Stable Adsorption Energies Research Articles

Computer Simulation Study of Lithium and Oxygen Adsorption on Ruthenium Dioxide (110) Surface

Metal oxides are widely considered as excellent catalysts in lithium-air batteries to promote the production of stable discharge products and achieve superior electrochemical performance. The lithium–air (Li–air) battery is a metal–air electrochemical cell or battery chemistry that uses oxidation of lithium at the anode and reduction of oxygen at the cathode to induce a current. Despite various studies exploring the use of metal oxides as effective catalysis, the catalytic activity of ruthenium oxide (RuO2) towards lithium and oxygen ions is not fully understood. In this work, we investigate the adsorptions of lithium and oxygen on the RuO2 (110) surface using density functional theory (DFT) method. Due of the size of the supercell, and assuming that oxygen atoms occupy bulk-like positions around the surface metal atoms, only five values of (gamma) Γ are possible if constraint to a maximum of 1 monolayer (ML) of adatoms or vacancies: Γ= 0 surface is the stoichiometric surface, Γ= 1, 2 are the partially and totally oxidised surfaces, and Γ=-1, -2 are the partially and totally reduced surfaces. The addition of two oxygen atoms revealed the most stable adsorption energy is the mono-clear followed by bridging configuration. The lithium orientation between two bridging oxygen and in plane oxygen (bbi) orientation is much more stable, thus lithium generally prefers to adsorb where it will be triply coordinated to two bridging oxygen atoms and one in plane oxygen atom. Rutile RuO2 has been widely considered as an excellent catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in non-aqueous.

Dual Improvement in Sensitivity and Humidity Tolerance of a NO2 Sensor Based on 3-Aminopropyltriethoxysilane Self-Assembled Monolayer-Functionalized SnSe2 for Explosive Photolysis Gas Detection

Explosives can be analyzed for their content by detecting the photolytic gaseous byproducts. However, to prevent electrostatic sparking, explosives are frequently preserved in conditions with low temperatures and high humidity, impeding the performance of gas detection. Thus, it has become a research priority to develop gas sensors that operate at ambient temperature and high humidity levels in the realm of explosive breakdown gas-phase detection. In this work, 3-aminopropyltriethoxysilane (APTES) self-assembled monolayer-functionalized tin diselenide (APTES-SnSe2) nanosheets were synthesized via a facile solution stirring strategy, resulting in a room-temperature NO2 sensor with improved sensitivity and humidity tolerance. The APTES-SnSe2 sensor with moderate functionalization time outperforms the pure SnSe2 sensor in terms of the response value (317.51 vs 110.98%) and response deviation (3.11 vs 24.13%) under humidity interference to 500 ppb NO2. According to density functional theory simulations, the stronger adsorption of terminal amino groups of the APTES molecules to NO2 molecules and stable adsorption energy in the presence of H2O are the causes of the improved sensing capabilities. Practically, the APTES-SnSe2 sensor achieves accurate detection of photolysis gases from trace nitro explosives octogen, pentaerythritol tetranitrate, and trinitrotoluene at room temperature and various humidity levels. This study provides a potential strategy for the construction of gas sensors with high responsiveness and antihumidity capabilities to identify explosive content in harsh environments.

Understanding Cd2+ Adsorption Mechanism on Montmorillonite Surfaces by Combining DFT and MD

The adsorption mechanism of Cd2+ on different cleavage planes of montmorillonite was investigated using density functional theory (DFT) calculations and molecular dynamics (MD) simulations. The most stable adsorption energies of Cd2+ on the (001) and (010) surfaces were −88.74 kJ/mol and −283.55 kJ/mol, respectively. On the (001) surface, Cd2+ was adsorbed on the centre of the silicon–oxygen ring by electrostatic interactions, whereas on the (010) surface, Cd2+ was adsorbed between two ≡Al–OH groups and formed two covalent bonds with O, which was mainly due to the interaction between the Cd s and O p orbitals. Upon the partial substitution of Na+ by Cd2+, Cd2+ was adsorbed on the (001) surface as inner-sphere surface complexes, with a hydration number of 5.01 and a diffusion coefficient of 0 m2/s. Whereas, when Cd2+ completely replaced Na+, part of the Cd2+ moved from the inner-sphere surface complexes to the outer-sphere surface complexes owing to its competitive adsorption. In this case, its hydration number became 6.05, and the diffusion coefficient increased to 1.83 × 10−10 m2/s. This study provides the theoretical background necessary for the development of montmorillonite-based adsorbents.

Adsorption behavior of anticancer drug on the aluminum nitride surface: Density functional theory evolution

We evaluated the detection of fluorouracil (5FU) by means of an AlN nanocage using density functional theory (DFT) calculations. Different drug sites, which contain oxygen, fluorine and oxygen atoms, were adsorbed on the surface of the AlN nanocage to achieve the most stable AlN/5FU state, and the most stable adsorption energy which is equal to −61.08 kJ/mol was related to the interaction of Al metal with a F atom of 5FU. It is also suggested that an electrostatic interaction is accompanied by the process of drug adsorption on the surface of the AlN nanocage. The electrical conductivity of the AlN nanocage is raised drastically up to 21.5% after the adsorption of 5FU on the surface of the AlN nanocage. This increase in the conductivity can be considered as a signal to detect the drug. Therefore, the work function of the AlN nanocage is reduced from 4.5 eV to 3.68 eV after the adsorption of 5FU. This reduction is induced by the instant bipolarity caused by the induction of a positive charge on the AlN nanocage as well as a negative charge on 5FU. The findings obtained from the aqueous medium analysis show that the 5FU/AlN complex is more stable in the aqueous phase than in the gas phase.

Mechanistic investigations of N-doped graphene/2H(1T)-MoS2 for Li/K-ions batteries

Abstract N-doped graphene (NGr) incorporated with 2H-MoS2 and 1T-MoS2 (NGr/2H(1T)-MoS2) composites have been explored as anode materials for Li/K-ions batteries (LIBs/PIBs), however, the electrochemical mechanisms of their performance have not been well probed. In this work, we use first-principles calculations to investigate the atomic mechanisms associated with their high performance and cycling stability. Graphitic N (grN) is found to play a vital role in improving the structural stability of NGr/2H(1T)-MoS2 and the electronic conductivity of NGr/2H-MoS2, while pyridinic N and pyrrolic N are detrimental to the structural integrity of hybrids. Due to small and stable adsorption energies, fast Li+/K+ adsorption can be achieved in grNGr/2H(1T)-MoS2 hybrids at high Li+/K+ contents. Besides, grNGr/2H(1T)-MoS2 composites have low Li+/K+ diffusion energy barriers and large diffusion coefficients. Especially, grNGr/1T-MoS2 displays superior Li+/K+ adsorption and diffusion capabilities as well as high electronic conductivity, making it a promising anode material for LIBs/PIBs. Based on the lattice expansion during K+ insertion, an optimal range of interlayer distance (6.0–6.5 A) is found. These findings provide an in-depth understanding on the microscale Li+/K+ storage behaviour and are also instructive for optimising NGr/2H-MoS2 composite and designing NGr/1T-MoS2 anode material of LIBs/PIBs.

Density Functional Theory Study of Dopant Effect on Sintering in the Anode of Solid Oxide Fuel Cell

Sintering of Ni particles in the Ni/Y-doped ZrO2 anode is a major obstacle to the widespread use of solid oxide fuel cell. In this study, we investigated the dopant effect on the diffusion of a Ni atom on the ZrO2 surface with dopants (Y and Al) by density functional theory calculations in order to inhibit the sintering. The most stable adsorption sites of the Ni atom on the Al-doped and Y-doped ZrO2 surfaces are the vicinity of the twofold-coordination oxygen atom and the vicinity of an oxygen vacancy, respectively. It is found that the most stable adsorption energy on the Al-doped ZrO2 surface is larger than that on the Y-doped ZrO2 surface. The analysis of diffusion path based on the potential energy surfaces of the Ni atom on the two surfaces shows that the energy barrier for the diffusion of the Ni atom on the Al-doped ZrO2 surface is larger than that on the Y-doped ZrO2 surface. The diffusion of the Ni atom on the Al-doped ZrO2 surface is more difficult than that on the Y-doped ZrO2 surface. This is because the Ni atom strongly bound to the twofold-coordination oxygen atom and the Ni atom is constrained in the Al-doped ZrO2 surface. Thus, the Ni sintering on the Al-doped ZrO2 surface is inhibited compared to that on the Y-doped ZrO2 surface.

A first principles study of water adsorption on α-Pu (0 2 0) surface

Adsorptions of water in molecular (H2O) and dissociative (OH+H, H+O+H) configurations on the α-Pu (020) surface have been studied using ab initio methods. The full-potential FP/LAPW+lo method has been used to calculate the adsorption energies at the scalar relativistic with no spin–orbit coupling (NSOC) and fully relativistic with spin–orbit coupling (SOC) theoretical levels. It is found that the SOC effect increases the adsorption energies by ∼0.30eV for the two dissociative adsorptions. Weak physisorptions have been observed for the molecule H2O on the α-Pu (020) surface with primarily a covalent bonding, while the two dissociative adsorptions are chemisorptive with ionic bonding. The one-fold top site with an almost flat-lying orientation is found to be the most stable site for the adsorbed H2O molecule. At the SOC level, the most stable adsorption energy is 0.58eV, the corresponding values being 5.44eV and 5.73eV for the partial dissociation and complete dissociation cases, respectively. The analysis of the local projected density of states shows that the surface Pu-5f electrons remain primarily chemically inert in the molecular water adsorption process. Completely dissociative adsorption at a long bridge site for the dissociated O atom and two short bridge sites for the two dissociated H atoms is the most stable adsorption site. Hybridizations of O(2p)–H(1s)–Pu(5f)–Pu(6d) are observed for the two dissociative adsorptions, implying that some of the Pu-5f electrons become further delocalized and participate in chemical bonding. Work functions decrease for the molecular and the partial adsorption processes while it increases for complete dissociation.