ﺑﺮرﺳﯽ ﺟﺬب ﻧﯿﺘﺮوژن ﻣﻮﻧﻮ اﮐﺴﯿﺪ روي ﻧﺎﻧﻮ ﮐﻼﺳﺘﺮﻫﺎي Rh-Cu ﻧﺸﺎﻧﺪه ﺷﺪه ﺑﺮ ﺑﺴﺘﺮ ﻧﺎﻧﻮ ﺻﻔﺤﻪ ﮔﺮاﻓﻦ ﺑﺎ اﺳﺘﻔﺎده از ﻧﻈﺮﯾﻪ ﺗﺎﺑﻌﯽ داﻧﺴﯿﺘﻪ

Investigation of NO Adsorption on the Rh-Cu Nanoclusters Supported on Graphene Nano Sheet by Density Functional Theory

ﺳﺎﺧﺘﺎرﻫﺎي ﭘﺎﯾﺪار و ﺣﺎﻟﺖ ﻫﺎي ﻣﺨﺘﻠﻒ ﺟﺬب ﻧﺎﻧﻮﮐﻼﺳﺘﺮﻫﺎي 4-0=RhxCu4-x(x ﺑﺮ ﺑﺴﺘﺮ ﻧﺎﻧﻮ ﺻﻔﺤﻪ ﮔﺮاﻓﻦ ﺑﺎ ﺑﮑﺎرﮔﯿﺮي ﻧﻈﺮﯾﻪ ﺗﺎﺑﻌﯽ داﻧﺴﯿﺘﻪ، ﺑﺎ اﺳﺘﻔﺎده از ﺗﺎﺑﻌﯽ ﻫﯿﺒﺮﯾﺪي B3PW91 ﻣﻮرد ﻣﻄﺎﻟﻌﻪ ﻗﺮار ﮔﺮﻓﺖ. ﺳﭙﺲ ﺟﺬب ﻣﻮﻟﮑﻮل NO روي ﭘﺎﯾﺪارﺗﺮﯾﻦ ﺳﺎﺧﺘﺎرﻫﺎي ﮔﺮاﻓﻦ – ﮐﻼﺳﺘﺮ ﺑﺮرﺳﯽ ﺷﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﺟﺬب ﮐﻼﺳﺘﺮﻫﺎي ﺗﺮﮐﯿﺒﯽ Rh-Cu روي ﮔﺮاﻓﻦ ﻧﺴﺒﺖ ﺑﻪ ﮐﻼﺳﺘﺮ ﺧﺎﻟﺺ ﻣﺲ (4 Cu) از ﻧﻈﺮ اﻧﺮژي ﻣﻄﻠﻮب ﺗﺮ اﺳﺖ. در ﺣﺎﻟﯿﮑﻪ از ﺑﯿﻦ ﮐﻼﺳﺘﺮﻫﺎي ﺗﺮﮐﯿﺒﯽ، ﻓﻘﻂ ﺟﺬب ﮐﻼﺳﺘﺮ Rh3Cu روي ﮔﺮاﻓﻦ ﻧﺴﺒﺖ ﺑﻪ ﮐﻼﺳﺘﺮ ﺧﺎﻟﺺ رودﯾﻢ (2 Rh) از ﻧﻈﺮ اﻧﺮژي ﻣﻄﻠﻮب ﺗﺮ اﺳﺖ. در ﺟﺬب روي ﻫﻤﻪ ﮐﻼﺳﺘﺮﻫﺎ، ﻣﺸﺎﻫﺪه ﮔﺮدﯾﺪ ﮐﻪ ﺟﺬب از ﻃﺮف اﺗﻢ ﻧﯿﺘﺮوژن ﻣﻄﻠﻮﺑﺘﺮ از ﺟﺬب از ﻃﺮف اﺗﻢ اﮐﺴﯿﮋن ﻣﯽ ﺑﺎﺷﺪ. ﻫﻤﭽﻨﯿﻦ ﺟﺬب روي اﺗﻢ (ﻫﺎي) رودﯾﻢ ﻣﻄﻠﻮﺑﺘﺮ از ﺟﺬب روي اﺗﻢ (ﻫﺎي) ﻣﺲ اﺳﺖ. ﻣﻘﺎدﯾﺮ اﻧﺮژي ﺟﺬب NO در ﻣﺤﺪوده eV -1.62 ﺗﺎ eV -2.63 ﺑﺪﺳﺖ آﻣﺪ ﮐﻪ ﻧﺸﺎن دﻫﻨﺪه ﺑﺮﻫﻤﮑﻨﺶ ﻗﻮي ﺑﯿﻦ ﮐﻼﺳﺘﺮ و NO ﻣﯽ ﺑﺎﺷﺪ. ﺑﺎ اﻓﺰاﯾﺶ ﻣﻘﺪار Rh در ﮐﻼﺳﺘﺮ، ﻣﻘﺪار اﻧﺮژي ﺟﺬب NO اﻓﺰاﯾﺶ ﯾﺎﻓﺘﻪ اﺳﺖ و ﺑﯿﺸﺘﺮﯾﻦ ﻣﻘﺪار اﻧﺮژي ﺟﺬب ﻣﺮﺑﻮط ﺑﻪ ﮐﻼﺳﺘﺮ (4 Rh) ﻣﯽ ﺑﺎﺷﺪ. ﻃﻮل ﭘﯿﻮﻧﺪ N-O ﺑﻌﺪ از ﺟﺬب روي ﮐﻼﺳﺘﺮﻫﺎي ﺧﺎﻟﺺ Rh ﻣﯽ ﺑﺎﺷﺪ. ﻃﻮل ﭘﯿﻮﻧﺪ N-O ﺑﻌﺪ از ﺟﺬب روي ﮐﻼﺳﺘﺮﻫﺎي ﺧﺎﻟﺺ 4 Rh و Cu4 ﻧﺴﺒﺖ ﺑﻪ ﮐﻼﺳﺘﺮﻫﺎي ﺗﺮﮐﯿﺒﯽ -Rh Cu ﺑﻪ ﻣﻘﺪار ﺑﯿﺸﺘﺮي اﻓﺰاﯾﺶ ﯾﺎﻓﺘﻪ اﺳﺖ ﮐﻪ ﻧﺸﺎن ﻣﯽ دﻫﺪ ﮐﻼﺳﺘﺮﻫﺎي ﺧﺎﻟﺺ 4 Rh و 4 Cu ﻧﺴﺒﺖ ﺑﻪ ﮐﻼﺳﺘﺮﻫﺎي ﺗﺮﮐﯿﺒﯽ -Rh Cu ﺗﻤﺎﯾﻞ ﺑﯿﺸﺘﺮي ﺑﻪ ﺗﻔﮑﯿﮏ NO دارﻧﺪ. ﻫﻤﭽﻨﯿﻦ از ﺑﯿﻦ ﮐﻼﺳﺘﺮﻫﺎي ﺗﺮﮐﯿﺒﯽ، ﮐﻼﺳﺘﺮ Rh3Cu ﺗﻤﺎﯾﻞ ﺑﯿﺸﺘﺮي ﺑﻪ ﺗﻔﮑﯿﮏ NO دارد. ﺑﺎر ﻣﻨﻔﯽ NBO روي ﻣﻮﻟﮑﻮل NO ﺑﻌﺪ از ﺟﺬب روي ﮐﻼﺳﺘﺮﻫﺎ ﮐﻪ ﻧﺸﺎن دﻫﻨﺪه اﻧﺘﻘﺎل اﻟﮑﺘﺮون از ﮐﻼﺳﺘﺮ ﺑﻪ اورﺑﯿﺘﺎﻟﻬﺎي*2π ﻣﻮﻟﮑﻮل NO اﺳﺖ ﻧﯿﺰ ﺗﺎﯾﯿﺪ ﮐﻨﻨﺪه اﻓﺰاﯾﺶ اﺣﺘﻤﺎل ﺗﻔﮑﯿﮏ ﭘﯿﻮﻧﺪN-O ﻣﯽ ﺑﺎﺷﺪ.

The stable structures and different adsorption modes of RhxCu4-x(x=0-4) nanoclusters on the graphene nano sheet were studied by DFT using B3PW91 functional. Then, the adsorption of NO on the most stable structure of Graphene-Cluster was investigated. The results showed that adsorption of bimetallic Rh-Cu clusters on the graphene nano sheet was energetically more favored compared to the pure Cu4 cluster. Among bimetallic clusters, adsorption of Rh3Cu on the graphene nano sheet was energetically more favored compared to the pure Rh4 cluster. For all the studied adsorption modes of NO on the clusters, it was observed that adsorption from the nitrogen end was more favored than adsorption from the oxygen end. Also. Adsorption of NO on Rh atom(s) was more favored than adsorption on Cu atom(s). Adsorption energies of NO were obtained in the -1.62 eV to - 2.63 eV range indicating the strong interaction between NO and cluster. With increasing the amount of Rh in the cluster, the adsorption energy of NO increased in a regular trend and the maximum adsorption energy was observed for Rh4 cluster. The N-O bond length was more increased after adsorption on the pure Rh4 and Cu4 clusters compared to the bimetallic Rh-Cu clusters indicating that N-O dissociation was more likely to happen on the pure Rh4 and Cu4 clusters. Rh3Cu cluster had more tendency for N-O dissociation compared to the other bimetallic clusters. The observed negative NBO charge on NO after adsorption on the clusters indicated that electron transfer happened from the clusters to the 2π* orbital of NO which confirmed the possibility of N-O dissociation.