Pt nanoparticles breathe and reversibly detach from Al2O3 in hydrogen

The dynamic behavior of supported metal nanoparticles under reaction conditions is a key factor in their catalytic performance. Pt nanoparticles are particularly susceptible to structural relaxation induced by adsorbed CO and H2. In a hydrogenated state, theoretical models predict the reshaping of Pt nanoparticles, but also their shift away from the support. Here, we examine the dynamic structural behavior of well-dispersed 1-3 nm diameter Pt nanoparticles under hydrogenation conditions. Using time-resolved X-ray diffraction and pair distribution function analysis allied to a modulated excitation approach, we provide experimental evidence of the simultaneous “breathing” of the Pt nanoparticles and their detachment from the Al2O3 support under H2. These effects appear size-dependent, reversible, and occur in both gas-phase (150 °C) and liquid-phase (cyclohexane, 70 °C) conditions. Achieving direct evidence of the behavior of supported metal nanoparticles towards structural deformation in reactive chemical environments is a groundbreaking step towards precise structural control of catalysts under reaction conditions. The dynamic behavior of supported metal nanoparticles under reaction conditions plays a crucial role in determining their catalytic performance. Here, time-resolved XRD, PDF, and modulation techniques provide direct evidence of hydrogen-induced breathing and detachment of Pt nanoparticles from an alumina support, uncovering reversible, size-dependent dynamics in both gas and liquid phases.