Edge-Selective Growth of MCp2 (M = Fe, Co, and Ni) Precursors on Pt Nanoparticles in Atomic Layer Deposition: A Combined Theoretical and Experimental Study

摘要

Recent experiments about the selective coating of transition-metal oxide on Pt nanoparticles have aroused great interest in molecular catalysis for the promotion of both activity and stability. In this work, first-principles calculations combined with microkinetic methods are employed to shed to light on the edge-selective growth mechanism of 3d-transition metal oxide on Pt nanoparticles in atomic layer deposition (ALD) from the metal cyclopentadienyl precursors (MCp2, M = Fe, Co, and Ni). The MCp2 decomposition on the surface of Pt nanoparticles exhibits robust preferential growth, following the order of edge (100) (111), which indicates that edges are naturally selected to be covered and the (111) facets could survive toward the MCp2 precursors. The preferred deposition on the edge site is attributed to a more favorable splitting path for the precursors. On the other hand, competing reactions make the overall reaction rates of MCp2 precursors on edge sites follow the order of NiCp2 FeCp2 CoCp2. Moreover, the reaction rate analysis indicates that the edge selectivity of MCp2 on Pt nanoparticles is temperature dependent, and a high temperature will suppress the selectivity between different sites. FeCp2 could maintain high selectivity in a wide temperature range among the three precursors. The theoretical predictions about the edge-selective growth of MCp2 are confirmed by the Fourier transform infrared measurements of CO signals on successive ALD-coated Pt nanoparticles. The combination of theoretical and experimental study demonstrates the robust edge-selective growth of MCp2 on Pt nanoparticles, which may open up a new avenue for the design of metal-oxide composite catalyst with specific site passivation.