Speaker
Description
Selective hydrogen release from liquid organic hydrogen carriers (LOHCs) under mild conditions remains a major challenge. Here, we demonstrate that atomically precise Cu$_x$Pd$_y$ pentamer clusters supported on ZrO$_2$ enable efficient low-temperature dehydrogenation of cyclohexene with highly selective H$_2$ production. Among the investigated compositions, Pd$_5$ exhibits the highest benzene and H$_2$ formation rates, followed by Cu$_2$Pd$_3$ and Cu$_3$Pd$_2$, while Cu$_5$ is inactive. Remarkably, all active clusters completely suppress combustion, with no detectable CO$_2$ formation.
Combining catalytic measurements with in situ XPS, in situ GIWAXS, and DFT calculations reveals that catalytic performance is governed by the interplay between cluster composition, fluxional electronic structure, metal–oxygen interactions, and the reaction environment. Oxygen promotes C–H activation through oxygenated cluster ensembles while, under oxygen-deficient conditions, enabling H$_2$ to remain the dominant hydrogen-containing product. DFT calculations show that local O/OH motifs stabilize cyclohexene adsorption configurations favorable for C–H activation without excessive binding, consistent with the experimentally observed H$_2$ selectivity exceeding 99% at reduced temperatures.
These results reveal an oxygen-controlled dehydrogenation regime that challenges the conventional view of oxidative dehydrogenation as predominantly water-forming and provide a molecular-level framework for designing cluster catalysts for selective hydrogen release in LOHC-related processes.