ORCID Profile
0000-0002-4489-2050
Current Organisation
Clariant International AG
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Publisher: Elsevier BV
Date: 08-2012
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CP41392B
Abstract: As a first step towards a microscopic understanding of single-Pt atom-dispersed catalysts on non-conventional TiN supports, we present density-functional theory (DFT) calculations to investigate the adsorption properties of Pt atoms on the pristine TiN(100) surface, as well as the dominant influence of surface defects on the thermodynamic stability of platinized TiN. Optimized atomic geometries, energetics, and analysis of the electronic structure of the Pt/TiN system are reported for various surface coverages of Pt. We find that atomic Pt does not bind preferably to the clean TiN surface, but under typical PEM fuel cell operating conditions, i.e. strongly oxidizing conditions, TiN surface vacancies play a crucial role in anchoring the Pt atom for its catalytic function. Whilst considering the energetic stability of the Pt/TiN structures under varying N conditions, embedding Pt at the surface N-vacancy site is found to be the most favorable under N-lean conditions. Thus, the system of embedding Pt at the surface N-vacancy sites on TiN(100) surfaces could be promising catalysts for PEM fuel cells.
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CP23534J
Abstract: As a first step towards a microscopic understanding of supported ultrathin nanofilms of TiN, we present state-of-the-art density-functional theory (DFT) calculations to investigate the interfacial properties of the TiN/MgO system as a function of film thickness. Optimized atomic geometries, energetics, and analysis of the electronic structure of the TiN/MgO systems are reported. In particular, we find that the work function of 1 ML of TiN(100) on MgO(100) exhibits a significant decrease, rationalized by the large surface dipole moment formation due to the changes in charge densities at the interface of this system. This decrease in the work function of TiN/MgO systems (as compared to pristine MgO(100) surface) could well benefit their application in metal-oxide-semiconductor devices as an ideal gate-stack material.
Publisher: AIP Publishing
Date: 04-2009
DOI: 10.1063/1.3103327
Abstract: A promising material for hydrogen storage at room temperature–Al doped graphene is proposed theoretically by using density functional theory calculation. Hydrogen storage capacity of 5.13 wt % is predicted at T=300 K and P=0.1 GPa with an adsorption energy Eb=−0.260 eV/H2. This is close to the target specified by U.S. Department of Energy with a storage capacity of 6 wt % and a binding energy of −0.2 to −0.4 eV/H2 at ambient temperature and modest pressure for commercial applications. It is believed that the doped Al alters the electronic structures of both C and H2. The bands of H2 overlapping with those of Al and C simultaneously are the underlying mechanism of hydrogen storage capacity enhancement.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP53334D
Abstract: It has been previously reported that the system of single Pt atoms embedded in N-vacancy (V(N)) sites on the TiN(100) surface (Pt-TiN) could be a promising catalyst for proton exchange membrane fuel cells (PEM FCs). The adsorption of molecules on Pt-TiN is an important step, when it is incorporated as the anode or cathode of PEM FCs. Utilizing first principles calculations based on density functional theory, systematic investigations are performed on the adsorption of several atomic and molecular species on the Pt-TiN system, as well as the co-adsorption of them. The favorable binding sites and adsorption energies of several molecular species, namely carbon dioxide (CO2), carbon monoxide (CO), oxygen (O2), hydrogen (H2), hydroxyl (OH), an oxygen atom (O), and a hydrogen atom (H), are explored. For each, the adsorption energy and preferred binding site are identified and the vibrational frequencies calculated. It is found that CO2, CO and H prefer the Pt top site while OH and O favorably adsorb on the Ti top site. When CO and OH are co-adsorbed on the Pt-TiN(100) surface, OH weakens the adsorption of CO. The weakening effect is enhanced by increasing the coverage of OH. A similar behavior occurs for H and OH co-adsorption on the Pt-TiN(100) surface. Because co-adsorption with OH and H species weakens the adsorption of CO on Pt-TiN, it is expected that the acid and base conditions in PEM FCs could mitigate CO poisoning on functionalized Pt-TiN surfaces.
No related grants have been discovered for Renqin Zhang.