Tafreshi, SS; Roldan, A; de Leeuw, NH; (2014) Density Functional Theory Study of the Adsorption of Hydrazine on the Perfect and Defective Copper (100), (110), and (111) Surfaces. JOURNAL OF PHYSICAL CHEMISTRY C , 118 (45) 26103 - 26114. 10.1021/jp5078664.

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Abstract

We have calculated the adsorption of the reducing agent hydrazine (N2H4) on copper surfaces using density functional theory calculations with a correction for the long-range interactions (DFT-D2). We have modeled the perfect and a number of defective Cu(100), (110), and (111) surfaces, which are found in the experimentally produced structures of copper nanoparticles. We have studied adsorption of hydrazine at three types of defects in the surfaces, i.e., monatomic steps, Cu adatoms, and Cu vacancies. Several low-energy adsorption structures for hydrazine on each perfect and defective surface have been identified and compared. Our calculations reveal that hydrazine bridges surface copper atoms, with the molecule twisted from the gauche toward an eclipsed conformation, except on the adatom (100) and vacancy-containing (100) and (110) surfaces, where it adsorbs through one nitrogen atom in gauche and trans conformations, respectively. The strongest adsorption energy is found on the stepped (110) surface, where hydrazine bridges between the copper atoms on the step edge and the terrace, as it stabilizes the low-coordinated copper atoms. Our results show that, although the (110) surface contains a number of low-coordinated atoms that enhance the surface-molecule interactions, the addition of defects on the more stable (111) and (100) surfaces provides sites that enable hydrazine binding to almost the same extent. This study also confirms general observations of surface adsorption trends in terms of d-band center and binding energy as a function of coordination number, i.e., the stronger the molecular adsorption, the higher the d-band shifts at low-coordinated sites.

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