Revealing the multi-bonding state between hydrogen and graphene-supported Ti clusters

TL;DR

This study investigates the complex bonding mechanisms of hydrogen on graphene-supported titanium clusters, revealing multiple bond types and the influence of cluster charge states through experimental and theoretical methods.

Contribution

It provides a detailed analysis of hydrogen bonding types on Ti clusters supported on graphene, clarifying the roles of ionic character and charge state in adsorption behavior.

Findings

Three hydrogen desorption peaks observed experimentally.

Identification of two ionic bond types and physisorption.

Charge state of Ti clusters determines hydrogen bonding mode.

Abstract

Hydrogen adsorption on graphene-supported metal clusters has brought much controversy due to the complex nature of the bonding between hydrogen and metal clusters. The bond types of hydrogen and graphene-supported Ti clusters are experimentally and theoretically investigated. Transmission electron microscopy shows that Ti clusters of nanometer-size are formed on graphene. Thermal desorption spectroscopy captures three hydrogen desorption peaks from hydrogenated graphene-supported Ti clusters. First principle calculations also found three types of interaction: Two types of bonds with different partial ionic character and physisorption. The physical origin for this rests on the charge state of the Ti clusters: when Ti clusters are neutral, H2 is dissociated, and H forms bonds with the Ti cluster. On the other hand, H2 is adsorbed in molecular form on positively charged Ti clusters, resulting in physisorption. Thus, this work clarifies the bonding mechanisms of hydrogen on graphene-supported Ti clusters.