High-Throughput Computational Screening of Cubic Perovskites for Solid Oxide Fuel Cell Cathodes

It is a present-day challenge to design and develop oxygen-permeable solid oxide fuel cell (SOFC) electrode and electrolyte materials that operate at low temperatures. Herein, by performing high-throughput density functional theory calculations, oxygen vacancy formation energy, Evac, data for a pool of all-inorganic ABO3 and A I 0.5 A II 0.5 BO3 cubic perovskites is generated. Using E vac data of perovskites, the area-specific resistance (ASR) data, which is related to both oxygen reduction reaction activity and selective oxygen ion conductivity of materials, is calculated. Screening a total of 270 chemical compositions, 31 perovskites are identified as candidates with properties that are between those of state-of-the-art SOFC cathode and oxygen permeation components. In addition, an intuitive approach to estimate Evac and ASR data of complex perovskites by using solely the easy-to-access data of simple perovskites is shown, which is expected to boost future explorations in the perovskite material search space for genuinely diverse energy applications.</p

A density functional theory study of propylene epoxidation mechanism on Ag\u3csub\u3e2\u3c/sub\u3eO(001) surface

\u3cp\u3ePropylene oxide (PO) is one of the 50 most produced chemicals according to the production volume. Environmental and economic drawbacks of conventional PO production processes necessitate new production methods. Among the new production alternatives, direct epoxidation of propylene to propylene oxide by molecular oxygen is a highly desired method and seen as the holy grail of propylene epoxidation studies. In this study, the propylene epoxidation mechanism on an Ag\u3csub\u3e2\u3c/sub\u3eO(001) surface is investigated computationally by means of density functional theory (DFT) calculations using the Vienna Ab-initio Simulation Package (VASP). A perfect Ag\u3csub\u3e2\u3c/sub\u3eO(001) surface and a surface with one O vacancy are utilized for this purpose. It is found that propylene oxide can be directly formed on an Ag\u3csub\u3e2\u3c/sub\u3eO(001) surface whether there is an oxygen vacancy or not. The rate controlling step is PO desorption from both surfaces. PO isomers, i.e. acetone and propanal, can also be formed on these surfaces. However, activation barriers do exist for these molecules. Direct allyl formation on the Ag\u3csub\u3e2\u3c/sub\u3eO(001) surface is found to be unfavorable unlike what is proposed in the literature. On the other hand, it is observed that an allyl radical can be formed either via an oxametallocycle path or after the formation of propylene oxide. In fact, the discovered allyl radical formation pathway from propylene oxide is found as the most probable successive reaction pathway because of the high desorption barrier of PO.\u3c/p\u3

High-Throughput Computational Screening of Cubic Perovskites for Solid Oxide Fuel Cell Cathodes

It is a present-day challenge to design and develop oxygen-permeable solid oxide fuel cell (SOFC) electrode and electrolyte materials that operate at low temperatures. Herein, by performing high-throughput density functional theory calculations, oxygen vacancy formation energy, Evac, data for a pool of all-inorganic ABO3 and A I 0.5 A II 0.5 BO3 cubic perovskites is generated. Using E vac data of perovskites, the area-specific resistance (ASR) data, which is related to both oxygen reduction reaction activity and selective oxygen ion conductivity of materials, is calculated. Screening a total of 270 chemical compositions, 31 perovskites are identified as candidates with properties that are between those of state-of-the-art SOFC cathode and oxygen permeation components. In addition, an intuitive approach to estimate Evac and ASR data of complex perovskites by using solely the easy-to-access data of simple perovskites is shown, which is expected to boost future explorations in the perovskite material search space for genuinely diverse energy applications

A density functional theory study of propylene epoxidation mechanism on Ag2O(001) surface

Propylene oxide (PO) is one of the 50 most produced chemicals according to the production volume. Environmental and economic drawbacks of conventional PO production processes necessitate new production methods. Among the new production alternatives, direct epoxidation of propylene to propylene oxide by molecular oxygen is a highly desired method and seen as the holy grail of propylene epoxidation studies. In this study, the propylene epoxidation mechanism on an Ag2O(001) surface is investigated computationally by means of density functional theory (DFT) calculations using the Vienna Ab-initio Simulation Package (VASP). A perfect Ag2O(001) surface and a surface with one O vacancy are utilized for this purpose. It is found that propylene oxide can be directly formed on an Ag2O(001) surface whether there is an oxygen vacancy or not. The rate controlling step is PO desorption from both surfaces. PO isomers, i.e. acetone and propanal, can also be formed on these surfaces. However, activation barriers do exist for these molecules. Direct allyl formation on the Ag2O(001) surface is found to be unfavorable unlike what is proposed in the literature. On the other hand, it is observed that an allyl radical can be formed either via an oxametallocycle path or after the formation of propylene oxide. In fact, the discovered allyl radical formation pathway from propylene oxide is found as the most probable successive reaction pathway because of the high desorption barrier of PO

Surface charging activated mechanism change: A computational study of O, CO, and CO2 interactions on Ag electrodes

Electrocatalytic and plasma-activated processes receive increasing attention in catalysis. Density functional theory (DFT) calculations are state-of-the-art tools for the fundamental study of reaction mechanisms and predicting the performance of catalytic materials. Proper application of DFT-based methods is crucial when investigating charge-doped electrode surfaces during electrocatalytic and plasma-activated reactions. Here, as a model electrode for plasma-activated CO2 splitting, we studied the interactions of O, CO, and CO2 with the neutral and progressively charged Ag(111) metal surfaces. We show that the application of correction procedures is necessary to obtain accurate adsorption energy profiles of O atoms, CO and CO2 molecules on Ag surfaces that are under the influence of additional electrons. Interestingly, the oxidation of CO is found to shift from a Langmuir–Hinshelwood mechanism on a neutral electrode to an Eley–Rideal mechanism on charged electrodes. Furthermore, we show that the surface charging of Ag(111) electrodes increase their CO2 reduction performance by enhancing the adsorption of O atoms and desorption of CO molecules. A further increase in the absolute charge-state of the electrode surface is expected to waive the thermodynamic barriers for the CO2 splitting reaction

Surface charging activated mechanism change: A computational study of O, CO, and CO2 interactions on Ag electrodes

Electrocatalytic and plasma-activated processes receive increasing attention in catalysis. Density functional theory (DFT) calculations are state-of-the-art tools for the fundamental study of reaction mechanisms and predicting the performance of catalytic materials. Proper application of DFT-based methods is crucial when investigating charge-doped electrode surfaces during electrocatalytic and plasma-activated reactions. Here, as a model electrode for plasma-activated CO2 splitting, we studied the interactions of O, CO, and CO2 with the neutral and progressively charged Ag(111) metal surfaces. We show that the application of correction procedures is necessary to obtain accurate adsorption energy profiles of O atoms, CO and CO2 molecules on Ag surfaces that are under the influence of additional electrons. Interestingly, the oxidation of CO is found to shift from a Langmuir–Hinshelwood mechanism on a neutral electrode to an Eley–Rideal mechanism on charged electrodes. Furthermore, we show that the surface charging of Ag(111) electrodes increase their CO2 reduction performance by enhancing the adsorption of O atoms and desorption of CO molecules. A further increase in the absolute charge-state of the electrode surface is expected to waive the thermodynamic barriers for the CO2 splitting reaction

Packing of inhibitor molecules during area-selective atomic layer deposition studied using random sequential adsorption simulations

Area-selective atomic layer deposition (ALD) is of interest for applications in self-aligned processing of nanoelectronics. Selective deposition is generally enabled by functionalization of the area where no growth is desired with inhibitor molecules. The packing of these inhibitor molecules, in terms of molecule arrangement and surface density, plays a vital role in deactivating the surface by blocking the precursor adsorption. In this work, we performed random sequential adsorption (RSA) simulations to investigate the packing of small molecule inhibitors (SMIs) on a surface in order to predict how effective the SMI blocks precursor adsorption. These simulations provide insight into how the packing of inhibitor molecules depends on the molecule size, molecule shape, and their ability to diffuse over the surface. Based on the RSA simulations, a statistical method was developed for analyzing the sizes of the gaps in between the adsorbed inhibitor molecules, serving as a quantitative parameter on the effectiveness of precursor blocking. This method was validated by experimental studies using several alcohol molecules as SMIs in an area-selective deposition process for SiO2. It is demonstrated that RSA simulations provide an insightful and straightforward method for screening SMIs in terms of their potential for area-selective ALD

Computational investigation of precursor blocking during area-selective atomic layer deposition using aniline as a small molecule inhibitor

Area-selective atomic layer deposition using small-molecule inhibitors (SMIs) involves vapor-phase dosing of inhibitor molecules, resulting in an industry-compatible approach. However, the identification of suitable SMIs that yield a high selectivity remains a challenging task. Recently, aniline (C 6H 5NH 2) was shown to be an effective SMI during the area-selective deposition (ASD) of TiN, giving 6 nm of selective growth on SiO 2 in the presence of Ru and Co non-growth areas. In this work, using density functional theory (DFT) and random sequential adsorption (RSA) simulations, we investigated how aniline can effectively block precursor adsorption on specific areas. Our DFT calculations confirmed that aniline selectively adsorbs on Ru and Co non-growth areas, whereas its adsorption on the SiO 2 growth area is limited to physisorption. DFT reveals two stable adsorption configurations of aniline on the metal surfaces. Further calculations on the aniline-functionalized surfaces show that the aniline inhibitor significantly reduces the interaction of Ti precursor, tetrakis(dimethylamino)titanium, with the non-growth area. In addition, RSA simulations showed that the co-presence of two stable adsorption configurations allows for a high surface inhibitor coverage on both Co and Ru surfaces. As the surface saturates, there is a transition from the thermodynamically most favorable adsorption configuration to the sterically most favorable adsorption configuration, which results in a sufficiently dense inhibition layer, such that an incoming precursor molecule cannot fit in between the adsorbed precursor molecules. We also found that, as a result of the catalytic activity of the metallic non-growth area, further reactions of inhibitor molecules, such as hydrogenolysis, can play a role in precursor blocking