Differences In Adsorption Energies Research Articles

Understanding the Impact of Hydroxyls on Synthesizing the Bimetallic Alloy Pt3Co on Al2O3 for CO-PROX

The anchoring effect between surface hydroxyls (–OH) and metal species has been extensively utilized to enhance catalyst stability. Nevertheless, few studies have investigated the impact of alloying process involving different types of –OH species. In this research, we discovered that the formation of the alloy particles Pt3Co was significantly influenced by the presence of distinct –OH species on Al2O3. Intriguingly, those Pt3Co alloy particles exclusively formed on α-Al2O3 owing to the weak interaction between both Pt and Co species and the triply bridging hydroxyls (µ3-OH). In contrast, Pt and Co species were found to be separately dispersed on γ-Al2O3 because of the strong anchoring effect of terminal hydroxyls (µ1-OH), especially for Co atoms. Density functional theory (DFT) calculations highlighted the difference in adsorption energies of the two metals on different hydroxyl groups, providing a theoretical rationale for the influence of hydroxyl groups on alloy formation. The presence of Pt3Co alloy resulted in a fourfold increase in the specific catalytic rate of Pt3Co/α-Al2O3 in CO-PROX compared to Pt3Co/γ-Al2O3. Arguably for the first time, this study demonstrates the association between alloy formation and –OH groups, providing a unique perspective on the design of alloy catalysts.

Modulating the electronic structure of Ni and Co in core-shell structured catalysts to enhance the efficiency of reductive amination of pyruvic acid

A core-shell structured catalyst 3Ni-7Co@SiO2-0.2 was created to facilitate the reductive amination of pyruvic acid into alanine and the yield of alanine is up to 99 %. The SiO2 shell played a crucial role in spatial isolation effect, preventing the direct hydrogenation of pyruvic acid and improving the selectivity of alanine. By inter-doping Ni and Co, the electronic structure and properties are adjusted, the d-band center is reduced which is beneficial to the desorption of the product and the reaction barrier is reduced. Furthermore, it is proposed that catalysts exhibit better reductive amination reaction performance when there is a smaller difference in adsorption energy between NH3 and H2 atoms on the metal surface.

Metal-enhanced carbon-nitrogen material for selective detection of hazardous gases: Insights from interface electronic states

In this study, utilizing density functional theory, the C3N1 monolayer modified by Ir, Pd, Pt, and Rh atoms (Ir/Pd/Pt/Rh-C2N1) was chosen for selective adsorption of C2H2 amidst multiple gases (H2O, C2H2, and C4H10O2). According to the results of cohesive energy and ab initio molecular dynamics simulations, it is indicated that precious metal atoms can be stably anchored on the monolayer while enhancing the conductivity of the material The analysis of the electrostatic potential and work function determined the highly active sites and electron release capacity. In addition, the adsorption energy and distance disclosed the gas-solid interface structure of multiple gases on the Ir/Pd/Pt/Rh-C2N1 monolayer. Importantly, C2H2 exhibits strong responses to p-type semiconductor Pt-C2N1 and n-type semiconductor Ir-C2N1, respectively. Crystal Orbital Hamilton Population reveals the difference in adsorption energy due to modifications involving four precious metals. Interestingly, for the first time, the density of states calculation reveals that under the coexistence of multiple gases, the Pt/Ir-C2N1 monolayer effectively eliminates the interference of other gases and has a unique response only to C2H2. In real situations, with the basis of Gibbs free energy and Einstein's law of diffusion, it was determined that Pt-C2N1 and Ir-C2N1 showed excellent hydrophobicity, a wider temperature range, and a low diffusion activation energy barrier. In summary, Pt-C2N1 and Ir-C2N1 detect C2H2 without interference, maintaining fundamental principles, responsiveness, stability, and versatility unaffected by external factors.

Controllably hydrolytic dehydrogenation of NH3BH3 over micropore-dominant porous carbon confined RuPd ultrafine alloys

At present, controllable producing hydrogen from the catalytic hydrolysis of ammonia borane (AB, NH3BH3) is very meaningful and challenging. Therefore, developing an effective catalyst for the reaction, clarifying its catalytic mechanism, and realizing controllable hydrogen release are extremely indispensable. In this work, RuPd nanoalloys are evenly confined by the agricultural waste wheat straw-derived carbon (denoted as WSC) with a micropore-dominant porous structure and plentiful N/O doping. Attributing to the particular support effect of WSC and the interesting RuPd alloy effect, the as-prepared bimetallic catalysts provide encouraging catalytic performance in AB hydrolysis. Catalyzed by the optimal Ru0.50Pd0.50@WSC, the turnover frequency (TOF) and hydrogen evolution rate are 214.5 min−1 and 50800 mL min−1 g−1, respectively, and the apparent activation energy is only 23.2 kJ mol−1. Moreover, introducing proper NaOH (1.5 M) further accelerates hydrogen release (TOF = 502.8 min−1, specific rate = 119100 mL min−1 g−1). The isotope experiments depict a kinetic isotope effect of 2.85, evidencing the vital role of the hydrogen–oxygen bond scission in this catalytic reaction. More importantly, benefitting from the difference in adsorption energy and strong coordination ability, the “on–off” control for the hydrolysis of AB over Ru0.50Pd0.50@WSC can be realized with the Zn2+/EDTA2- system. This study provides an attractive metal alloy catalyst and some insights for the controllable hydrolysis of AB.

Solvent-Porphyrin Pseudo-Polymorphs: A DFT and Statistical Mechanical Study

Well defined monolayers of solvent incorporated cobalt(II) octaethylporphyrin (CoOEP) on Au(111) can be formed in toluene (TOL) and in 1,2,4 trichlorobenzene (TCB). These structures are pseudo rectangular and one-to-one in composition (REC). These structures only form when the initial exposure of Au is to very dilute solutions of CoOEP. When the initial Au exposure is to high CoOEP concentration solution, only the porphyrin adsorbs in the well-known pseudo hexagonal (HEX) structure. Attempts to convert the REC structure to HEX by the addition of concentrated CoOEP at 298K were never observed for the TCB case, and occurred slowly in the TOL case. Density functional theory (DFT) and statistical mechanics are used to investigate the rates of desorption and the equilibrium concentrations for the TOL-REC, TCB-REC, and HEX system. Two different DFT functional types (GGA and meta-GGA), both with corrections for van der Waals forces, were used. In order to address both the energies of the activated states and the kinetics of desorption in contact with liquid solvent, we will use a method proposed by Charlie Campbell for estimating the difference in adsorption energy of a molecule in the presence and absence of a liquid solvent, which assumes pairwise interfacial bond additivity. The results of these calculations indicate that the REC forms only exist because of the rapid adsorption and desorption of the solvents and the slow desorption and diffusion of the porphyrin. We note that computed desorption rates are extremely sensitive to the actual activation energy and, based on the difference in values produced by the two computational methods, are not quantitively reliable. The computed equilibrium state at 298K, on the other hand, is predicted to be the HEX form independent of computational method and solution concentration for all practical values of the concentration. Thus the REC structures are kinetically controlled while the HEX structure is the equilibrium structure.

Biphenyl monolayer construction with single transition metal doping as electrocatalysts for conversion CO2 to fuel

Developing sophisticated electrocatalysts is crucial in capturing chemically unreactive CO2 and transforming it into valuable products like fuel. This is essential for effectively tackling the issues of energy crisis and greenhouse gas emissions while maintaining considerable sustainability standards. Nevertheless, effectively managing the selectivity of products while maintaining a small overpotential remains a challenging task. Present work utilized density functional theory (DFT) for studying electrocatalytic potential of various single transition metals (TMs), such as cobalt, iron, and manganese, in process of carbon dioxide reduction reaction (CO2RR). Effectiveness of CO2RR was evaluated for each TM by analyzing their interaction with reaction intermediates (CHO, CO, and COOH) when incorporated into biphenyl monolayer (BPM) systems. Based on the analysis of ΔE values and barriers, it was determined that incorporating Fe into the biphenyl monolayer system is the most efficacious approach for the CO2RR to generate methane. This configuration achieves an exceptionally low overpotential potential (UL) of −0.36 V. In hydrogen evolution reaction (HER), it was observed that CO2 exhibits a higher affinity for occupying the activation site on Fe-BPM compared to H2. This difference in adsorption energy (Ead) (−0.94 eV for CO2 vs. −0.43 eV for H2) highlights their distinct behaviors. Additionally, Fe-BPM effectively suppresses the HER during the CO2RR process, as indicated by the HER's UL of −0.43 V. Findings of present study are anticipated to provide a novel direction in the advancement of electrocatalysts with low potential, while simultaneously exhibiting remarkable selectivity and activity for CO2RR.

Robust synergistic effect between Zn1Mo1 bifunctional TiO2 for efficient ethyl levulinate production from furfural alcohol

Bifunctional ZnxMoy-TiO2 were prepared through sol-gel methodology for efficient furfuryl alcohol (FAL) alcoholysis to ethyl levulinate (EL). From the comprehensive analysis, the abundant Brønsted and Lewis acidity distribution, enhanced reducibility ability, and the synergistic effect between Zn and Mo were found in Zn1Mo1–TiO2. Specially, Zn played an important role in enhancing acidity strength and reducibility from NH3-TPD and H2-TPR profiles, whereas Mo exhibited the highest FAL adsorption capacity. The simulative structure with the adjacent Zn–Mo and non-adjacent Zn–Mo with O vacancies in TiO2 showed no difference in FAL adsorption energy and bader charge transfer capacity. After optimization, Zn1Mo1–TiO2 exhibited the highest FAL conversion (98 %) and EL yield (80 %) with negligible 2-(ethoxymethyl)furan (EMF) and 5-ethoxy-5-(ethyl-oxidaneylidene) pentan-2-one (intermediate 4) yield under optimum condition (50 mg Zn1Mo1–TiO2, 170 °C, 7 h). Most importantly, the catalyst recyclability was performed in continuous flow until 700 min without obvious EL yield decrease. The rational design of the cost-effective bimetallic based TiO2 will drive the green and efficient EL production in industrial scale.

Ab initio study of the adsorption of O, O2, H2O and H2O2 on UO2 surfaces using DFT+U and non-collinear magnetism

In order to model correctly the corrosion of spent nuclear fuel under disposal conditions, it is important to understand its behavior in the presence of oxidants. To advance in this direction, we consider the oxidation of UO2. We investigate computationally the adsorption of various species on its three most stable surfaces: (111), (110), and (100), with emphasis on incorporating a full non-collinear PBE+U approach. Various species, namely O, O2, H2O and H2O2 are considered due to their relevance for the oxidation of UO2. The dissociation energy and an estimate for the dissociation barrier for O2 were obtained, using the preferred adsorption configurations of O and O2. The adsorption configurations for H2O in our study compare well with previous studies that used collinear approximations, both in terms of relative stability of configurations and bond lengths. Differences in adsorption energies were found, which may be important for reaction kinetics. Dissociative reactions in which the water molecule splits in hydrogen and hydroxyl occur only on one of the three surfaces. The hydrogen further reacts with a surface oxygen to also form a hydroxyl group. Not surprisingly, we find that H2O2 binds more strongly to the three surfaces than water (lower formation energy), and similar to H2O adsorption, dissociative reactions may occur. The dissociated hydrogen reacts with a surface oxygen to form a hydroxyl group and the hydroperoxyl molecule binds with a surface uranium. Our study, which includes a detailed study of electron transfer, magnetic structure and the preferred adsorption configurations, gives insight into the uranium oxidation states and the influence of surface geometry on adsorption. The findings contribute to a more comprehensive understanding of the early stages of UO2 oxidation.

Aluminum-induced electron structure on nickel phosphide for effective hydrazine‑assisted water splitting at large current density

Hydrazine-assisted water electrolysis emerges as a promising strategy to replace conventional device for effective hydrogen generation. Limited to the great difference of intermediate adsorption energy for hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR), the design and fabrication of bifunctional catalysts is still a knotty challenge in industrial conditions. Herein, Al-doped Ni2P nanoflower architecture grown in-situ on nickel foam (Al-Ni2P/NF) is fabricated through the combination of hydrothermal process and subsequent phosphorization treatment. Ascribed to the redistribution of electron state and optimization of reaction intermediate energy induced by Al, Al-Ni2P/NF expresses distinguished bifunctional catalytic performance with ultralow potentials of −205 and 300 mV at 500 mA cm−2 for HER and HzOR, respectively. When integrated into hydrazine-assisted water splitting as both the anode and cathode, only 0.717 V is required to reach a large current density of 500 mA cm−2. Specially, a novel integrated system driven entirely by sustainable solar energy is proposed, generating energy-saving hydrogen and purify hydrazine-containing sewage simultaneously. This work provides an attracting and practical path for accelerating the development of hydrogen economy.

Screening Efficient C-N Coupling Catalysts for Electrosynthesis of Acetamide and Output Ammonia through a Cascade Strategy of Electrochemical CO2 and N2 Reduction Using Cu-Based Nitrogen-Carbon Nanosheets.

Due to the limitation of the high-value-added products obtained from electrocatalytic CO2 reduction within an acid environment, introducing additional elements can expand the diversity of the products obtained during the CO2 reduction reaction (CO2RR) and nitrogen reduction reaction (NRR). Thus, coelectroreduction of CO2 and N2 is a new strategy for producing acetamide (CH3CONH2) via both C-C and C-N bond coupling using Cu-based nitrogen-carbon nanosheets. CO2 can reduce to CO, and a key ketene (*C═C═O) can be generated from *CO*CO dimerization; this ketene is postulated as an intermediate in the formation of acetamide. However, most studies focus on promoting the C-C bond formation. Here, we propose that C-N bond coupling can form acetamide through the interaction of *C═C═O with NH3. The acetamide is formed via a nucleophilic attack between *NH3 and the *C═C═O intermediate. The C-N coupling mechanism was successfully applied to expand the variety of nitrogen-containing products obtained from CO2 and N2 coreduction. Thus, we successfully screened Cu2-based graphite and Cu-based C3N4 as catalysts that can produce C2+ compounds by integrating CO dimerization with acetamide synthesis. In addition, we observed that Cu2-based C2N and Cu-based C3N4 catalysts are suitable for the NRR. Cu-based C3N4 showed high CO2RR and NRR activities with small negative limiting potential (UL) values of -0.83 and -0.58 V compared to those of other candidates, respectively. The formation of *COHCOH from *COHCO was considered the rate-determining step (RDS) during acetamide electrosynthesis. The limiting potential value of Cu2-based C2N was only -0.46 V for NH3 synthesis, and the formation of *NNH was via the RDS via an alternating path. The adsorption energy difference analysis both CO2 and N2 compare with the hydrogen evolution reaction (HER), suggesting that Cu2-based C2N exhibited the highest CO2RR and NRR selectivity among the 13 analyzed catalysts. The results of this study provide innovative insights into the design principle of Cu-based nitrogen-carbon electrocatalysts for generating highly efficient C-N coupling products.

Novel chiral composite membranes coated by microporous hyper-crosslinked polymer for efficiently enantioselective separation

With the rapid development of the pharmaceutical industry, efficient enantiomeric resolution is of great significance for the preparation of single enantiomer drugs. Herein, several kinds of chiral hyper-crosslinked polymer composite membranes (CHCPs/PSS) were fabricated by surface-initiated Friedel-crafts alkylation reaction on the porous SiO2 substrate for enantioseparation. The membrane fabrication conditions were optimized by changing various monomer concentrations, polymerization times and substrate pore sizes using phenylalanine as separated substance and the percent enantiomeric excess (ee%) reached 91.2 % with a permeability up to 6.31 × 10−2 m2/h which was 1012 folders higher than the traditional chiral polymer membranes. Besides, the enantioseparation of disparate enantiomers including clinical drug were also evaluated using CHCPs/PSS membranes to expand its application scope. The ee% and permeability reached 9.48 % and 5.13 × 10−1 m2/h for tryptophan and 24.4 % and 1.56 m2/h for ibuprofen, respectively. Static adsorption and quantum chemical computation were utilized to analyze the separation mechanism and the results indicated that the adsorption energy difference which resulted from the multiple interactions contributed to the effective separation of enantiomers. Consequently, this work will provide a new method for the application of chiral hyper-crosslinked polymer membranes in enantiomeric separation.

Enhancement of gas adsorption on transition metal ion-modified graphene using DFT calculations.

Graphene-based nanomaterial was widely used in gas sensors, detection, and separation. However, weak adsorption and low selectivity of the pristine graphene used for gas sensors are major problems. Here, using density functional theory (DFT) calculations, we reported the significant increase of four gas molecules (N2, CO2, C2H2, and C2H4) adsorption on the transition metal ion (Fe3+, Co2+, Ni2+)-modified graphene complex (Fe3+/Co2+/Ni2+-G) comparing to be absorbed on the pristine graphene (G). Moreover, the Co2+-G is suitable for the selective separation of C2H4/C2H2 due to the larger adsorption energy difference (8.5kcal/mol) between them. The addition of transition metal ions also decreased the HOMO-LUMO gap of the systems, which benefits the enhancement of electrical conductivity. This suggests that the transition metal ion-modified graphene can be used to distinguish the different gas molecule's adsorption, facilitating the design of graphene-based gas sensors and selective separation. All the density functional theory (DFT) calculations were performed by B3LYP with the GD3 dispersion method using Gaussian 16 software. The basis set 6-31G(d) was used for C, H, O, and N atoms, and Lanl2DZ was used for transition metal ions (Fe3+, Co2+, Ni2+). The DOS analysis and energy decomposition analysis were performed using the Multiwfn program.

Adsorption mechanism and compatibility of environmentally friendly insulating gas CF3I and its main decomposition products with Al and Cu(1 1 1) surfaces

Good environmental compatibility and excellent insulation performance make trifluoroiodomethane (CF3I) have the potential to replace SF6 in gas-insulated equipment. The gas–solid compatibility of CF3I, its main decomposed products (I2, C2F6, C3F8, C2F4, HF, CF3H, COF2), and environmental molecule H2O with the Al and Cu(111) surfaces is investigated based on first-principles calculations. The most stable adsorption configurations of Al and Cu(111) surfaces adsorbed by all gas molecules are constructed, and the interaction types between gas molecules and two metal surfaces are determined by adsorption energy (E ad), charge transfer, and charge density difference. The absolute E ad of CF3I and I2 adsorbed on Al(111) surfaces are 4.09 and 3.76 eV, respectively. In contrast, the absolute E ad of other gases adsorbed on Al(111) surfaces do not exceed 0.99 eV, indicating that CF3I and I2 have strong chemical interactions and poor gas–solid compatibility with Al(111) surfaces, while other gases exhibit good gas–solid compatibility with the Al surface. The absolute E ad of I2 (1.15 eV) adsorbed on Cu(111) surface is significantly larger than that of other gases-adsorbed systems (not exceeding 0.99 eV) including CF3I-adsorbed system, proving that the gas–solid compatibility of I2 with Cu(111) surfaces is worse than that of other gases. In addition, the reasons for the different compatibility of CF3I with Al and Cu(111) surfaces are analyzed in depth through the density of states.

MINI REVIEW ON RECENT ADVANCES OF THE ADSORPTION MECHANISM BETWEEN MICROPLASTICS AND EMERGING CONTAMINANTS FOR CONSERVATION OF WATER

Pharmaceuticals and microplastics have long been identified as water pollutants. Pollutants, including pharmaceutical compounds, have been shown to be transported by microplastics (MPs). In this mini-review, adsorption mechanism between microplastics and emerging contaminants were highlighted. Polyethylene is a non-polar, semi-cystalline microplastic with a density of 240 to 244 kg/m3. Besides, Ibuprofen adsorption onto microplastics is pH dependent. Non-polar or neutral compounds that are homogeneous and extremely hydrophobic in nature interact with non-polar and weakly polar plastics such as Polypropylene and Polyethylene. Furthermore, Molecular dynamic (MD) simulation can be employed to study the mechanism of interaction between MPs and contaminants. As a result, some studies show a complex interaction between polyethylene (PE) and certain contaminants, with no significant differences in adsorption energies, but sulfamethazine molecules effectively adsorbed on the MPs surface. In summary, this mini review shed lights on the insights of adsorption mechanism between these compounds.

π-Sticked Metal‒Organic Monolayers for Single-Metal-Site Dependent CO2 Photoreduction and Hydrogen Evolution Reaction.

Hierarchical self-assembly of 2D metal‒organic layers (MOLs) for the construction of advanced functional materials have witnessed considerable interest, due to the increasing atomic utilizations and well-defined atom‒property relationship. However, the construction of atomically precise MOLs with mono-/few-layered thickness through hierarchical self-assembly process remains a challenge, mostly because the elaborate long-range order is difficult to control via conventional noncovalent interaction. Herein, a quadruple π-sticked metal‒organic layer (πMOL) is reported with checkerboard-like lattice in ≈1.0 nanometre thickness, on which the catalytic selectivity can be manipulated for highly efficient CO2 reduction reaction (CO2RR) and hydrogen evolution reaction (HER) over a single metal site. In saturated CO2 aqueous acetonitrile, Fe-πMOL achieves a highly effective CO2RR with the yield of ≈3.98mmolg‒1h‒1 and 91.7% selectivity. In contrast, the isostructural Co-πMOL as well as mixed metallic FeCo-πMOL exhibits a high activity toward HER under similar conditions. DFT calculations reveal that single metal site exhibits the significant difference in CO2 adsorption energy and activation barrier, which triggers highly selective CO2RR for Fe site and HER for Co site, respectively. This work highlights the potential of supramolecular π…π interaction for constructing monolayer MOL materials to uniformly distribute the single metal sites for artificial photosynthesis.

DFT Calculations of Silver Atom Modified Tungsten Disulfide Monolayer as Promising Sensing Materials for Small Molecular Toxic Gases

In the contemporary context, the significance of detecting harmful gases cannot be overstated, as it profoundly affects both environmental integrity and human welfare. In this study, theoretically, density functional theory was employed to explore the adsorption behavior of three prevalent hazardous gases, namely CO, NO2, and SO2, on silver-atom-modified tungsten disulfide (WS2) monolayer. The multifaceted analysis encompasses an array of critical aspects, including the adsorption structure, adsorption energy, electron transfer, and charge density difference to unravel the adsorption behavior. Further exploration of electronic properties encompassing band structure, density of states (DOS), and work function was conducted. The ambit of our exploration extends to the desorption properties based on adsorption-free energies. Among these gas molecules, NO2 stands out with the highest adsorption energy and the most substantial electron transfer. Notably, each of these adsorption processes triggers a redistribution of electron density, with NO2 exhibiting the most pronounced effect. Furthermore, the adsorptions of CO, NO2, and SO2 induce a noteworthy reduction in the band gap, prompting the reconfiguration of molecular orbitals. Additionally, the adsorption of these gases also leads to an increase in the work function of Ag-WS2 to a different extent. Our investigation of desorption properties uncovers that Ag-WS2 can adeptly function at ambient temperatures to detect CO and SO2. However, for NO2 detection, higher temperatures become imperative due to the necessity for poison removal. The implications of our findings underscore the tremendous potential of Ag-WS2 as a sensing material for detecting these hazardous gases. Our research extends to the broader realm of surface modification of transition metal dichalcogenides and their promising applications in the domain of gas sensing.

Selective deep desulfurization of liquefied petroleum gas on Ni/ZnO-based catalyst

Process of selective deep desulfurization of liquefied petroleum gas (LPG) was developed using a Ni/ZnO-based catalyst. Ethyl mercaptan, dimethyl disulfide and methyl disulfide were used as model compounds in LPG to investigate sulfides conversion over different catalysts. All three model sulfides were totally removed over the composite catalyst at above 300 °C in hydrogen atmosphere. Desulfurization of LPG from FCC unit were studied in a micro-fixed bed reactor, and scaled up in a fixed-fluidized bed reactor. Results showed that highly selective desulfurization of LPG could be achieved using the composite catalyst when the sulfur loading of catalyst was in a particular range. The sulfur content of LPG could be decreased to lower than 2.0 μg·g−1 with an olefin loss ratio of less than 1.5 %. X-ray photoelectron spectroscopy (XPS) characterization indicated that the interaction of Ni with S strengthened with the increasing of sulfur loading. Density functional theory calculations showed that the pre-coated S on Ni (111) surface increased the adsorption energy difference between propylene and sulfides which was helpful for the retention of propylene during desulfurization on Ni/ZnO-based catalyst.

Amorphization Engineering of Bimetallic Metal‐Organic Frameworks to Identify Volcano‐Type Trend toward Oxygen Evolution Reaction

AbstractAmorphous metal‐organic frameworks (MOFs) with aperiodic atomic arrangements, featuring high intrinsic activity and rich active sites, have emerged as promising oxygen evolution reaction (OER) catalysts. However, the quantitative structure‐activity relationships (SARs) that determine the OER activity, the key to a rational catalyst design, remain unresolved. Inspired by controllable amorphization engineering, the amorphous MOF structures are rationally constructed as an ideal platform to explore the SAR in catalyzing OER. The mechanistic studies show that the OER activity could be volcano‐shape correlated with either constant adsorption energy difference between OOH* and O* (ΔGOOH* − ΔGO*) or the position of the d band center. The amorphous MOF (Ni8Co2‐BDC), situated close to the volcano summit, possesses an appropriate Ed energy level, which exhibits the balanced intermediates adsorption/desorption ability and consequently results in the boosted catalytic activity and long‐term stability. This work supplies new perspectives to investigate the SAR in amorphous MOF structures, thereby guiding the rational design of advanced OER catalysts.

I-V characteristics and adsorption properties of ZnO/rGO/ZnO for gas sensing detection

The heterostructure consisting of zinc oxide and reduced graphene oxide (ZnO/rGO/ZnO) is prepared on cotton fabric by repeated immersion and magnetron sputtering. In addition, the gas selectivity of the sample is analyzed based on I-V characteristics under different gas atmospheres (air, methanal, ethanol, acetone and toluene). Compare with that in air atmosphere, the I-V characteristic curve under toluene gas atmosphere changes significantly, and the current decreased significantly. The experimental results show that the samples exhibit high selectivity. In order to study the intrinsic physical characteristics of the heterostructure after gas adsorption, the band structures, density of states (DOS), adsorption energy (Ead) and charge density difference (CDD) are calculated based on density function theory (DFT). The existence of rGO results in a high electrical conductivity, which is consistent with the experimental results. Meanwhile, toluene has the highest Ead (-0.85 eV) and charge transfer (0.67 e). The charge transfer results prove that a large number of electrons are transferred from the surface of the heterostructure to the vicinity of toluene molecules, which leads to a change in the electrical conductivity of the heterostructure. Based on the excellent gas selectivity, the application of cotton-based ZnO/rGO/ZnO structure in gas sensing field is promoted.

DFT investigation and Polypyrrole sensitization mechanism of a selective NO2 sensor for room temperature application based on MXene@PPy heterojunction

Assembling a heterojunction-based composite nanomaterial to simultaneously achieve higher response and superior selectivity towards NO2 under room-temperature conditions remains a great challenge. In this work, the MXene@Polypyrrole heterojunction was synthesized via a facile in-suit chemical polymerization approach. The distribution of sphere-like PPy nanoparticles was confirmed via various characterization techniques. The response value of the 0.5MXP sensor toward 50 ppm NO2 is significantly higher than that of the pristine MXene based sensor, entailing greater response (6.5-fold). Nearly 98.11% recovery to the base resistance was observed in each sensing cycle. Noteworthy, the Schottky barriers formed between MXene and PPy contact surface, leading to the ideal selectivity and a lower limit of detection. Additionally, the sensor was tested for a 31-days-period with minimal deviation, predicting outstanding reproducibility and durability. The detailed polypyrrole sensitization mechanism containing selectivity mechanism, underlying heterojunction mechanism as well as the Density Function Theory (DFT) calculation were also revealed, offering new ideas for the development of room-temperature nitrogen dioxide sensors. Simultaneously, DFT calculation (21 models, 42 images) revealed the adsorption energy, electron transfer, and charge density differences between the NO2 molecules and the substrate (MXene, PPy and MXene@PPy). In summary, the outstanding MXene surface functionalization has been exploited by decorating with polypyrrole (PPy) nanoparticles.