Lower Adsorption Energy Research Articles

Atomic S, H and C adsorption on MnO(001) surface and the interaction between H and LaCrO3(001) surface: A computational analysis

S poisoning and C deposition are key factors to cause performance degradation of solid oxide fuel cells (SOFC) anodes. The adsorptions of atomic S, H and C on MnO(001) surface and atomic H on LaCrO3(001) surface are systematically investigated using density functional theory (DFT) calculations. The analysis of surface relaxation shows that surface Mn ion slightly moves toward the slab center and surface O ion moves outward on MnO(001) surface. According to the result of adsorption energy, it can be inferred that the MnO weakens the adsorption of atomic S with lower adsorption energies compared to LaCrO3 surface. In addition, the findings show that the preferred site for atomic H adsorption is O site, with the adsorption energy of －1.361 eV, which results in the formation of –OH surface species. Compared to O sites on LaCrO3(001) surface, the atomic H is found to interact weakly with the La and Cr sites. The distances and charges transfer between adsorbate and substrate have also been analyzed. The obtained results are expected to provide some fundamental information for future research on mechanism of S poisoning and C deposition on SOFC anodes.

Exploring curcumin interaction with PLGA nanoparticles via various functional groups: A dispersion-corrected density functional theory and molecular dynamics simulation approach

Density functional theory (DFT)-D3 dispersion corrections and molecular dynamic (MD) techniques were used to research how curcumin (CUR) and poly (lactic-co-glycolic acid) (PLGA) interact in the water phase. Relaxation based on machine learning (ML) algorithms was used to identify the state configuration that was the most stable. The electronic, optical, and infrared (IR) vibrational properties of the studied configurations were then computed. The findings show that since PLGA nanoparticle can transport CUR via chemical interactions, the binding energy of CUR through carbonyl group to PLGA is about −1.092 eV (complex A). The theoretical IR spectrum supports the observation that the functional groups of CUR interacting with PLGA undergo changes, which is consistent with the experimental data. Hence, the Bader charge analysis indicates a charge of about 0.14 (complex A) and 0.17 (complex B) |e| transferred from the PLGA to CUR. The charges in CUR exhibit strong charge transfer to the PLGA structure. The calculated results of the CUR-PLGA complex match the main peak in the 500–580 nm range observed in experiments, and the stable optimal optical absorption diagram aligns with the reported spectra. The total density of states (TDOS) of the studied configurations shows that CUR is having an impact on the HOMO and LUMO levels. The PLGA nanoparticle demonstrates a higher sensitivity (86%) towards the presence of CUR in complex D compared to complex B (67%), which can be attributed to the change in the energy gap. This low adsorption energy and high sensitivity suggest that the PLGA nanoparticle indicates its potential to serve as both a carrier and a sensor for detecting CUR in the water phase.

P2-type low-cost and moisture-stable cathode for sodium-ion batteries

Mn-based P2-type oxides are considered as promising cathodes for Na-ion batteries; however, they face significant challenges, including structural degradation when charged at high cutoff voltages and structural changes upon storing in a humid atmosphere. In response to these issues, we have designed an oxide with co-doping of Cu and Al which can balance both cost and structural stability. The redox reaction of Cu2+/3+ can provide certain charge compensation, and the introduction of Al can further suppress the Jahn-Teller effect of Mn, thereby achieving superior long-term cycling performance. The ex-situ XRD testing indicates that Cu/Al co-doping can effectively suppress the phase transition of P2-O2 at high voltage, thereby explaining the improvement in electrochemical performance. DFT calculations reveal a high chemical tolerance to moisture, with lower adsorption energy for H2O compared to pure Na0.67Cu0.25Mn0.75O2. A representative Na0.67Cu0.20Al0.05Mn0.75O2 cathode demonstrates impressive reversible capacities of 148.7 mAh/g at 0.2 C, along with a remarkable capacity retention of 79.1% (2 C, 500 cycles).

Oxygen Defects Containing TiN Films for the Hydrogen Evolution Reaction: A Robust Thin-Film Electrocatalyst with Outstanding Performance.

Density functional theory (DFT) calculations of hydrogen adsorption on titanium nitride had previously shown that hydrogen may adsorb on both titanium and nitrogen sites with a moderate adsorption energy. Further, the diffusion barrier was also found to be low. These findings may qualify TiN, a versatile multifunctional material with electronic conductivity, as an electrode material for the hydrogen evolution reaction (HER). This was the main impetus of this study, which aims to experimentally and theoretically investigate the electrocatalytic properties of TiN layers that were processed on a Ti substrate using reactive ion sputtering. The properties are discussed, focusing on the role of oxygen defects introduced during the sputtering process on the HER. Based on DFT calculations, it is shown that these oxygen defects alter the electronic environment of the Ti atoms, which entails a low hydrogen adsorption energy in the range of -0.1 eV; this leads to HER performances that match those of Pt-NPs in acidic media. When a few nanometer-thick layers of Pd-NPs are sputtered on top of the TiN layer, the performance is drastically reduced. This is interpreted in terms of oxygen defects being scavenged by the Pd-NPs near the surface, which is thought to reduce the hydrogen adsorption sites.

Hydrogen Storage Capacity of Cobalt Cluster Ions.

The adsorption of H2 on gas-phase Con± (n = 5-12) clusters at 300 K and the desorption of H2 from ConHm± upon heating were studied experimentally by combining thermal desorption spectrometry and mass spectrometry to elucidate the hydrogen storage property of the Co clusters. Hydrogen atoms adsorbed well on Con+ (n = 5, 10-12) and Con- (n = 5-12) at 300 K to form ConHm±. The atomic ratios, m/n, for ConHm- (0.9-1.4) were higher than those for ConHm+ (0.2-1.1). According to density functional theory (DFT) calculations, the first few H2 molecules had a tendency to dissociatively adsorb onto the Co clusters. Further, the bonding nature of the H atoms was ionic, similar to the H atoms in the metallic hydrides. In contrast, H2, adsorbed molecularly, was explained in terms of σ complex formation. H2 molecules were desorbed from the clusters upon heating. The temperature dependences showed that ConHm- released H2 at a higher temperature (700-800 K) than ConHm+ (600-700 K), suggesting that Con- should have a higher affinity to hydrogen than Con+. The desorption temperatures were lower than those of VnHm+, which was consistent with the fact that the adsorption energies of H2 were lower for the Co clusters than those for the V clusters. The low adsorption energies were ascribed to their large highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps in the Co clusters.

Analysis of the adsorption and fixation process of ammonium nitrogen in arable soil by biochar based on molecular dynamics simulation

The ammonia nitrogen in arable land soil is susceptible to environmental and anthropogenic influences, leading to nutrient loss. This study utilized indoor soil column leaching experiments, combined with adsorption mathematical models, traditional characterization methods, and molecular dynamics simulation methods, to analyze the effects of biochar on changes in ammonium ions in different soil layers and leachate of arable land soil. The study found that applying biochar at a ratio of 10 % to arable land soil could effectively increase the ammonium ion content in the 0–10 cm soil layer by 1.57–2.36 times and reduce loss by 44.83–72.27 %. The adsorption and fixation process of biochar is controlled by electrostatic attraction and ion exchange processes. Interactions between molecules, electrostatic forces, and system internal energy also have certain effects on the process. Near the structure of C6H12O6, there are low-energy adsorption sites for ammonium ions, which can provide the energy required for electrostatic attraction. Structures such as C5H10O5, C-S-H, C-SO3, and C4H7NO4 respectively play roles in physical adsorption or chemical adsorption through displacement reactions, electron exchange, and other forms. The adsorption free energy is −394,590.84 kcal/mol, indicating stable adsorption and a process that tends to interact with the biochar surface. This study addresses issues such as the easy loss of ammonia nitrogen in arable land soil and the unclear adsorption mechanism of biochar on ammonium ions, providing a theoretical basis for the field of environmental science.

DFT studies of the structural and electronic properties of PdGe n (n = 1–11) clusters and adsorption capacity for some gas molecules

Density functional theory calculations have been employed for the theoretical studies of the geometric structures and electronic characteristics of PdGe n (n = 1−11) clusters. An analysis of the second- order energy differences indicates that PdGe7 and PdGe10 clusters possess superior thermodynamic stability. PdGe10 displays the highest chemical stability and the lowest chemical activity, due to its largest energy gap value (E g). Vertical ionization potential and vertical electron affinity exhibit the decreasing and increasing trends, respectively, with the increase of the number n of Ge atoms. PdGe10 presents the highest electronegativity among these clusters. The analysis on the adsorption properties of PdGe n (n = 7,10) clusters for gas molecules (e.g. CO, NO, NO2, NH3, SO2 and H2S) yields the adsorption structures, adsorption energies, Mulliken charge transfer and the changes in the electronic properties. All the listed gas molecules chemically adsorb onto PdGe7. PdGe10 has a better adsorption performance for NO2, while its adsorption ability for CO is poorer. The potentiality of PdGe n (n = 7, 10) clusters as gas sensors is also evaluated and reveals that NO adsorption significantly affects the electronic properties, especially conductivity, of the systems. PdGe10 has an appropriate NO adsorption capacity and significant charge transfer, with the adsorption energy of −0.278 eV and the recovery time of about 10−9s, indicating its fast response and hence good potentiality as the NO sensor. In contrast, PdGe7 has a higher adsorption capability towards NO with a lower adsorption energy of −1.16 eV, leading to the difficulty in desorption and a longer recovery time of over 12 h.

Efficacious destruction of typical aromatic hydrocarbons over CoMn/Ni foam monolithic catalysts with boosted activity and water resistance

Developing cost-effective monolith catalyst with superior low-temperature activity is critical for oxidative efficacious removal of industrial volatile organic compounds (VOCs). However, the complexity of the industrial flue gas conditions demands the need for high moisture tolerance, which is challenging. Herein, CoMn–Metal Organic Framework (CoMn–MOF) was in situ grown on Ni foam (NiF) at room temperature to synthesize the cost-effective monolith catalyst. The optimized catalyst, Co1Mn1/NiF, exhibited excellent performance in toluene oxidation (T90 = 239 °C) due to the substitution of manganese into the cobalt lattice. This substitution weakened the Co–O bond strength, creating more oxygen vacancies and increasing the active oxygen species content. Additionally, experimentally and computationally evidence revealed that the mutual inhibiting effect of three typical aromatic hydrocarbons (benzene, toluene and m–xylene) over the Co1Mn1/NiF catalyst was attributed to the competitive adsorption occurring on the active site. Furthermore, the Co1Mn1/NiF catalyst also presents outstanding water resistance, particularly at a concentration of 3 vol%, where the activity is even enhanced. This was attributed to the lower water adsorption and dissociation energy derived from the interaction between the bimetals. Results demonstrate that the dissociation of water vapor enables more reactive oxygen species to participate in the reaction which reduces the formation of intermediates and facilitates the reaction. This investigation provides new insights into the preparation of oxygen vacancy–rich monolith catalysts with high water resistance for practical applications.

Investigate the effect of C coating on the wetting and reaction mechanism of Sc2W3O12 and AgCuTi filler

Mitigating the interface reaction between negative thermal expansion materials and filler metals is crucial for enhancing the functionality of negative thermal expansion materials. However, the general approach to mitigate interface reaction, such as minimizing both reaction time and temperature, will result in insufficient metallurgical reactions necessary to establish reliable connections during the brazing process. Through wetting process analysis and first-principles calculations, the effect of C coating on the wetting and reaction mechanism of Sc2W3O12 and AgCuTi filler is revealed. The wetting experiment indicates that the C coating not only improves the wettability but also mitigates the interface reaction. According to the interfacial microstructure, 18 kinds of Ti/Ti3O5 (001) and 3 kinds of Ti/TiC (100) adsorption systems are constructed to calculate the adsorption characteristics. According to the calculations, the Ti/TiC (100) system has lower adsorption energy than Ti/Ti3O5 (001) system, indicating that Ti atoms are more easily adsorbed on the TiC surface. The charge density difference contour shows that the charge repulsion on the TiC surface restricts the entry of Ti atoms. This work provides new insights into the mechanism of how the C coating to reduce interfacial consumption of the negative thermal expansion materials.

Ordered PtNiTiZrHf nanoparticles on carbon nanotubes catalyze hydrogen evolution reaction with high activity and durability

With the scarcity of the earth's natural resources, hydrogen production from electrolyzing water is seen as an alternative energy source. Although platinum (Pt) is an advanced catalyst for hydrogen evolution reaction (HER), its application is limited by high cost and limited electrocatalytic performance. In this article, the five-element alloy nanoparticles are successfully synthesized on carbon nanotubes (CNT) by employing liquid-phase reduction and gas-phase sintering to reduce Pt utilization and improve catalytic performance. For comparison, a series of ordered and disordered (PtNi)x(TiZrHf)100-x/CNT catalysts are obtained. Results show that the ordered samples have more excellent HER catalytic performance and stability than disordered samples in 0.5 M H2SO4 and 1 M KOH electrolytes. In particular, when the electrolyte is acidic, the overpotentials of ordered (PtNi)55(TiZrHf)45/CNT at 10 and 100 mA cm−2 are 11 and 52 mV, with low Tafel slope of 37.73 mV dec−1. At 10 mA cm−2, the stabilization time can reach 58 h, which is much better than commercial Pt/C (20 wt.%). Density functional theory (DFT) calculation shows that ordered (PtNi)55(TiZrHf)45/CNT has lower hydrogen adsorption energy and activated water adsorption energy than disordered one, indicating better performance in both acidic and alkaline electrolytes. It is mainly attributed to the electronic coupling effect after ordering that makes the overall D-band center decrease. This work presents a cost-effective approach to optimize the structural design for acid-base HER electrocatalysts.

One-stone, two birds: One step regeneration of discarded copper foil in zinc battery for dendrite-free lithium deposition current collector

The ever-growing requirement for electrochemical energy storage has exacerbated the production of spent batteries, and the recycling of valuable battery components has recently received a remarkable attention. Among all battery components, copper foil is widely utilized as a current collector for stable zinc platting and stripping in zinc metal batteries (ZMBs) due to the perfect lattice matching of between metal copper and zinc, which is accompanied by the formation of multiple copper-zinc alloy components during the cycling process. Herein, a novel “two birds with one-stone” strategy through a one simple heat treatment step to revive the discarded copper foil in zinc metal battery is reported to further obtain a lithiophilic current collector (CuxZny-Cu) with multiple copper-zinc alloy components on the surface of the discarded copper foil. Such revived CuxZny-Cu current collector greatly reduces the lithium nucleation overpotential and realizes uniform lithium deposition and further inhibits lithium dendrites growth. The formed multiple CuxZny alloy phases on the surface of discarded copper foil exhibit a low Li nucleation overpotential of only 15 mV at 0.5 mA cm−2 for the first cycle. Moreover, such a CuxZny-Cu current collector could achieve stable cycle for 220 cycles at 0.5 mA cm−2 and 110 cycles at 1 mA cm−2 with a Li plating capacity of 1 mAh cm−2. Theoretical calculations indicate that, compared with pure Cu foil, the formed multiple alloy components of CuZn5, CuZn8, Cu0.61Zn0.39 and CuZn have low adsorption energy of −2.17, −2.55, −2.16 and −2.35 eV with lithium atoms, respectively, which result in reduced lithium nucleation overpotential. The full cell composed of CuxZny alloy current collector with deposition of 5 mAh cm−2 metal Li anode coupled with LiFePO4 (LFP) cathode exhibits a reversible capacity of 125.6 mAh/g after 110 cycles at a current of 0.5 C with capacity retention of 85.1 %. This work proposed a promising strategy to regenerate the discarded copper foil in rechargeable batteries.

Regulation of the d-band center of metal–organic frameworks for energy-saving hydrogen generation coupled with selective glycerol oxidation

The hybrid electrolyzer coupled glycerol oxidation (GOR) with hydrogen evolution reaction (HER) is fascinating to simultaneously generate H2 and high value-added chemicals with low energy input, yet facing a challenge. Herein, Cu-based metal-organic frameworks (Cu-MOFs) are reported as model catalysts for both HER and GOR through doping of atomically dispersed precious and nonprecious metals. Remarkably, the HER activity of Ru-doped Cu-MOF outperformed a Pt/C catalyst, with its Faradaic efficiency for formate formation at 90% at a low potential of 1.40 V. Furthermore, the hybrid electrolyzer only needed 1.36 V to achieve 10 mA cm-2, 340 mV lower than that for splitting pure water. Theoretical calculations demonstrated that electronic interactions between the host and guest (doped) metals shifted downward the d-band centers (εd) of MOFs. This consequently lowered water adsorption and dissociation energy barriers and optimized hydrogen adsorption energy, leading to significantly enhanced HER activities. Meanwhile, the downshift of εd centers reduced energy barriers for rate-limiting step and the formation energy of OH*, synergistically enhancing the activity of MOFs for GOR. These findings offered an effective means for simultaneous productions of hydrogen fuel and high value-added chemicals using one hybrid electrolyzer with low energy input.

Influence of Be vacancy on 2D BeN4 single-layer for enhanced H2S sensing: prediction from first-principles simulations

Abstract A notable surge in research interest directed towards the exploration and development of two-dimensional materials, specifically in the realm of advancing nano-devices, with a special focus on applications in gas detection, has been observed. Among these materials, the spotlight has fallen on a newly synthesized single-layered Dirac Semimetal, known as BeN4, which holds great promise as a potential candidate for an efficient gas sensor. The current investigation uses first-principles calculations to examine the H2S detection capability of pristine and point-defect-tempted BeN4 single-layers. The H2S molecule has been observed to be weakly adsorbed on pure BeN4 through weak van der Waals interaction exhibiting very low adsorption energy of −0.0726 eV and insignificant charge transport. The impact of the Be vacancy point defect in BeN4 was the surge in H2S adsorption energy to −0.582 eV, manifested by enhanced charge transmission (0.02 e) from the H2S molecule to the BeN4 with Be defects. The reasonable physical steadiness and modest recovery time (6 ms) at ambient conditions indicate the possibility of Be point-defected BeN4 being a contender as a sensor material for designing and developing a robust H2S gas sensor. In addition, the sensor exhibited a selective response towards the H2S gas molecules. Our findings will provide a reference line for the fabrication of innovative H2S detectors, showcasing the practical implications of the observed enhancements in H2S adsorption energy and charge transmission in Be point-defected BeN4 structures.

Delving into the dissimilarities in electrochemical performance and underlying mechanisms for sodium and potassium ion storage in N-doped carbon-encapsulated metallic Cu2Se nanocubes

The large volumetric variations experienced by metal selenides within conversion reaction result in inferior rate capability and cycling stability, ultimately hindering the achievement of superior electrochemical performance. Herein, metallic Cu2Se encapsulated with N-doped carbon (Cu2Se@NC) was prepared using Cu2O nanocubes as templates through a combination of dopamine polymerization and high-temperature selenization. The unique nanocubic structure and uniform N-doped carbon coating could shorten the ion transport distance, accelerate electron/charge diffusion, and suppress volume variation, ultimately ensuring Cu2Se@NC with excellent electrochemical performance in sodium ion batteries (SIBs) and potassium ion batteries (PIBs). The composite exhibited excellent rate performance (187.7 mA h g−1 at 50 A g−1 in SIBs and 179.4 mA h g−1 at 5 A g−1 in PIBs) and cyclic stability (246.8 mA h g−1 at 10 A g−1 in SIBs over 2500 cycles). The reaction mechanism of intercalation combined with conversion in both SIBs and PIBs was disclosed by in situ X-ray diffraction (XRD) and ex situ transmission electron microscope (TEM). In particular, the final products in PIBs of K2Se and K2Se3 species were determined after discharging, which is different from that in SIBs with the final species of Na2Se. The density functional theory calculation showed that carbon induces strong coupling and charge interactions with Cu2Se, leading to the introduction of built-in electric field on heterojunction to improve electron mobility. Significantly, the theoretical calculations discovered that the underlying cause for the relatively superior rate capability in SIBs to that in PIBs is the agile Na+ diffusion with low energy barrier and moderate adsorption energy. These findings offer theoretical support for in-depth understanding of the performance differences of Cu-based materials in different ion storage systems.

High-Performance Ir1/CeO2 Single-Atom Catalyst for the Oxidation of Toluene.

The elimination of toluene is an obligatory target with increasing VOC emission in recent years. This study successfully prepared a single-atom Ir catalyst (Ir1/CeO2) by a simple incipient wetness impregnation method, confirmed by in situ CO DRIFTS and AC-HAADF-STEM. Compared to the cluster Ir catalyst (Ir/CeO2-C), Ir1/CeO2 exhibited excellent catalytic performance, stability, and water resistance for the oxidation of toluene. By Raman, H2-TPR, O2-TPD, and XPS experiments, abundant oxygen defects and a unique Ir3+-Ov-Ce3+ structure were formed for the Ir1/CeO2 sample because it had a lower oxygen vacancy formation energy. Furthermore, the DFT results revealed that the Ir1/CeO2 sample had a lower ring-opening energy barrier and adsorption energy of the ring-opening products, which was the rate-determining step for the oxidation of toluene. This work provides instructive insights into the construction of Ir/CeO2 catalysts for the highly efficient removal of VOCs.

Long-Life Zn Anode Enabled with Complexing Ability of a Benign Electrolyte Additive.

The development of aqueous zinc ion batteries (AZIBs) is hindered by several problems, including Zn dendrite/corrosion, side reactions, and hydrogen evolution reaction (HER). Herein, trisodium citrate (NaCit) additive is introduced into the ZnSO4 electrolyte to guide the preferred Zn(002) crystal plane growth, while the Cit- is preferentially adsorbed on the active sites to suppress the HER and Zn corrosion, thus achieving uniform Zn deposition without dendrites. The stable cycle life can reach 2000 h at 0.25 mA cm-2/0.05 mAh cm-2. The density functional theory simulations further indicate that the parallely placed Cit- has the lowest adsorption energy (-6.617 eV); it can form a weak interaction with Zn metal to promote the growth of (002) crystal planes. Furthermore, the assembled Zn//polyaniline full cell and pouch cell both exhibit good rate performance and long cycling stability. The complexation and dissolubilization effects of the NaCit additive provide a means for designing high-performance AZIBs.

Computational analysis of anionic dyes adsorption on the kaolinite (001) surface: Combination of quantum chemical calculations and molecular simulation methods

Clay minerals are increasingly used to remove dyes from wastewater. In recent times, computational simulation methods have become indispensable for investigating the adsorption mechanisms of dyes on clay surfaces at the molecular level. This study investigates the adsorption features of two acid dyes, namely acid blue 25 (AB25) and acid red 88 (AR88), on the (001) surface of kaolinite in an aqueous medium using density functional theory (DFT), Monte Carlo (MC), and molecular dynamics (MD) simulations. Quantum chemical parameters (QCPs) show that the AB25 molecule exhibits higher reactivity compared to the AR88 molecule. As well, analysis of the sigma profile reveals a moderate polarity of the two dye molecules studied in comparison with the water molecule. The low-energy adsorption configuration of AB25 and AR88 molecules show that each molecule is oriented parallel to the (001) surface of kaolinite over short distances. The adsorption energies indicate that the kaolinite (001) surface has high affinity towards AB25 in comparison with the AR88 molecule (Eads(AB25) = -926.01 Kcal.mol−1; Eads(AR88) = -742.08 Kcal.mol−1), which was supported by analysis of the self-diffusion coefficient (SDC) values (SDCAB25 = 7.79 × 10-10 m2.s−1; SDCAR88 = 1.4 × 10-9 m2.s−1). Additionally, calculation of the radial distribution function of the oxygen and nitrogen atoms of AB25 and AR88 molecules show the contribution of these atoms in the chemical interactions that take place with the (001) surface of kaolinite. The adsorption mechanism of the investigated dye molecules may be influenced by both donor–acceptor and van der Waals interactions. The theoretical results from this study could be useful for better understanding the adsorption mechanisms of other acid dyes on clay minerals.

Unravelling the synergy of platinum-oxygen vacancy in CoOx for modulating hydrogenation performance

Constructing high-efficiency catalysts with high activity and selectivity is the long-term pursuit in heterogeneous catalysis field. Metal–oxygen vacancy (Ov) synergy provides a promising route to realizing the goal. In this study, the Pt/CoOx catalysts with Pt–Ov dual sites are designed by atomic layer deposition (ALD) for selective hydrogenation of cinnamaldehyde, and the Ov property, Pt size and the spatial relationship of Pt and CoOx can be well modulated. Experimental and theoretical investigations indicate that the substrate and hydrogen can be activated on Ov and Pt nanoparticles, respectively. The Ov introduced by ALD not only preferentially activates CO bond of CALD to achieve high selectivity to CALA, but also enhances the ability to dissociate hydrogen on Pt nanoparticles through Pt-Ov electron transfer. Importantly, the optimized Pt40/CoOx-Ov catalysts with suitable Ov coordination and Pt sizes (2.5 nm) show lower adsorption energy for reactant molecules, obtaining significantly enhanced activity with a turnover frequency value of 202.5 molCALD·molPt-1·min−1 and obviously improved selectivity of desired products (93 %). This work offers a fundamental understanding of Pt–Ov synergy toward hydrogenation of unsaturated compounds.

Coordination environment engineering of MoS2-based nanocomposite by Ni atom incorporation for enhanced peroxymonosulfate activation

Ni-doped MoS2 can activate PMS effectively to degrade organic pollutants because the Ni doping can modulate the adsorption energy barrier of MoS2 to PMS molecule. However, how the coordination environment between Ni and MoS2 affects the activation of PMS to generate active species is poorly understood. In this paper, Ni substitutional or Ni adsorptive doping of MoS2 supported on TiO2/N-doped carbon nanofibers (designated as Nisub-MTC or Niads-MTC, respectively) were synthesized and used as PMS activators to degrade tetracycline (TC), respectively. In the case of Niads-MTC that the Ni atoms adsorb atop of S vacancies in MoS2, the reaction kinetic constant for TC degradation can reach 0.3381 min−1 within 10 min in Niads-MTC/PMS/Vis system. That is 1.84 times higher than that in Nisub-MTC/PMS/Vis system (0.1835 min−1), where the Mo sites in MoS2 are substituted with Ni atoms. This possibly due to that the Ni adsorptive doping can improve the regional activity of Mo-S bonds, which is more efficient than increasing the S vacancies by Ni substitutional doping. DFT calculations further support that the lower adsorption energy barriers of PMS were obtained on Ni adsorptive doping MoS2. Moreover, the main active species and possible TC degradation pathways were proposed. This work provides a new insight for designing metal doped heterogeneous catalysts with suitable coordination environments to improve PMS activation efficiency.

First Principles Investigation of C, Cl2 and CO Co-Adsorption on ZrSiO4 Surfaces for Carbochlorination Reaction.

The study of the adsorption behavior of C, CO and Cl2 on the surface of ZrSiO4 is of great significance for the formulation of the technological parameters in the carbochlorination reaction process. Based on first principles, the adsorption structure, adsorption energy, Barder charge, differential charge density, partial density of states and energy barrier were calculated to research the adsorption and reaction mechanism of C and Cl2 on ZrSiO4 surfaces. The results indicated that when C, CO and Cl2 co-adsorbed on the surface of ZrSiO4, they interacted with surface atoms and the charge transfer occurred. The Cl2 molecules dissociated and formed Zr-Cl bonds, while C atoms formed C1=O1 bonds with O atoms. Compared with CO, the co-adsorption energy and reaction energy barrier of C and Cl2 are lower, and the higher the C content, the lower the adsorption energy and energy barrier, which is beneficial for promoting charge transfer and the dissociation of Cl2. The 110-2C-2Cl2 has the lowest adsorption energy and the highest reaction activity, with adsorption energy and energy barriers of -13.45 eV and 0.02 eV. The electrons released by C are 2.30 e, while the electrons accepted by Cl2 are 2.37 e.