Dissociation of water on atomic oxygen-covered Rh nanoclusters supported on graphene/Ru(0001)

Yi-Cheng Huang; Hung-Yu Yen; Liang-Wei Lan; D Dutta; A Rahmah; Yu-Ling Lai; Yao-Jane Hsu; Chien-Cheng Kuo; Jeng-Han Wang; Meng-Fan Luo

doi:10.1063/5.0060529

Dissociation of water on atomic oxygen-covered Rh nanoclusters supported on graphene/Ru(0001)

J Chem Phys. 2021 Aug 21;155(7):074701. doi: 10.1063/5.0060529.

Authors

Affiliations

¹ Department of Physics, National Central University, No. 300 Jhongda Road, Jhongli 32054, Taiwan.
² Department of Chemistry, National Taiwan Normal University, No. 88, Sec. 4, Ting-Zhou Road, Taipei, Taiwan.
³ Department of Physics, National Sun Yat-sen University, 70 Lienhai Road, Kaohsiung 80424, Taiwan.
⁴ National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan.

PMID: 34418937
DOI: 10.1063/5.0060529

Abstract

We studied the dissociation of water (H₂O*, with * denoting adspecies) on atomic oxygen (O*)-covered Rh nanoclusters (Rh_O^* ) supported on a graphene film grown on a Ru(0001) surface [G/Ru(0001)] under ultrahigh-vacuum conditions and with varied surface-probe techniques and calculations based on density-functional theory. The graphene had a single rotational domain; its lattice expanded by about 5.7% to match the Ru substrate structurally better. The Rh clusters were grown by depositing Rh vapors onto G/Ru(0001); they had an fcc phase and grew in (111) orientation. Water adsorbed on the Rh clusters was dissociated exclusively in the presence of O*, like that on a Rh(111) single-crystal surface. Contrary to the case on Rh(111)_O^* , excess O* (even at a saturation level) on small Rh_O^* clusters (diameter of 30-34 Å) continued to promote, instead of inhibiting, the dissociation of water; the produced hydroxyl (OH*) increased generally with the concentration of O* on the clusters. The difference results from more reactive O* on the Rh_O^* clusters. O* on Rh_O^* clusters activated the dissociation via both the formation of hydrogen bonds with H₂O* and abstraction of H directly from H₂O*, whereas O* on Rh(111)_O^* assisted the dissociation largely via the formation of hydrogen bonds, which was readily obstructed with an increased O* coverage. As the disproportionation (2 OH* → H₂O* + O*) is endothermic on the Rh_O^* clusters but exothermic on Rh(111)_O^* , OH* produced on Rh_O^* clusters showed a thermal stability superior to that on the Rh(111)_O^* surface-thermally stable up to 400 K.