Abstract
Water and its interactions with metals are closely bound up with human life, and the reactivity of metal clusters with water is of fundamental importance for the understanding of hydrogen generation. Here a prominent hydrogen evolution reaction (HER) of single water molecule on vanadium clusters Vn+ (3 ≤ n ≤ 30) is observed in the reaction of cationic vanadium clusters with water at room temperature. The combined experimental and theoretical studies reveal that the wagging vibrations of a V-OH group give rise to readily formed V-O-V intermediate states on Vn+ (n ≥ 3) clusters and allow the terminal hydrogen to interact with an adsorbed hydrogen atom, enabling hydrogen release. The presence of three metal atoms reduces the energy barrier of the rate-determining step, giving rise to an effective production of hydrogen from single water molecules. This mechanism differs from dissociative chemisorption of multiple water molecules on aluminium cluster anions, which usually proceeds by dissociative chemisorption of at least two water molecules at multiple surface sites followed by a recombination of the adsorbed hydrogen atoms.
Highlights
Water and its interactions with metals are closely bound up with human life, and the reactivity of metal clusters with water is of fundamental importance for the understanding of hydrogen generation
It is clear from this trend that Vn+ clusters readily react with water to form vanadium oxides via an adsorption–dissociation process followed by H2 release
The hydrogen evolution reaction (HER) is significant for V3+, V5+ and V9+, processes that point to the H2 release mechanism from such transition metal cluster cations
Summary
Water and its interactions with metals are closely bound up with human life, and the reactivity of metal clusters with water is of fundamental importance for the understanding of hydrogen generation. Hydrogen elimination from Albased hydrates, e.g., [Al, 20H2O]+, were proposed in previous studies[15,16,17], where the proton transfer in the water cluster network enables a migrated proton to recombine with a hydridic H at the AlIII cation, and a joint experimental and theoretical study illustrated the potential application of pure aluminium cluster anions for effective production of H2 from water[18] In these experiments, active sites on the surface of the aluminium clusters, typically Al16−, Al17−, and Al18−, produced hydrogen from contact with water at room temperature. The composition of the reaction products were measured with a homemade reflection time-of-flight mass spectrum (Re-TOFMS)[47]
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