Large Adsorption Energy Research Articles

Combined first-principles and machine learning study of the initial growth of carbon nanomaterials on metal surfaces

To understand the effects of H of hydrocarbon precursors and alloying elements of catalysts on the initial growth of carbon nanomaterials, this work combined first-principles (FP) calculation and machine learning (ML) methods to study the adsorption of complete hydrocarbon molecules on various alloy surfaces. Specifically, we calculated the energetics and geometries of the adsorption of acetylene (C2H2) molecules on the pristine Ni, Co, and Fe metal and a benzene molecule on Ni-X [X = thirty 3d, 4d, and 5d transition metal (TM) elements] alloy surfaces. The results suggest that benzene has larger adsorption energies on Ni-X (X = Y, Cd, Sc, Lu, Ag, Ti, Hg, Pd, Zn, V, Cu, and Au) than that on the pristine Ni surface. Furthermore, the ML models were constructed using the surface “Center-Environment” (SCE) features to predict the FP results. The ML models suggest that the features critical to adsorption energies include the size, electronegativity, and valence of the doping element. We proposed an “add and dehydrogenate” mechanism underlying the initial growth of nanocarbon with hydrocarbon precursors. These results provide a theoretical basis in the design of alloy catalysts including in-plane single atom catalysts.

DFT insights into the adsorption mechanism of five-membered aromatic heterocycles containing N, O, or S on Fe(1 1 0) surface

Understanding the interaction of five-membered aromatic heterocycles with Fe(110) surface is crucial to the design of novel inhibitors against the corrosion of iron and steel. Herein, we report a detailed study of the adsorption properties and the bonding mechanism of pyrrole, furan, and thiophene on Fe(110) surface employing density functional theory (DFT) calculations. In the most stable adsorption geometries, the adsorbates lie flat at the hollow site and form covalent bonds with surface Fe atoms. The chemisorptions are demonstrated by large adsorption energies and charge transfers from Fe(110) to the adsorbates. Taking vdW corrections into account in the DFT calculations has a minimal effect on the adsorption geometries whereas it significantly increases the adsorption energies. The energetic and structural analysis demonstrates large molecular distortion induced by the adsorbate–surface interaction, and thiophene experiences the least molecular distortions, thereby having the largest adsorption energy among the adsorbates. The electronic structure analysis reveals that the electronic interactions of pyrrole, furan, and thiophene and Fe(110) are due to the overlaps of the frontier molecular orbitals with Fe-3dz2 and Fe-(3dxz + 3dyz) states. The charge transfer between the adsorbates and Fe(110) are elucidated by the charge density difference plot and Bader charge analysis.

The adsorption characteristics of CO, NO and NO2 on two dimensional metalloporphyrin porous nanosheets: A first-principles study

The toxic gas molecules (TGMs) emitted from coal burning have caused great damage to environment and people’s health, so it is urgent to design effective gas sensors to detect and remove TGMs. In this work, two-dimensional metalloporphyrin porous grid nanosheets (MPP-Grids) with transition metal atom center (M = Fe, Co and Zn) were predicted to be stable structures with sufficient and high-density active sites, which could adsorb and detect toxic gases. Based on density functional theory, the bonding characteristics, temperature effect, electronic and magnetic properties of MPP-Grids adsorbed with CO, NO and NO2 were investigated. FePP-Grid was the best adsorbent for removing CO, NO and NO2 simultaneously with larger adsorption energies. According to different magnetic moment changes from −1.71 μB to 0.00, 0.96 and 0.01 μB, FePP-Grid could detect and distinguish CO, NO and NO2 in the way of detecting magnetic properties without direct contact. And ZnPP-Grid could detect and distinguish NO and NO2 in the same way. Therefore, FePP-Grid and ZnPP-Grid were promising gas sensors, which could be used for the detection of CO, NO and NO2.

A computational study of direct CO2 hydrogenation to methanol on Pd surfaces.

The reaction mechanism of direct CO2 hydrogenation to methanol is investigated in detail on Pd (111), (100) and (110) surfaces using density functional theory (DFT), supporting investigations into emergent Pd-based catalysts. Hydrogen adsorption and surface mobility are firstly considered, with high-coordination surface sites having the largest adsorption energy and being connected by diffusion channels with low energy barriers. Surface chemisorption of CO2, forming a partially charged CO2δ-, is weakly endothermic on a Pd (111) whilst slightly exothermic on Pd (100) and (110), with adsorption enthalpies of 0.09, -0.09 and -0.19 eV, respectively; the low stability of CO2δ- on the Pd (111) surface is attributed to negative charge accumulating on the surface Pd atoms that interact directly with the CO2δ- adsorbate. Detailed consideration for sequential hydrogenation of the CO2 shows that HCOOH hydrogenation to H2COOH would be the rate determining step in the conversion to methanol, for all surfaces, with activation barriers of 1.41, 1.51, and 0.84 eV on Pd (111), (100) and (110) facets, respectively. The Pd (110) surface exhibits overall lower activation energies than the most studied Pd (111) and (100) surfaces, and therefore should be considered in more detail in future Pd catalytic studies.

Ultrafast charge transfer in a nonfullerene all-small-molecule organic solar cell: a nonadiabatic dynamics simulation with optimally tuned range-separated functional.

Herein, we have employed linear-response time dependent density functional theory (LR-TDDFT)-based nonadiabatic dynamics simulations to investigate the ultrafast charge transfer in a nonfullerene all-small-molecule donor-acceptor (D-A) system formed by a porphyrin small-molecule donor ZnP and a recently developed nonfullerene small-molecule acceptor 6TIC, during which the optimally tuned range-separated hybrid (OT-RSH) functional was adopted. In combination with static electronic structure calculations, several important conclusions were drawn. Firstly, the ZnP and 6TIC are more likely combined together non-covalently in parallel rather than in perpendicular to form ZnP-6TIC due to the much larger adsorption energies, i.e. -44.6 kcal mol-1vs. -25.2 kcal mol-1. Secondly, the excited state properties obtained by OT-RSH functionals seem more consistent with the experimental results compared to their untuned versions. Specifically, the energy of the lowest charge transfer (CT) state was predicted to be smaller than the lowest lying local excitation (LE) states using the OT-RSH functional-based LR-TDDFT calculations, which is beneficial for the charge transfer process that might be crucial for the high power conversion efficiency (PCE) achieved experimentally. In contrast, the untuned RS functionals all predict higher CT state energies, which is contradictory to the high PCE obtained in the experiment. Moreover, strong hybridization upon excitation between these states was revealed, which might be one of the reasons responsible for the high PCE observed in the experiment. Finally, ultrafast excited state relaxation can be completed within 500 fs due to the small energy gaps and the strong nonadiabatic couplings between these states, which is accompanied by ultrafast photoinduced electron transfer from ZnP to 6TIC and photoinduced hole transfer the other way around. The efficient charge transfer processes and the involvement of two charge generation channels might be another cause resulting in the excellent photovoltaic performance of ZnP-6TIC based OSCs. Our present work not only provides solid evidence for elucidating the underlying mechanism observed in previous experiments, but also suggests that the combination of OT-RSH functionals and LR-TDDFT-based nonadiabatic dynamics simulations might be a powerful tool for investigating the excited state dynamics of organic D-A systems, which is crucial for the theoretical design of novel OSCs with better performances in the future.

High-Polarity Fluoroalkyl Ether Electrolyte Enables Solvation-Free Li+ Transfer for High-Rate Lithium Metal Batteries.

Lithium metal batteries (LMBs) have aroused extensive interest in the field of energy storage owing to the ultrahigh anode capacity. However, strong solvation of Li+ and slow interfacial ion transfer associated with conventional electrolytes limit their long‐cycle and high‐rate capabilities. Herein an electrolyte system based on fluoroalkyl ether 2,2,2‐trifluoroethyl‐1,1,2,3,3,3‐hexafluoropropyl ether (THE) and ether electrolytes is designed to effectively upgrade the long‐cycle and high‐rate performances of LMBs. THE owns large adsorption energy with ether‐based solvents, thus reducing Li+ interaction and solvation in ether electrolytes. With THE rich in fluoroalkyl groups adjacent to oxygen atoms, the electrolyte owns ultrahigh polarity, enabling solvation‐free Li+ transfer with a substantially decreased energy barrier and ten times enhancement in Li+ transference at the electrolyte/anode interface. In addition, the uniform adsorption of fluorine‐rich THE on the anode and subsequent LiF formation suppress dendrite formation and stabilize the solid electrolyte interphase layer. With the electrolyte, the lithium metal battery with a LiFePO4 cathode delivers unprecedented cyclic performances with only 0.0012% capacity loss per cycle over 5000 cycles at 10 C. Such enhancement is consistently observed for LMBs with other mainstream electrodes including LiCoO2 and LiNi0.5Mn0.3Co0.2O2, suggesting the generality of the electrolyte design for battery applications.

Magnetic transitions in CO adsorption on graphene-based surfaces

Density functional theory was used to study carbon monoxide adsorption on several graphene-based surfaces. The surfaces were based on oxygen ions adsorbed (and without oxygen adsorption) on double- and triple-vacancy graphene and on a particular N-doped graphene surface. Magnetic transition, the largest adsorption energy (-6.5 eV) and CO reduction, occur in a proposed and more sensitive stationary point of the triple-vacancy graphene surface after CO adsorption. Oxygen adsorption on the former triple-vacancy graphene surface produces magnetic transition, chemisorption (-2.4 eV) forming an ester and CO oxidizes all after CO adsorption. The magnetic transition observed in both systems is correlated with charge transfer. Following the results of molecular dynamics the magnetic order prevails even at room temperature (T=300 K) in the former two systems. The results presented in this work could be useful for the development of magnetic CO sensors.

Adsorption of hazardous gases on poly(3,4‐ethylenedioxythiophene): Density functional theory study

AbstractWe have studied the adsorption of different hazardous gases (such as SO3, NH3, NO2, and H2S) on poly(3,4‐ethylenedioxythiophene) (PEDOT) to manifest it as a gas sensor using density functional theory (DFT). Both chemisorption and physisorption channels have been investigated to reveal the interaction pathway between PEDOT and hazardous gases. PEDOT can interact with SO3, NH3, NO2, and H2S via a physisorption channel with corresponding adsorption energies −13.32, −6.88, −6.02, and −7.47 kcal/mol, respectively. The chemisorptive nature has been observed only for SO3. But this pathway is kinetically and thermodynamically less accessible compared to the physisorption channel. The large adsorption energy value for SO3 (−13.32 kcal/mol) shows the better sensitivity of PEDOT towards SO3 compared to the rest three gases. The electronic properties of PEDOT vary based on its interaction with different gases. The frontier molecular orbitals, band gap, natural bond orbital charge, UV–vis spectra, and conductivity studies support the fact. The external electric field has been applied as a technique to tune the recovery time for SO3.

Mechanistic insights into the electrochemical Li/Na/K-ion storage for aqueous bismuth anode

Bismuth (Bi) was evaluated recently as an alloy-type anode material for aqueous alkali-metal ion batteries (ARABs) on account of its high theoretical capacity (385 mAh g−1), low redox potential (∼ −0.8 V vs. SCE), dendrite-free and absence of memory effects. However, it remains challenging for clarifying and pinpointing the intrinsic interaction mechanism between Bi and alkali metal ions (Li+, Na+ and K+), which is significant to reveal the potential and limitation of Bi electrode for future applications in ARABs. Herein, we gain the insights into the similarity and divergence of the (de)alloying mechanism of aqueous Bi electrode for AM ions (Li+, Na+ and K+) storage by ex-XANES, SXES, HRTEM and DFT. As a result, Bi shows superior specific capacities for Na+ and K+ storage but the lowest capacity for Li+ storage. Large adsorption energy makes Li+ dealloy from Bi matrix irreversibly, causing inferior rate performance and cycling stability. The largest radius of K+ triggers large volume expansion, which is responsible for the poor cycling stability for K+ storage. Bi exhibits superior performance for Na+ storage owning to the appropriate interaction strength between Bi and Na+. Our work can provide a proof-of-concept to universally pinpoint interactions between electrode and charge carriers for a wide range of metal electrodes.

Triple-atom catalysts 3TM-GYs (TM = Cu, Fe, and Co; GY = graphyne) for high-performance CO2 reduction reaction to C1 products

Atomically dispersed catalysts are promising materials for alleviating greenhouse effect and reproducing valuable chemical products through electrochemical CO2 reduction reaction (CO2RR). Here, earth-abundant triple transition metals (TM = Cu, Fe, and Co) anchored on graphyne (3TM-GY) were evaluated in CO2RR to C1 products by using density functional theory. Structural analyses showed that 3TM-GYs had high cohesive energy ranging from 6.91 to 6.98 eV/atom, and large binding energy ranging from 2.28 to 5.95 eV, guaranteeing structural stability in CO2RR. Electronic structure analyses confirmed the evident orbital overlap and large charge transfer between the triple TM atoms and direct-connected C atoms. The unique triangular TM trimer on GY facilitated the “point-to-point” activation of CO2 with large adsorption energy and distinctly bent configuration, providing a favorable adsorption and initial activation environment in CO2RR. 3Cu-GY exhibited a prior CO2 reduction product of CH4 with a low limiting potential of −0.41 V and high selectivities over other C1 products of 102 – 108, which surpassed the vast majority of atomically dispersed electrocatalysts. When applied potential was increased, CO2RR on 3Cu-GY had a great advantage in the high-throughput reaction processes toward HCOOH and CH4, whereas that on 3Fe-GY/3Co-GY had a great advantage toward high-reduction degree products of CH3OH and CH4. Moreover, hydrogen evolution reaction was severely inhibited, and CO2RR exhibited an overwhelming advantage over HER. This work demonstrated that graphyne was a suitable substrate material for constructing favorable coordination environment anchoring triple atom, and highlighted the advance of triple-atom catalysts for high-performance CO2RR.

Adsorption characteristics of citric acid on Fe3O4 (001), (011), and (111) surfaces.

Magnetite (001), (011), and (111) surfaces were the focus of our study. Magnetite (001) surface has two different terminations, that is, Fetet and 2Feoct4O. Magnetite (011) surface has two different terminations, that is, 2Feoct4O and 2Fetet2Feoct4O. Magnetite (111) surface has six different terminations, that is, Fetet1, Feoct, Fetet2, 3Feoct, 4O1, and 4O2. Comparing surface energies of (001), (011), and (111) surfaces, (001) has the smallest surface energy, and (111) has the largest surface energy except for Feoct termination, which means that (001) surface is the easiest to be cleaved, followed by (011) and (111) surfaces. Comparing adsorption energies of citric acid onto (001), (011), and (111) surfaces, (111) has the largest adsorption energies except for Fetet2 termination, and (001) has the smallest adsorption energies, which means that (111) surface is the most active for citric acid adsorption, followed by (011) and (001) surfaces. PDOS (partial density of states) of citric acid adsorbed onto (001), (011), and (111) surfaces with different terminations shows that 3d orbital of Fe of magnetite surface does not contribute to the adsorption, and 4s orbital of Fe of magnetite surface and 2s and 2p orbitals of O of citric acid contribute to the adsorption.

Hollow nanotubes carbon@tellurium for high-performance Al-Te batteries

In Al-Te batteries, the dissolution of tellurium and tellurium chloroaluminate compounds during the electrochemical reaction will seriously affect its electrochemical performance. In order to avoid this problem, we prepared hollow nanotube carbon-coated tellurium electrode materials, whose coating will increase electronic conductivity and avoid the collapse of structure caused by volume expansion during charging and discharging. The most important thing is that the dissolution of the tellurium and tellurium chloroaluminate compounds is greatly reduced due to the presence of the carbon coating. In addition, the results of density functional theory (DFT) show that AlCl4− has a large adsorption energy and a low diffusion barrier on Te (101) surface, which makes it exhibits excellent electrochemical performance. Its first discharge specific capacity is 1131.9 mAh g−1 at 200 mA g−1 and the initial discharge voltage is about 1.45 V. In addition, after 1000 cycles, the discharge specific capacity is still 254.2 mAh g−1 at 500 mA g−1. Interestingly, the electrochemical performance of hollow nanotubes carbon-coated tellurium is superior to that the related aluminum-based batteries recorded in the literature. Therefore, our work will lay a certain experimental and theoretical basis for the optimization of charging and discharging performance of Al-Te and other related secondary rechargeable batteries.

Zeolitic imidazolate framework enables practical room-temperature operation of solid-state lithium batteries

The decent flexibility and processability of solid-state polymer electrolytes (SPEs) endow them with broad development prospects in the solid-state lithium-based batteries field. Nevertheless, the poor room-temperature ionic conductivity of SPEs severely hinders their practical applications. Herein, we design a functionalized poly (vinylidene fluoride) (PVDF)-based electrolyte, and an ionic conductivity elevation is achieved by directly introducing zeolitic imidazolate framework-90 (ZIF-90) as filler into SPE. The metal ion sites of ZIF-90 can adsorb TFSI− with a large adsorption energy of −1.35 eV to facilitate the dissociation of LiTFSI. The SPE modified with ZIF-90 delivers the prominent ionic conductivity of 0.62 mS cm−1 at 30 °C and the low activation energy of 0.20 eV. Simultaneously, cells fabricated with LiFePO4 cathode exhibit the high specific discharge capacity of 118 mAh g−1 after 300 cycles at 1 C (0.44 mA cm−2) at room temperature. This work provides an efficient and promising strategy of fabricating competitive SPEs for solid-state lithium-based batteries.

Demonstration of Controlled Hydrogen Release Using Rh@GQDs during Hydrolysis of NH3BH3.

Achieving the controlled release of H2 through an effective approach still faces many challenges. Herein, high-quality graphene quantum dots (GQDs) are synthesized from a new precursor, 1,2,4-trihydroxy benzene, and a multifunctional platform of Rh@GQDs is further developed for the controlled H2 evolution upon the hydrolysis of NH3BH3 (AB). More importantly, the designing concepts of multistep and stepless speed controls have been introduced in the domains of both H2 evolution for the first time. Through a novel designing protocol, the rate of H2 evolution can be freely regulated and constantly varied on demand by means of chelation between Zn2+ and ethylene diamine tetraacetic acid (EDTA). The density functional theory calculation indicates that Zn2+ has the priority to be adsorbed onto Rh(100) due to its larger adsorption energy (107.98 kcal·mol-1) than that of AB (36.36 kcal·mol-1). A controlling mechanism is presented such that Zn2+ will cover the active sites of the nanocatalyst to prevent the H2 evolution, and EDTA can chelate Zn2+ to reactivate the nanocatalyst for the production of H2, greatly facilitating use of this strategy in other catalytic reactions. Moreover, it is demonstrated that the protocol is equally valid for diverse hydrogen storage materials. Therefore, this work not only establishes whole new concepts for the controlled production of H2 but also explains their mechanism, thus remarkably advancing the utilization of H2 energy and significantly enlightening the controlled process of catalysis.

The mechanism by which FeS2 promotes the bioleaching of CuFeS2: An electrochemical and DFT study

The impact of pyrite (FeS2) on the bioleaching of chalcopyrite (CuFeS2) was studied, and related mechanisms were elucidated by combining electrochemical experiments and first-principles density functional theory (DFT) calculations. The bioleaching experimental results show that after mixing with FeS2, the bioleaching rate for CuFeS2 is promoted by more than 3.5 times, and the best mass mixing ratio (FeS2: CuFeS2) is 1:1, which leads to an increase in the CuFeS2 bioleaching rate of 14% to 63%. The electrochemistry results show that after mixing with FeS2, an FeS2-CuFeS2 galvanic cell is formed, the corrosion current density is increased from 0.01997 mA·cm−2 to 0.5813 mA·cm−2, the redox reaction current density is enhanced, and the ion exchange resistance is decreased from 330.2 Ω·cm−2 to 167.4 Ω·cm−2, indicating that the FeS2 promotes the oxidation of CuFeS2, leading to a faster electronic delivery efficiency. The DFT results show that the S-Fe bonding between the CuFeS2 (001) and FeS2 (100) surfaces is weak; the work functions of FeS2-CuFeS2 decrease from 330.2 Ω·cm−2 to 167.4 Ω·cm−2, indicating a faster electron transfer; the electrons are transferred from CuFeS2 to FeS2 with the Fe atoms of FeS2 acting as the main electron acceptors; after mixing, glucose can be more easily adsorbed onto the CuFeS2 surface, resulting in stronger bonds, larger adsorption energies, and greater electron transfer, elaborating well on the bioleaching and electrochemical results.

First-principles study of two-dimensional material Cr2B2 as catalyst for electrochemical nitrogen reduction reaction

• The catalytic performance of Cr 2 B 2 for NRRby using DFT method. • There is an excellent NRR catalytic activity when N 2 adsorbed Cr-B bond. • The limiting potential can be reduced by N N breaking to acquire better NRR performance. Electrochemical nitrogen reduction reaction (NRR) is becoming increasingly promising alternatively to the traditional Haber-Bosch process but developing efficient electrocatalysts is still a challenge. In this job, we searched that the catalytic performance of Cr 2 B 2 for NRR by way of density functional theory (DFT) calculations. We mainly screened out four favorable N 2 adsorbed structures, including N 2 adsorption on the B-B bonds, Cr-B bonds, top site of B and Cr atom. It was found that the largest adsorption energy was −1.235 eV when N 2 was adsorbed on the Cr-B bond in a side-on structure, and has a better excellent NRR catalytic activity with the limiting potential is 0.29 V. The catalytic activity of all structures was better in the alternating mechanism of nitrogen reduction reaction. As the antibonding orbitals approach the Fermi level, the number of electrons in the antibonding orbitals increases. The limiting potential of T Cr _end can also be reduced from 0.88 V to 0.35 V by N N bond breaking after the second hydrogen, which contribute to the greater NRR performance. We hope that this research will offer a viable strategy for the design of NRR catalysts, and offer a new way of thinking for MBene as a catalyst for NRR.

Transition-metal-free boron doped SbN monolayer for N2 adsorption and reduction to NH3: A first-principles study

Electrochemical nitrogen reduction reaction (NRR) in ambient condition is an efficient and sustainable method to synthesize NH3. In this work, first-principles study was used to discuss the NRR process on B atom doped SbN monolayer. The adsorption of N2 on B-Sb17N18 and B-S18N17 was calculated including the adsorption energy, adsorption distance, and the charge density difference (CDD). Five different reaction pathways of NRR were taken into consideration and the stability of B-SbN was investigated. The results show that, because the energy of unoccupied orbital in sp3 hybridization of B atom is much lower than that in 2pz orbitals, the adsorption of N2 on B-Sb18N17 shows much larger adsorption energy (−1.01 eV with end-on pattern) compared to that of the adsorption on B-Sb17N18. For five different pathways, the 1, 2, and 4 pathways have a smaller limiting potential of about 0.52 V and the limiting step is: *N2 + H+ + e− → *NNH. The 3 and 5 pathways have a larger limiting potential of 0.57 V with hydrogenation step: *NHNH2 + H+ + e− → *NH2NH2. The B-Sb18N17 is structurally and thermally stable even at 500 K. Our theoretical prediction indicates that B atom substitutionally doped SbN monolayer can be a kind of high-performance metal-free NRR catalyst for NH3 synthetization, and the work provides attempts for designing and exploring 2D metal-free NRR catalysts.

Small Transition-Metal Mixed Clusters as Activators of the C-O Bond. FenCum-CO (n + m = 6): A Theoretical Approach.

Binding of carbon monoxide, CO, and its activation on the surface of the FenCumCO (n + m = 6) clusters are studied in this work. Using the BPW91/6-311 + G(2d) method, we have found that adsorption of the CO molecule on the surface of FenCum (n + m = 6) clusters is thermochemically favorable. Atop and bridge CO cluster coordinations appear for pure, Fe6 and Cu6, and mixed, Fe2Cu4 and Fe4Cu2, clusters. Threefold coordination takes place for Fe3Cu3-CO where the CO bond length, dCO, suffers a largest increase from 1.128 ± 0.014 Å for bare CO up to 1.21 Å. The CO stretching, νCO, as an indicator for the CO bond weakening is redshifted, from 2099 ± 4 cm-1 for isolated CO up to 1690 cm-1 for Fe3Cu3CO and 1678 cm-1 for Fe6CO. In addition, in Cu6CO, the strongest CO bond is slightly weakened as it has a bond length of 1.15 Å and a νCO of 2029 cm-1. There is a correlation between the CO bond weakening and the increase of CO coordination in FenCumCO, which in turns promotes the transference of charges from the metal core into the antibonding orbitals of CO. Substitution of up to three Cu atoms in Fe6 increases the adsorption energies and the activation of CO. Indeed, FenCum (n + m = 6) are promising clusters to catalyze CO dissociation, particularly Fe3Cu3, Fe5Cu, and Fe6, which have large CO bond lengths and CO adsorption energies. The Bader analysis of the electronic density indicates that FenCumCO species with threefold coordination show a rise in the C-O covalent character due to the less electronic polarization. They also show important M → CO charge transfer, which favors the weakening of the CO bond.

Ca coated B40 fullerene: A promising material for CO2 storage and separation

Density functional theory calculations were used to investigate the adsorption behavior of Ca coated B40 fullerene toward CO2 molecules. It was found that Ca atoms are unlikely to form clusters on B40. CO2 molecules can be effectively adsorbed on the Ca coated B40, as evidenced by large negative adsorption energies and significant charge transfer effects. Each Ca atom on B40 may adsorb four CO2, with an average adsorption energy of −0.54 eV which falls within the range proposed for an ideal CO2 adsorbent. Furthermore, Ca coated B40 exhibits high selectivity for CO2 from CO2/N2, CO2/H2, and CO2/CH4 gas mixtures.

First-principles Insights into Cu-Decorated GaN Monolayers for Sensing CO and HCHO in Dry-Type Transformers.

This work using first-principles theory studies the sensing properties of Cu-decorated GaN (Cu–GaN) monolayers as a promising candidate for the detection of CO and HCHO in dry-type transformers. The Cu dopant prefers to be trapped on the TN site of the GaN surface with an Eb of −1.13 eV. Chemisorption is identified for the two gas adsorption systems, given the large adsorption energy (Ead) of −1.35 and −1.09 eV. Caused by the chemisorption, the electronic property of the Cu–GaN monolayer is significantly deformed, narrowing its band gap of 0.548 eV to 0.00 eV, exhibiting metallic property, in two gas systems. Combined with the desirable recovery property for CO and HCHO desorption from the Cu–GaN surface, it could be proposed that the Cu–GaN monolayer is a promising gas sensor for toxic gas detection in dry-type transformers, so as to evaluate the operation status of the power system and guarantee safe working conditions for the maintenances.