Indexed on: 13 Jul '18Published on: 05 Jul '18Published in: Journal of Physical Chemistry C
A systematic density functional theory (DFT) investigation has been performed to understand adsorption phenomenon as well as the mechanism of hydrogen molecule dissociation to form metal hydride, catalyzed by bare and activated carbon-supported small rhodium clusters. H–H bond length of hydrogen molecule adsorbed on activated carbon-supported rhodium cluster is found to be higher. Five- as well as six-member rings of the activated carbon act as the support for hydrogen-adsorbed rhodium clusters. Rhodium cluster linked with five-member ring of activated carbon has the enhanced ability to activate hydrogen molecule. DFT-evaluated transition states show lower activation energies in the dissociation of hydrogen molecule catalyzed by activated carbon-supported rhodium clusters, whereas dissociation of hydrogen molecule catalyzed by Rhn, supported on activated carbon, follows two pathways. First, hydrogen atoms stay on Rhn after dissociation, and in the second, hydrogen is dislodged from Rhn to carbon of the activated carbon, which is called spillover. The first pathway is observed to be more favorable in comparison to the second pathway. However, the supported Rh4 exhibits equal feasibility for both the pathways.