Pulse-Width-Dependent Laser-Induced Nonequilibrium Microstructural Evolution of Pd Nanocubes for Ethanol Electrooxidation.

Abstract

Laser irradiation enables a noncontact pathway for the nonequilibrium structural modification of nanomaterials. Here, the laser irradiation-induced microstructural evolution of Pd nanocubes (Pd NCs) is investigated by combining theoretical simulations and experimental validation. Coupled finite element method-molecular dynamics (FEM-MD) simulations reveal the distinct nonequilibrium microstructural evolution pathways of Pd NCs under nanosecond (ns) and femtosecond (fs) laser irradiation. Although both processes involve rapid heating and cooling, ns laser irradiation follows a thermally extended melting-annealing pathway that yields heterocrystalline structures, whereas fs laser irradiation induces rapid heating-flash freezing pathway that produces amorphous structures. Additionally, a microstructural disorder descriptor (w*) is introduced to quantitatively correlate laser-induced microstructure with ethanol electrooxidation activity. The results reveal that ethanol electrooxidation activity initially increases and then decreases with increasing w* and exhibits a volcano-type dependence on laser irradiance. Notably, the laser-induced heterocrystalline Pd nanospheres (HC-Pd NSs) achieve the highest mass activity of 3.98 A mg-1. Density functional theory (DFT) calculations reveal the predominant role of Pd NC microstructure in modulating the electronic structure and intermediate adsorption. This work provides a mechanistic basis for pulse-width-dependent laser-induced nonequilibrium microstructure engineering in nanomaterials and establishes a laser parameters-microstructure-activity framework for guiding the performance optimization of nanocatalysts.

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