. This computational prediction of high activity and selectivity of the isolated Pt1Znn bimetallic sites was confirmed by extensive experimental exploration showing that the singly dispersed bimetallic sites Pt1Znn are much more active than Pt-Zn alloy nanoparticles supported on ZnO and exhibits very high activity and selectivity for producing H2 at a temperature as 230oC or lower.

Single atom catalyst Pt1/ZnO for methanol partial oxidation: Insights into reaction mechanisms from DFT and experiments

ACS Spring 2022

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