Differences In Adsorption Energies Research Articles

Insights into the selectivity of metallic oxides for arsenic and phosphate from EXAFS and DFT calculations

Phosphate is the biggest competitor for arsenic removal. Nanoscale metal oxides (NMOs) are commonly used to treat arsenic-contaminated water, yet their selective adsorption mechanisms for arsenic and phosphate are poorly understood. We quantified the selectivity of iron oxide (Fe2O3), zinc oxide (ZnO), and titanium dioxide (TiO2) nanosheets for arsenic in systems containing arsenic and phosphate, and determined the interaction of phosphate and arsenate/arsenite on metal oxide surfaces through batch experiments, spectroscopic techniques, and DFT calculations. We found that Fe2O3, TiO2, and ZnO nanosheets exhibit selectivity for arsenate/arsenite in the presence of phosphate, with Fe2O3 the most selective, followed by TiO2 and ZnO. The bonding mechanism on these metallic oxide surfaces dominates the selectivity. The more stable inner-sphere complexes of arsenate on the surfaces of Fe2O3 (bidentate binuclear), TiO2 (bidentate binuclear), and ZnO nanosheets (tridentate trinuclear) contribute to their preference for arsenate over phosphate. This difference in arsenate selectivity can be reflected in the difference in adsorption energy, net electron transfer number, and M − O bond length of the most stable inner sphere complexes. Overall, our study elucidated the selective adsorption mechanisms of arsenate/arsenite on Fe2O3, TiO2, and ZnO surfaces and highlighted the need to consider the competition between arsenate and phosphate during their removal from contaminated water.

Surface Ti vacancy passivation of Ti3C2O2 MXene via transition metal atoms as high-performance potassium-ion batteries anodes

MXene exhibits tunable interlayer spacing, excellent conductivity and high redox activity, appearing to be ideal intercalated anodes of potassium ion battery. However, defects formed in the preparation process of this material seriously decrease the initial Coulombic efficiency (ICE) and diffusion rate. Herein, transition metals (TMs) passivation is employed to solve this problem based on DFT calculations. TMs filled in Ti vacancy (vTi) is figured out to form strong bonds with surround C and O atoms, which strength is positively-related with the outer electron numbers at d + s orbits of TMs. It enlarged the K adsorption energy difference (ΔEa) between cubic closest packing (ccp)- and hexagonal closest packing (hcp)-site, suggesting larger capacity than Ti3C2O2. ΔEa is revealed negatively linear-correlated with d-band center difference between TM and Ti element, then Fe and Mn would be excellent elements of passivation due to the smallest distance of d-band center to Ti. More importantly, TMs passivation obviously decreases the interaction between vTi and K+, lowering K+ diffusion barrier. This work provides new possibility of surface engineering for MXene performance modification beyond PIBs anodes.

Highly Sensitive and Selective Detection of Pharmaceuticals on Au/MIL-101(Cr) by SERS.

The detection of pharmaceuticals has been a matter of concern among scientists and health researchers in the past few decades. However, it is still difficult to realize the sensitivity and selectivity detection of pharmaceuticals with similar structures. Herein, the pharmaceutical molecules of 2-mercaptobenzimidazole (MBI) and 2-mercaptobenzothiazole (MBT) with so similar structures can be selectively detected by surface-enhanced Raman spectroscopy (SERS) taking advantage of the fingerprint identification on Au/MIL-101(Cr), with sensitive detection limits of 0.5 ng·mL-1 for MBI and 1 ng·mL-1 for MBT. MBI is selectively enriched by Au/MIL-101(Cr) from the mixture solution and detected by SERS below 30 ng·mL-1. MBI can also be selectively detected in the serum samples with a detection limit of 10 ng·mL-1. Density functional theory calculations combined with the SERS experiments explained that the high sensitivity and selectivity are caused by the intrinsic differences in Raman intensity and different adsorption energies from the pharmaceutical molecules adsorbed on Au/MIL-101(Cr), respectively. This study provides an effective way to enrich and detect pharmaceutical molecules with similar structures.

Solvent effect on adsorption of benzylidene oxindole to C20 nanocage: A DFT approach

AbstractIn this paper, one of the selective and potent inhibitors named (E)‐3‐benzylidene‐indoline‐2‐one (I), as against different receptor tyrosine kinase in metastasis, angiogenesis, and tumor growth, is inspected in the gas phase and in solution, at B3LYP/6‐311++G** and B3LYP/AUG‐cc‐pVTZ level of theory. A stimulating issue for this biologically active species is the effect of different media on its stability, structure, and energy gap in intermolecular [4 + 2] adsorption of I (as diene) to C20 (as dienophile) to yield (E)‐3‐benzylidene‐indoline‐2‐one[20]fullerene: Ia complex. In going from gas phase to C6H6, C2H4Cl2, EtOH, MeNO2, DMSO, and H2O solvents, individually, the optimization of complex (Ia) leads to the following: (1) The thermodynamic stability; the adsorption energy difference between liquid and gas phase (∆El–g) and dipole moment (μ) seem proportional to the dielectric constant (ε) of the scrutinized media. (2) The kinetic stability; energy difference (∆EL–H) between the frontier molecular orbitals; FMO in different media is altered in the opposite direction of ε. (3) Despite of popular belief that the endo isomer emerges thermodynamically more stable than its corresponding exo isomer, we suggest formation of kinetically more stable exo isomer because of π–π stacking among the benzyl ring and C20 nanocage. (4) The possibility of hetero [4 + 2] cycloaddition is anticipated by the lowest energy barrier of 3.8 kcal/mol probed for exo transition state (TS) in gas phase, while the highest energy barrier of 7.9 kcal/mol corresponds to the endo TS in water. (5) Due to lack of the repulsion type interaction, the exo [4 + 2] cycloaddition of unstable C20 fullerene with the scrutinized oxindole can be carried out thermally at r.t. and currently hold responsible for the origin of stereoselectivity.

Building Up an “Elemental Property—Adsorption Energy Descriptor—Decomposition Barrier” Three‐Tier Model for Screening Biatom Catalysts in Sodium–Sulfur Batteries

AbstractDeveloping highly efficient catalysts for the Na2S redox process and sodium polysulfide anchoring is becoming increasingly important for high‐performance sodium–sulfur (Na–S) batteries. The recently emerged graphene‐supported biatom catalysts (G‐BACs) exhibit great potential for providing high activity in both discharging and charging processes. However, the fast screening of promising G‐BACs for Na–S batteries is hindered by the formidable computational cost for calculating Na2S decomposition barriers (Eb). Herein, this work develops an “elemental property—adsorption energy descriptor—decomposition barrier” three‐tier model to accelerate this process and elucidates the origin of catalytic activity. It is found that Eb during the charging process is linearly correlated with the adsorption energy difference between the initial and final states of Na2S decomposition (Ediff) for both homonuclear and heteronuclear transition metal G‐BACs. This work further correlates Ediff with intrinsic properties of metal elements by machine learning approaches and unravels the most significant elemental feature to be the outer electron number. This work not only accelerates the design of highly efficient G‐BACs in Na–S batteries based on the structure–activity relationship, but also provides a feasible strategy for the fast screening of catalysts for other electrochemical reactions for potential experimental design.

Exceptional Sorption of Heavy Metals from Natural Water by Halloysite Particles: A New Prospect of Highly Efficient Water Remediation.

Halloysite particles, with their unique multilayer nanostructure, are demonstrated here as highly efficient and readily available sorbent of heavy metals that can be easily scaled up and used in large-scale water remediation facilities. The various methods of raw material purification were applied, and their effects were verified using techniques such as BET isotherm (determination of specific surface area and size of pores), XRF analysis (composition), and SEM imaging (determination of morphology). A series of adsorption experiments for aqueous solutions of metal ions (i.e., lead, cadmium) were carried out to quantify the sorption capacity of halloysite particles for selected heavy metals. The ability of adequately activated halloysite to efficiently remove heavy metal ions from water solutions was confirmed. The value of the zeta potential of raw and purified halloysite particles in water was determined. This enables us to understand its importance for the sorption of positively charged ions (metal, organics) at various pH values. The adsorption process conducted in the pH range of 6.0-6.5 showed significant improvement compared to the acidic conditions (pH value 3.0-3.5) and resulted in a high sorption capacity of lead ions-above 24.3 mg/g for the sulphuric acid-treated sample. The atomic scale ab initio calculations revealed a significant difference in adsorption energy between the external siloxane surface and cross-sectional interlayer surface, resulting in pronounced adsorption anisotropy. A low energy barrier was calculated for the interlayer migration of heavy metals into the halloysite interior, facilitating access to the active sites in these regions, thus significantly increasing the sorption capacity and kinetics. DFT (density functional theory) calculations supporting this study allowed for predicting the sorption potential of pure halloysite structure towards heavy metals. To confront it with experimental results, it was crucial to determine proper purification conditions to obtain such a developed structure from the mineral ore. The results show a massive increase in the BET area and confirm a high sorption potential of modified halloysite towards heavy metals.

Phosphoric acid resistance PtCu/C oxygen reduction reaction electrocatalyst for HT-PEMFCs: A theoretical and experimental study

In high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), dissociative H3PO4 in cathode will block the active sites of Pt-based electrocatalyst, which thus failure to catalyze the oxygen reduction reaction (ORR). Therefore, the electrocatalysts for the ORR in HT-PEMFCs with high resistance to H3PO4 poisoning are significantly important. Due to the similar bonding structure between HxPO43-x/O2 and Pt (Pt-O), the design of catalysts which could selectively reduce the adsorption energy of the H3PO4 is urgently needed. In this work, we screen proper H3PO4 resistance electrocatalysts through theoretical calculation based on the adsorption energy difference between HxPO43-x and O2 as an evaluation criterion. Then, we prepared a series of PtxCu catalysts based on the theoretical calculation results and further studied the structure-performance relationship of phosphoric acid-resistant catalysts through combining physical property characterization and electrochemical tests including half-cell and single-cell. The mass activity of Pt2Cu/C is 0.51 A/mgPt, exceeding the DOE's 2020 target of 0.44 A/mgPt. After add 0.1 M H3PO4 into the HClO4 electrolyte, the half-wave potential (E1/2) of Pt2Cu/C is only negatively shifted by 47 mV, much lower than 90 mV of TKK Pt/C. Furthermore, the HT-PEMFC with Pt2Cu/C in the cathode shows a peak power density of 383.4 mW/cm2, which surpasses that of TKK Pt/C for 231.0 mW/cm2. Our strategy of screening catalysts based on the adsorption energy difference study and further verified by experimental methods provides a promising strategy for the design of practical electrocatalyst in the cathode of HT-PEMFCs.

Investigation on adsorption of sodium fluoro-aluminates on graphite by density functional theory

The carbonous materials have been widely used as electrodes in the current aluminum industry. Cathode wear has been an unavoidable problem and limits the lifetime of electrolysis cells in aluminum production, which is mainly due to the reaction between molten cryolite salts and the graphite surface, formation of an aluminum carbide layer on the surface of the cathode, sodium penetration, and abrasion of molten salts. However, the mechanism of cathode wear is still not fully understood, and not clarified at the atom level. In this paper, density functional theory based calculations were performed to investigate the reactivity properties between fluoro-aluminates and graphite surfaces. The adsorption energy and optimized structures of three typical fluoro-aluminates on various sites were obtained, indicating that chemical adsorption has occurred, and Na2AlF5 was easier than Na3AlF6 and NaAlF4 to adsorb on the graphite surface. The adsorption sites only cause a slight difference in adsorption energy since the size of fluoro-aluminates is larger than the distance between various sites. Moreover, the charge density differences, density of states, and partial charge density were calculated to illustrate the electron transfer between fluoro-aluminates and the graphite cathode. During the adsorption of fluoro-aluminates on the graphite surface, electrons would transfer from sodium to the graphite cathode. Meanwhile, the electrons of carbons are attracted by fluorine atoms. However, there is no electrons transfer directly between the aluminum atom and the graphite surface.

Volatile organic compounds gas molecule adsorption on Fe-MoS2 monolayer: The first-principles study

In this paper, the adsorption properties of Toxic volatile organic compounds gas molecules (C6H6, C2H4O, C2H3Cl and CH3CHO) on MoS2 and Fe - MoS2(Fe-MoS2) were investigated using a first principles approach. we reported that Fe doped monolayer MoS2 nanomaterials were a promising approach to improve their gas sensing performance. The adsorptions of Toxic volatile organic compounds gas molecules (C6H6, C2H4O, C2H3Cl and CH3CHO) gas molecule on Fe-MoS2 were studied in terms of adsorption energy, charge transfers, band structures, and charge density differences. The result suggested that the adsorption of VOCs gas molecule on the Fe-MoS2 monolayer was energetically favorable, which gives rise to the most stable configurations. Besides, the VOCs gas molecule was physisorbed on the monolayer surface due to the weak interaction between them and Fe-MoS2 monolayer. Most notably, the Fe-MoS2 monolayer might be a great candidate for low-cost, highly active, and stable catalysts and gas sensors, providing an avenue to facilitate the design of highly active MoS2-based two-dimensional gas sensor.

Facet-dependent electrocatalytic oxidation activity of Co3O4 nanocrystals for 5-hydroxymethylfurfural

Metal oxide catalysts’ performance depends on the surface arrangement and coordination of metal cations and oxygen anions on the exposed facets. The primary factor is the difference in HMF adsorption energy on various crystal facets.

Ternary transition metal organic frameworks (MOFs) CuZn-MIL101 (Fe) for peroxymonosulfate activation to degradation of 2-methyl-4-chlorophenoxyacetic acid (MCPA): A non-radical pathway dominated by singlet oxygen

In this study, ternary CuZn-MIL101(Fe) MOFs were prepared by introducing Cu and Zn ions into MIL-101(Fe) to obtain catalysts with excellent peroxymonosulfate (PMS) activation properties. The comprehensive characterization analysis revealed that although the adsorption performance of CuZn-MIL101(Fe) decreased, the PMS activation performance was significantly improved and complete degradation of MCPA was reached in 20 min. Calculation of the specific rate constants (kSA) yielded that the intrinsic activity of CuZn-MIL101(Fe) for PMS was 34 and 37 times higher than that of CuZn0.25-MIL101(Fe) and Cu0.25Zn-MIL101(Fe), respectively. The quenching experiments combined with electron paramagnetic resonance (EPR) spectroscopy verified the composition of the active substances in the system, whose contributions were in the order of O21 > ·OH > SO4⋅− > O2⋅. Using PMSO as a probe, an important role of high-valent iron was found in the system. The HOMO-LUMO gap of MCPA was calculated to be 0.205 eV by density functional theory (DFT), and the difference in adsorption energy of MCPA when adsorbing different radicals was investigated. The intermediate products were obtained by GC-MS and analyzed for toxicity, and the mechanism of singlet oxygen-dominated degradation of MCPA was proposed, which laid the foundation for the subsequent in-depth study of phenoxyacetic acid-based herbicides.

The chemical reaction of thioindole and [20] fullerene and the use of DFT to estimate some quantum chemical descriptors

In this study, the solvent effects are probed on the chemical reaction of the (E)-3-thiophene-2-yl-indoline-2-thione (I) and [20] fullerene, and the resulted complex (Ia ) via the density functional theory (DFT). To characterize the synchronicity of the reaction and its correlation with activation energy, we estimated the energy barrier of transition states (E TS1 ≠ and E TS2 ≠) in the used solvents. The highest E TS1 ≠ and E TS2 ≠ value are found in water solvent, whereas the lowest E TS1 ≠ and E TS2 ≠ value are considered in the gas phase. Formation of the TS2 appears energetically less favorable due to the non-bonding electrostatic repulsion among the sulfur heteroatoms and C20 , also the π–stacking between the thiophene ring and nanocage, which affects the stability of the TSs. The most thermodynamic stability, the adsorption energy difference among liquid phase and gas phase (ΔE l-g = E l − E g), and the most polarity (µ) belongs to stabilizing effect of water solvent on Ia , whereas the lowest thermodynamic stability, the lowest released ΔE l-g and the least polarity belongs to optimization of Ia in the gas phase. This stabilizing effect is attributed to the possibility of hydrogen bonding and dipole–dipole interaction in the water. The n→π* donation of N–C═S leads to a stronger interaction between sulfur heteroatom of I and fullerene. In contrast to the previous report on the produced thio-oxindoles in organic solvents, toluene was found to be the best solvent in terms of the highest yield and the shortest reaction time, in this case, adsorption takes place in water with no catalyst addition. Here, we have focused on chemical reaction of I and C20 to produce Ia complex via the optimized TSs in the gas phase, toluene, dichloromethane, methanol, acetonitrile, dimethyl sulfoxide and water, using DFT approach.

AP-XPS Study of Ethanol Adsorption on Rutile TiO2(110)

The photoactivity of rutile TiO2(110) renders its surfaces of particular interest for the study of surface reactions. In particular, rutile TiO2(110) surfaces are active for hydrogen production, both via the water splitting process and via ethanol degradation under ultraviolet illumination. The selective photocatalytic dehydrogenation of rutile TiO2(110) is not fully understood yet, and an important question in this context is how ethanol adsorbs onto the rutile TiO2(110) surface under ambient conditions. Here, we present the first in situ experimental study on the absorption of ethanol on rutile TiO2(110) at room temperature and near-ambient conditions. The surface sensitivity of synchrotron-based ambient pressure X-ray photoelectron spectroscopy allows for an in-depth analysis of the surface species (molecular ethanol and ethoxies) and their coverage as well as an estimation of the energy difference between the two species. Through modeling of the O 1s core level and comparison to experimental results we show that both molecular and dissociative adsorption of ethanol occurs. The difference in adsorption energy range calculated from modeling of the O 1s core level was 0.018–0.033 eV, with dissociative adsorption the most energetically favorable. The difference in adsorption energy is almost an order of magnitude lower than previous estimations from theoretical calculations. In addition, we show that at room temperature a multilayer is formed with increasing pressure of ethanol.

Insights into the Effect of the Adsorption Preference of Additives on the Anisotropic Growth of ZSM-5 Zeolite.

Zeolite morphology plays a crucial role in affecting catalytic performance, while is persistently challenging to tailor through crystal anisotropic growth. It has been recognized that specific additives can be introduced into the synthesis of zeolites to achieve anisotropic growth, however their role and the underlying mechanism are not well understood. Herein, the effect of eight specific additives on the anisotropic growth of the ZSM-5 zeolite is unveiled within the framework of crystallization engineering. Either an inhibition effect or a promotion effect is revealed for each additive according to the crystallization kinetics. The adsorption preference of typical additives on different surfaces was demonstrated by total internal reflection fluorescence microscopy (TIRFM) and transmission X-ray microscopy (TXM) together with 3D reconstruction. The calculated adsorption energy difference between MFI [100]/[101] and [010] surfaces was proposed as a key descriptor to estimate the possible morphology induced by additive. ZSM-5 zeolites varying from sphere-like, plate-like to noodle-like morphology could be synthesized by employing specific additives with increasing adsorption strength difference on distinct surfaces.

Accurate Determination of Adsorption-Energy Differences of Metalloporphyrins on Rutile TiO2(110) 1 × 1.

Understanding the adsorption of organic molecules on surfaces is of essential importance for many applications. Adsorption energies are typically measured using temperature-programmed desorption. However, for large organic molecules, often only desorption of the multilayers is possible, while the bottom monolayer in direct contact to the surface cannot be desorbed without decomposition. Nevertheless, the adsorption energies of these directly adsorbed molecules are the ones of the most interest. We use a layer-exchange process investigated with X-ray photoelectron spectroscopy to compare the relative adsorption energies of several metalated tetraphenylporphyrins on rutile TiO2(110) 1 × 1. We deposit a mixture of two different molecules, one on top of the other, and slowly anneal above their multilayer desorption temperature. During the slow heating, the molecules begin to diffuse between the layers and the molecules with the stronger interaction with the surface displace the weaker-interacting molecules from the surface and push them into the multilayer. The multilayers eventually desorb, leaving behind a monolayer of strongly interacting molecules. From the ratio of the two different porphyrin molecules in the residual monolayer and the desorbed multilayer, we can calculate the equilibrium constant of the layer-exchange process and thereby the difference in adsorption energy between the two different porphyrin molecules.

Investigation of structural properties of Mg-doped twisted bilayer graphene for phosphine gas detection

ABSTRACT This study has investigated the adsorption of phosphine toxic gas molecule on monolayer graphene, bilayer graphene and twisted bilayer graphene with, and without Magnesium impurity. The results of absorption energy studies using density functional theory (DFT) showed that bilayer graphene provides better adsorption than monolayer graphene and a difference in adsorption energy will be observed for twisted bilayer graphene with a rotation angle of 21.78°. By adding Mg impurity to the configurations, the sensitivity, and working temperature of the twisted bilayer graphene with Mg impurity increase compared to twisted bilayer graphene. Also, working temperature, and value of adsorption energy were calculated for bilayer graphene with Mg impurity less than Mg-doped twisted bilayer graphene, and monolayer graphene with Mg impurity.

Anion-kinetics-selective graphene anode and cation-energy-selective MXene cathode for high-performance capacitive deionization

Capacitive deionization (CDI) is one of the most promising energy-efficient technologies for water desalination, however its industrial translation is slow and impeded by limited electrosorption capacity, slow electrosorption rate and poor cycling stability. Herein we address the above challenges by developing and validating a new concept of unimpeded and selective full-cell anion-cation separation using custom-designed anion-kinetics-selective anode and cation-energy-selective cathode. Nanoporous graphene anode enables the selective anion kinetics, while cation selectivity on the functionalized MXene cathode is due to the difference in ion adsorption energy. These mechanisms are validated by electrochemical quartz crystal microbalance measurements. The finely-tuned balance between ion transport and adsorption causes unimpeded ion diffusion, leading to the higher electrosorption rates. These effects are guided by the atomistic and quantum chemistry simulations, and also confirmed experimentally by tuning the pore size of graphene anode and the functionalization of MXene cathode. The fabricated asymmetric CDI cell exhibits superior electrosorption capacity of 49 mg g−1 and high electrosorption rate of 2.92 mg g−1 min−1 in 5000 mg L−1 NaCl solution as well as excellent cycling stability (100 cycles), which are among the best of the current state-of-the-art CDI studies. These results demonstrate the design of advanced electrode materials for the effective control of ion kinetics and energies to achieve selective ion transport, thus providing new insights for a broader range of energy-related applications.

The role of copper ion and soluble starch used as a combined depressant in the flotation separation of fluorite from calcite: New insights on the application of modified starch in mineral processing

• Cu 2+ and soluble starch (SS) together enhance fluorite/calcite flotation separation. • The mechanism was systematically studied from chemical and atomic perspectives. • Cu SS complex interacts strongly with calcite but only weakly with fluorite . • Metal-ion modified starches are flotation reagents with great potential. The flotation separation of fluorite and calcite poses a long-standing challenge in the mineral processing industry because of their similar physicochemical characteristics. In this study, the effects of Cu 2+ and soluble starch (SS) in the separation of fluorite from calcite by flotation, and the mechanisms behind these effects, were investigated using micro-flotation experiments, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), time of flight secondary ion mass spectrometry (ToF-SIMS) and density functional theory (DFT). The micro-flotation experiments show that the combination of Cu 2+ and SS exhibits a stronger selective depression effect on calcite than that produced by SS alone; in contrast, the effect on fluorite flotation is relatively small. The XPS, FT-IR and ToF-SIMS analyses show that Cu 2+ can react with SS to form a Cu SS complex, which has better selectivity, resulting in the difference in flotation performance between fluorite and calcite. DFT results show that the SS and the Cu-SS complex form different chemical bonds during their interactions with the mineral surfaces: Ca O bond and H F bonds are formed when SS interacts with the fluorite surface, and Ca O and hydrogen bonds are formed when SS interacts with the calcite surface. A Ca Cu bond is formed when the Cu SS complex interacts with the fluorite surface, but both Cu O and Ca Cu bonds are formed when the Cu SS complex interacts with the calcite surface. This causes differences in adsorption energy. The adsorption energies of the interactions between SS or Cu SS complex and the surfaces of fluorite and calcite are ranked as: calcite + Cu SS complex > calcite + SS > fluorite + SS > fluorite + Cu SS complex.

Bidentate ligand modification strategy on supported Ni nanoparticles for photocatalytic selective hydrogenation of alkynes

The design of selective and stable non-precious metal catalysts for hydrogenation of alkyne is highly desirable. In this study, L-lysine modification strategy is applied to support Ni nanoparticles, which greatly improves the stability and photocatalytic performance in the hydrogenation of phenylacetylene to styrene. The robust stability is attributed to that both amino and carboxyl groups of L-lysine can function simultaneously as the anchor, much stronger than a single group, to strongly interact with metallic Ni via N and O coordination. The high selectivity to styrene is due to that L-lysine modification results in a larger adsorption energy difference between styrene and phenylacetylene on the surface of Ni, therefore phenylacetylene is preferentially adsorbed on Ni surface. This protocol shows that the modulation of interaction between ligands and Ni is favorable to design stable, active and selective catalysts for hydrogenation of alkynes.

Molecular-Level Insights into the Notorious CO Poisoning of Platinum Catalyst.

Carbon monoxide (CO) is notorious for its strong adsorption to poison platinum group metal catalysts in the chemical industry. Here, we conceptually distinguish and quantify the effects of the occupancy and energy of d electrons, emerging as the two vital factors in d-band theory, for CO poisoning of Pt nanocatalysts. The stepwise defunctionalization of carbon support is adopted to fine-tune the 5d electronic structure of supported Pt nanoparticles. Excluding other promotional mechanisms, the increase of Pt 5d band energy strengthens the competitive adsorption of hydrogen against CO for the preferential oxidation of CO, affording the scaling relationship between Pt 5d band energy and CO/H2 adsorption energy difference. The decrease of Pt 5d band occupancy lowers CO site coverage to promote its association with oxygen for the total oxidation of CO, giving the scaling relationship between Pt 5d occupancy and activation energy. The above insights outline a molecular-level understanding of CO poisoning.