scholarly journals Competitive Adsorption of H2O and SO2 on Catalytic Platinum Surfaces: a Density Functional Theory Study

2021 ◽  
Vol 74 ◽  
Author(s):  
Marietjie J. Ungerer ◽  
David Santos-Carballal ◽  
Cornelia G.C.E. van Sittert ◽  
Nora H. de Leeuw
Keyword(s):  
Density Functional Theory ◽  
Adsorption Energy ◽  
Sulphur Dioxide ◽  
Density Functional ◽  
Competitive Adsorption ◽  
Hydrogen Adsorption ◽  
Surface Reactivity ◽  
Functional Theory ◽  
Sulphur Poisoning ◽  
Production Of Hydrogen

ABSTRACT Platinum has been widely used as the catalyst of choice for the production of hydrogen in the hybrid sulphur (HyS) cycle. In this cycle, water (H2O) and sulphur dioxide (SO2) react to form sulphuric acid and hydrogen. However, the surface reactivity of platinum towards H2O and SO2 is not yet fully understood, especially considering the competitive adsorption that may occur on the surface. In this study, we have carried out density functional theory calculations with long-range dispersion corrections [DFT-D3-(BJ)] to investigate the competitive effect of both H2O and SO2 on the Pt (001), (011) and (111) surfaces. Comparing the adsorption of a single H2O molecule on the various Pt surfaces, it was found that the lowest adsorption energy (Eads = -1.758 eV) was obtained for the dissociative adsorption of H2O on the (001) surface, followed by the molecular adsorption on the (011) surface (Eads = -0.699 eV) and (111) surface (Eads = -0.464 eV). For the molecular SO2 adsorption, the trend was similar, with the lowest adsorption energy (Eads = -2.471 eV) obtained on the (001) surface, followed by the (011) surface (Eads = -2.390 eV) and (111) surface (Eads = -1.852 eV). During competitive adsorption by H2O and SO2, the SO2 molecule will therefore preferentially adsorb onto the Pt surface. If the concentration of SO2 increases, self-reaction between two neighbouring SO2 molecules may occur, leading to the formation of sulphur monoxide (SO) and -trioxide (SO3) on the surface, which could lead to sulphur poisoning of the Pt catalytic surface. Keywords: Platinum, water, sulphur dioxide, hydrogen, adsorption, density functional theory.

scholarly journals Density Functional Theory Study of Metal and Metal-Oxide Nucleation and Growth on the Anatase TiO2(101) Surface

Computation ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 125
Author(s):  
Leila Kalantari ◽  
Fabien Tran ◽  
Peter Blaha
Keyword(s):  
Density Functional Theory ◽  
Metal Oxide ◽  
Adsorption Energy ◽  
Density Functional ◽  
Magnetic Moments ◽  
Experimental Studies ◽  
Anatase Tio2 ◽  
Functional Theory ◽  
Transition Electron Microscopy ◽  
Production Of Hydrogen

Experimental studies have shown the possible production of hydrogen through photocatalytic water splitting using metal oxide (MOy) nanoparticles attached to an anatase TiO2 surface. In this work, we performed density functional theory (DFT) calculations to provide a detailed description of the stability and geometry of MxOy clusters M = Cu, Ni, Co, Fe and Mn, x = 1–5, and y = 0–5 on the anatase TiO2(101) surface. It is found that unsaturated 2-fold-coordinated O-sites may serve as nucleation centers for the growth of metal clusters. The formation energy of Ni-containing clusters on the anatase surface is larger than for other M clusters. In addition, the Nin adsorption energy increases with cluster size n, which makes the formation of bigger Ni clusters plausible as confirmed by transition electron microscopy images. Another particularity for Ni-containing clusters is that the adsorption energy per atom gets larger when the O-content is reduced, while for other M atoms it remains almost constant or, as for Mn, even decreases. This trend is in line with experimental results. Also provided is a discussion of the oxidation states of M5Oy clusters based on their magnetic moments and Bader charges and their possible reduction with oxygen depletion.

scholarly journals Density functional theory insights into the bonding of CH3OH and CH3O with Ir(111) surface

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
Thong Le Minh Pham ◽  
Khoa Thanh Phung ◽  
Thang Viet Ho ◽  
Thi Anh Le ◽  
An Thai Thi Nguyen
Keyword(s):  
Density Functional Theory ◽  
Adsorption Energy ◽  
Density Functional ◽  
Molecular Characteristics ◽  
Functional Theory ◽  
Adsorption Structure ◽  
The Density Functional Theory ◽  
Production Of Hydrogen ◽  
Charge Analysis ◽  
The Difference

Introduction: Understanding the adsorption characteristics of CH3OH and CH3O on the noble metal surfaces is essential for designing better catalysts for the on-board production of hydrogen from CH3OH. This study aims to provide insights into the adsorption behavior of these molecules on Ir(111) surface. Methods: The adsorption structure, the adsorption energy, and the bonding mechanism of CH3OH and CH3O with Ir(111) surface were investigated by means of the density functional theory (DFT) calculations and the Bader charge analysis. Results: The DFT results show that the adsorption of CH3OH and CH3O is driven by the formation of Ir–O bond at the top site of the surface by the overlap of O-2p and Ir-5d orbitals. The overlap of these orbitals is greater in the absorption of CH3O, resulting in stronger adsorption energy of CH3O (2.23 eV vs. 0.32 eV). In agreement with the adsorption strength, the charge transfer from CH3O to the surface is significantly larger than from CH3OH (0.386 e vs. 0.073 e). Conclusion: Although driven by the same adsorption bond, the difference in the molecular characteristics leads to a marked difference in the absorption strength of CH3OH and CH3O on Ir(111) surface.

scholarly journals Density Functional Theory Study of Hydrogen Adsorption on Pt Pd/γ-Al2O3 Surface

2021 ◽  
Vol 2097 (1) ◽  
pp. 012020
Author(s):  
Liang Zhang ◽  
Jia Li ◽  
Yong Chen ◽  
Cheng Zeng ◽  
Wu Kang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Adsorption Energy ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
Energy Gap ◽  
Solid Catalyst ◽  
Functional Theory ◽  
Adsorption Sites ◽  
Lower Energy Level ◽  
Catalytic Hydrogen

Abstract At present passive hydrogen recombiners (PAR) are used to prevent hydrogen explosion. Hydrogen removal catalyst is the core component of PAR. The adsorption of hydrogen on the solid catalyst surface is the premise of catalytic hydrogen removal and is of great significance for deeper understanding of hydrogen removal mechanism. The adsorption behavior of H2-Pt Pd/γ-Al2O3 system has been studied by using density functional theory and periodic slab model. The results of different adsorption sites indicate the adsorption energy of top site is highest, which is -1.2584eV. Higher adsorption energy means stronger interaction between H2 and catalyst substrate, which elongates H-H bond and increases the negative charge on H2. With increasing doping content of Pd, the adsorption energy of substrate decreases gradually. The adsorption energy absolute value of Pt4/γ-Al2O3 is highest and its H-H bond is longest, arriving at 0.0967nm. After adsorbed on substrate, the energy gap of H2 decreases drastically with the lowest energy gap of H2-Pt4/γ-Al2O3 that is 0.5197eV, and the peaks of density of state pattern move to lower energy level. This is because that the d orbital of Pt/Pd atoms interacts with the τ* anti-bond orbital of H2 strongly, transferring electrons to the τ* anti-bond orbital of H2. Doping Pd increases the energy gap of molecule orbital.

scholarly journals Study of Hydrogen Adsorption on Pt and Pt-Based Bimetallic Surfaces by Density Functional Theory

2013 ◽  
Vol 29 (09) ◽  
pp. 1900-1906 ◽  
Author(s):  
GAO Zi-Feng ◽  
◽  
CHEN Hao ◽  
QI Sui-Tao ◽  
YI Chun-Hai ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
Functional Theory ◽  
Bimetallic Surfaces

Density functional theory-based investigation of hydrogen adsorption on zinc oxide (101¯0) surface: Revisited

2021 ◽  
Vol 703 ◽  
pp. 121726
Author(s):  
Manuel M. Balmeo ◽  
John Symon C. Dizon ◽  
Melvin John F. Empizo ◽  
Erick John Carlo D. Solibet ◽  
Verdad C. Agulto ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Zinc Oxide ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
Functional Theory

Density Functional Theory Calculations of Arsenic(III) Structures on Perfect TiO2 Anatase (1 0 1) Surface

2011 ◽  
Vol 233-235 ◽  
pp. 491-494 ◽  
Author(s):  
Lin Yu ◽  
Yue Liu ◽  
Zhi Gang Wei ◽  
Gui Qiang Diao ◽  
Ming Sun ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Adsorption Energy ◽  
Density Functional ◽  
Function Method ◽  
Photocatalytic Oxidation ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Low Concentrations ◽  
The Density Functional Theory ◽  
The World

There are many areas in the world where the ground water has been contaminated by arsenic. One process to purify the water is to use TiO2 to adsorb the arsenic. As the TiO2 surface can be cleaned and reused, it has a promising potential as a water purifier. In this paper, the plane-wave function method, based on the density functional theory, has been used to calculate the structures of arsenic(III) on a perfect TiO2 anatase (1 0 1) surface. All the arsenic(III) solution species such as H3AsO3, H2AsO3-1, HAsO3-2 and AsO3-3 are put onto the surface with many different possible structures to obtain the adsorption energy. Based on the adsorption energy, the bidentate binuclear (BB) adsorption configurations of arsenic(III) on the surface are more favorable at low concentrations, whereas BB form and monodentate mononuclear (MM) form may coexist at higher concentrations. The models and results fit well with published experimental results. The results and conclusions will be of benefit to further research on arsenite adsorption and its photocatalytic oxidation on a TiO2 surface.

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