Heterogeneous catalysis by singly-dispersed metal atoms on non-metallic surfaces offers great potential for maximizing the efficiency of metal atoms, and optimizing their activity and selectivity. Herein, we present results from our ab-initio density functional theory (DFT) calculations for methanol partial oxidation (MPO), an industrially important reaction for the production of H2, on Pd1/ZnO(100). To begin with we find that the Pd atom prefers to adsorb at the oxygen vacancy site i.e. the anion vacancy is responsible for stabilizing singly-dispersed Pd atom on ZnO(100). We discuss the adsorption characteristics of a set of gas molecules (CH3OH, O2, CO, CO2, H2O, H2), and the potential energy profile including activation barriers for the reaction processes associated with MPO on Pd1/ZnO(100), and compare them with those on Pd16Zn16 nanoparticle and pristine ZnO(100). We find that the singly dispersed Pd sites offer a high activity towards the formation of CO2 and H2 over that of CO and H2O. We trace this reactivity to the electronic structure of the single Pd site as modified by its local environment which in turn facilitates a strong binding of CO to the Pd site, thereby increasing the CO desorption barrier and stabilizing O2 on ZnO(100), which is essential for further oxidation steps. With activation energy barriers and pre-exponential factors calculated from DFT, for a large set of reaction intermediates, we perform kinetic Monte Carlo simulations to determine the turn over frequencies and rate limiting steps in the formation of CO2 and H2 on Pd1/ZnO(100), under ambient conditions. Work supported in part by DOE grant DE-FG02-07ER15842

Methanol partial oxidation catalyzed by singly-dispersed Pd on ZnO(100)

253rd National Meeting (2017)

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