Lower Adsorption Energy Research Articles

Encapsulating Fe-Co bimetal inside carbon aerogel to boost electron transfer for efficient heterogeneous electro-peroxone oxidation of organic pollutants

We fabricated a novel Fe-Co bimetal encapsulated inside carbon aerogel sphere (Fe2Co@CS) to improve the electro-peroxone (EP) process. The degradation and mineralization of p-nitrophenol (p-NP) were 100% (15 min) with rate constant of 0.314 min−1 and 83.8% (60 min) in Fe2Co@CS/EP, respectively. Fe2Co@CS was composed of defective graphite carbon and Fe2Co alloy. The presence of metal–oxygen-carbon (M-O-C, MFe/Co) bonds promoted interface electron transfer from carbon layer towards Fe2Co alloy, which was advantageous to the reduction of ≡Fe3+/≡Co3+. Moreover, the Fe-Co synergistic effect also accelerated the interfacial catalytic reaction for activating O3 and H2O2. The quenching experiment and EPR test indicated that ·OH, ·O2- and 1O2 were main reactive oxygen species (ROSs). DFT calculations showed that O3 had lower adsorption energy on Fe2Co@CS than H2O2, manifesting that catalytic ozonation played the key role in ROSs generation. In addition, ozone utilization efficiency in Fe2Co@CS/EP (ΔTOC/ΔO3 = 1.23–0.68) revealed 66-36% increase relative to those of EP (0.74–0.5). Fe2Co@CS was an efficient catalyst over a wide pH range (3–11) with permissible iron and cobalt releases. The Fe2Co@CS/EP process exhibited high-performance for degrading different pollutants under high salinity condition with coexistence of Cl−, NO3− and SO42−. For treating real coal wastewater, the TOC removal was 52.7% at 4 h with low EEC (0.038 kWh (g TOC)−1). This study provided an efficient method for the development of EP in wastewater treatment.

Insights into Selective Mechanism of NiO-TiO2 Heterojunction to H2 and CO.

The construction of p-n heterojunctions has become a widely adopted strategy for achieving the selective detection of reducing gases, including H2 and CO. Nevertheless, the elucidation of the gas selectivity mechanism at the nanoscale remains elusive. First-principle calculations provide an attractive avenue for comprehending the influence of coordination structures on gas-sensitive selectivity, thereby unveiling the structure-activity relationship of p-n heterojunction sites. In this study, we investigate the selective adsorption behavior of H2 and CO on a NiO-TiO2 heterojunction using density functional theory. The results of d-band center analysis confirm that the NiO-TiO2 heterojunction with adsorbed oxygen significantly enhances the adsorption stability of reducing gases. Intriguingly, our calculations reveal that H2 has a higher affinity for adsorbed oxygen on the heterojunction surface compared to that of CO, corresponding to a lower H2 adsorption energy. Density of states (DOS) results indicate that the NiO-TiO2 heterojunction, with preadsorbed oxygen, exhibits ultrahigh selectivity with an n-type gas-sensitive response to H2, effectively eliminating the cross-sensitivity observed with CO, as confirmed by gas-sensitive characterization research. The sensing mechanism of the NiO-TiO2 heterojunction's selective detection of H2 without interference from CO can be visually explained by electron transfer and potential barrier changes, paving the way for future developments in novel, selective gas-sensitive materials.

Adsorption of hydrated Fe(OH)<sup>2+</sup> on the kaolinite surface: A density functional theory study

The present study employed density functional theory (DFT) to analyze the adsorption configuration and mechanism of Fe(OH)<sup>2+</sup> on the kaolinite (001) surface. The findings demonstrated that Fe(OH)<sub>2</sub>(H<sub>2</sub>O)<sup>4+</sup> is the main type in which hydrated Fe(OH)<sup>2+</sup> can be found in aqueous solution. On the surface of kaolinite, Fe(OH)<sub>2</sub>(H<sub>2</sub>O)<sup>4+</sup> will be adsorbed. There are two forms of adsorption: outer-sphere and inner-sphere coordination (monodentate/bidentate) adsorption. Fe(OH)<sub>2</sub>(H<sub>2</sub>O)<sup>4+</sup> has a moderate propensity to adsorb on the alumina octahedral sheet of kaolinite when the outer-sphere coordination adsorption takes place. In cases of inner-sphere coordination adsorption, Fe exhibits a tendency to form monodentate adsorption compounds in conjunction with Ou atoms. Additionally, it prefers to create bidentate adsorption compounds through coordination with both Ot and Ou atoms. The adsorption mechanism analysis results show that the ionic property of Fe atom decreases after outer-sphere coordination adsorption. After inner-sphere coordination adsorption, some electrons of Fe atom are transferred to the surface O atom. The presence of electrons between the Fe and O atoms enhances the formation of bonds, hence enhancing the covalent nature of the Fe-O bond. Theoretical FT-IR (Fourier transform infrared spectroscopy) calculations show that the formation of Fe-O chemical bonds. Because of the lower adsorption energy and more chemical bonds, hydrate Fe(OH)<sup>2+</sup> is more likely to be bidentate adsorbed on the kaolinite surface.

Metal organic framework template method for the preparation of bimetallic oxide CunCoOx catalysts for the catalytic oxidation of volatile organic compounds

A series of CunCoOx bimetallic oxides were synthesized by calcination of xCu/ZIF-67 precursors pre-impregnated with Cu2+. The Cu7CoOx catalyst demonstrated remarkable reactivity, reaching about 90 % conversion of toluene and ethylene at 194 °C and 162 °C. Additionally, Cu7CoOx was deemed suitable for applications at high space velocities, and also displaying superior stability. The physicochemical properties of CunCoOx were investigated by SEM, TEM, XRD, FTIR, BET, Raman, TG, O2-TPD, H2-TPR and XPS characterizations. The excellent catalytic performance of Cu7CoOx is attributed to the strong interaction of the two metal oxides, excellent redox ability, abundant lattice defects, more reactive oxygen species and higher concentrations of Co2+ and OLatt species. Density functional theory (DFT) calculation revealed CuO/Co3O4 (220) (Eads,O2 = −0.92 eV, Eads,toluene = −1.52 eV) displayed lower adsorption energy for toluene and oxygen molecules than Co3O4 (220) (Eads,O2 = −0.30 eV, Eads,toluene = −0.90 eV), which was favorable for the catalyst to catalyze the oxidation of VOCs. The possible degradation mechanism of toluene on Cu7CoOx was revealed using in situ DRIFTS. Thus, this work provides a non-noble metal catalyst with great application potential in VOCs treatment.

Physicochemical and adsorptive properties of biochar derived from municipal sludge: sulfamethoxazole adsorption and underlying mechanism

Municipal sludge waste could be transformed into useful biochar through pyrolysis process. In this study, municipal sludge-derived biochar (SBC) was successfully synthesized via the one-pot pyrolysis method, and the yield of sludge biochar gradually decreased with the pyrolysis temperature increased from 300°C to 800°C. The sludge biochar exhibited an alkaline surface due to the gradual accumulation of ash and the formation of carbonate and organic anion during high-temperature pyrolysis process. Moreover, the prepared samples were analyzed by different characterization techniques including BET, SEM, and XPS. Adsorption experiments using the optimized biochar sample of SBC800 resulted in a 95% sulfamethoxazole (SMX) removal efficiency and the maximum adsorption capacity of 7033.4 mg/kg, which was 47.5 times higher than that of SBC300. The adsorption process of SBC800 for SMX was more in line with the Freundlich and D-A isotherm model, the whole process was an exothermic reaction. SBC800 could effectively remove SMX through pore filling effect, electrostatic attraction, hydrogen bonding, hydrophobic effect, and π-π EDA interaction. Site energy distribution analysis showed that SMX preferentially occupied the high-energy adsorption site of SBC800, and then gradually diffused to the low-energy adsorption site. This study proposed a sustainable method for recycling municipal sludge for organic pollutant removal.

Copper atom-doped g-C3N4 nanocomposites for enhanced photocatalytic degradation of tetracycline

Inorganic photocatalysts with excellent photocatalytic reactivity have significant potential for wastewater treatment. In this study, using sodium copper chlorophyllin (SCC) as a copper source, Cu atoms were incorporated into the center cavities of g-C3N4 nanosheets by hydrothermal-calcination combined processes. Cu atoms doping led to a narrower optic band gap and the dramatic improvement in photocurrent response as well as corresponding declines in the intensity of electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) spectra. Consequently, the photocatalytic property the Cu/g-C3N4 was enhanced dramatically as evidenced by a 53.4% increase in the photocatalytic degradation rate of tetracycline. Superoxide ions and hydroxyl radicals were found to be the main reactive oxygen species (ROS) causing the degradation. The increased photocatalytic capability of Cu/g-C3N4 might be attributed to the increased chance of intersystem crossing in photosensitizing process of Cu/g-C3N4 as well as the lowered adsorption energy required for the adsorption of O2 to the catalyst. Minor decline in the photocatalytic efficiency of Cu/g-C3N4 was observed while the crystal structure of the Cu/g-C3N4 remained stable after three cycles of tetracycline degradation. These results indicated the good stability of Cu/g-C3N4 and the possibility of recycling the catalyst during the photocatalytic applications.

Molecular modelling of Al24N24 nanocage for the chemical sensing of phosgene and mustard chemical warfare agents: First theoretical framework

This research uses the efficiency of nanostructured Al24N24 for the rapid detection and sensing of phosgene and mustard chemical warfare agents (CWA). Frontier molecular orbitals (FMO), natural bond orbitals (NBO), density of states (DOS), topological analysis like non-covalent interactions (NCI) and quantum theory of atoms in molecules (QTAIM), sensing mechanism, and recovery time analysis were used to assess the adsorbing capabilities of the investigated Al24N24-nanocage. Mustard gas adsorption energy was strongest, ranging between −25.064 to –22.928 Kcal. Phosgene complexes had lower adsorption energies than mustard complexes ranging from −12.818 to −5.422 Kcal. The Frontier molecular orbitals (FMO) study demonstrates that phosgene and mustard gas adsorption on Al24N24 nanocage reduces the energy gap. Adsorption of phosgene results in the lowest energy gap of 2.91 eV (-29 %) for three complexes, namely P-Cl@4m, PO@6m, and P-planer@4m; hence, a much better sensing response 2.77 × 10−1 and a quicker recovery time of 3.93 × 10−10sec. These complexes have high softness (0.344 eV), low hardness (1.455 eV) and chemical potential of (-4.721 eV), which indicate high reactivity and low stability. Consequently, the Al24N24 nanocage is recommended as a fine future sensor for sensing phosgene and mustard CWA, with a much better response for phosgene.

Highly effective degradation of ibuprofen by alkaline metal-doped copper oxides via peroxymonosulfate activation: Mechanisms, degradation pathway and toxicity assessments

Redox ratios of Cu2+/Cu+ and adsorbed oxygen species (Oads) have shown great activity toward radical generation by activating peroxymonosulfate (PMS). Herein, different alkaline metal oxides (CaO, MgO and BaO) and various amounts of CaO are incorporated into CuO, which could tune the main active sites of redox ratios of Cu2+/Cu+ and Oads. The results show that CaO-CuO-5% exhibits the outstanding performance of PMS activation toward ibuprofen (IBF) degradation with excellent kinetics (k = 0.812 min−1). The X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculation show that the CaO-CuO-5% has the higher electron density with superior electron transfer ability and lower PMS adsorption energy. Based on radical scavengers and electron paramagnetic resonance spectrometer (EPR), a nonradical process is proposed to play the dominant role. The degradation pathway and the corresponding toxicity of degraded intermediates with residue PMS after reaction is evaluated by LC-MS/MS and bioassay experiments, indicating the lower antagonistic influence on human hormone receptors after advanced oxidation process. Mitigation of the Cu leaching with cyclic stability can be achieved. This study provides a facile method to optimize high-performance catalysts to activate PMS and offer practical environmental applications in the remediation of emerging contaminants.

The effect of Ir and Sc on the emission capacity of W–Ir matrix scandate cathodes prepared via a novel in situ method

The size and distribution of Sc2O3 in the composite powder precursor has great effect on the emission property of scandate cathode. By one-step in-situ synthesis method, the composite powder exhibits the structure of quasi-spherical Sc2O3 nanoparticles grown in situ on the surface of W/Ir grains, and the obtained W–Ir cathode with 3wt % Sc2O3 could provide the emission current density of 83.43 A/cm2 at 900 °Cb, which is higher than other W–Ir mixed matrix scandate cathodes and W matrix scandate cathode. The XRD results showed that the high emission ability depended on the high content of active phase α-Ba2ScAlO5 and low content of non-active phase BaAl2O4. In-situ TEM has been applied to observe the microstructure evolution of the cathode surface at high temperature for the first time. A serial change in the microstructural features of cathode surface and the migration of Ba, Sc and O on the substrate surface has been found, confirming the formation of Ba-Sc-O active layer. The first-principles calculations indicate that the active substances (Sc) are more stable (low adsorption energy of − 8.58 eV) on the IrW matrix cathode surface than on the tungsten matrix cathode surface, which is consistent with the low evaporation rate of the active substance detected by TFMS technique. Besides, the interaction between the active substance and the matrix was strengthened due to more electron transfer of Sc (1.88 e) and Ba (1.45 e), therefore lowering the work function. The feasible preparation technique makes such a cathode promising for applications in high-power microwave devices.

DFT study on adsorption of small gas molecules on Pt-capped armchair and zigzag single-walled carbon nanotubes

The adsorption of small gas molecules (CO, O2 and N2) on Pt-capped armchair and zigzag single-walled carbon nanotubes (SWCNT) has been investigated by density functional theory (DFT) method to determine the potential for gas sensor detection. Results indicated that O2 and N2 molecules with lower adsorption energies (1.66 eV and 1.00 eV) exhibited weak chemical adsorption on SWCNT(4,4)-Pt. However, CO demonstrates strong chemical adsorption with a high adsorption energy of 2.23 eV on SWCNT(4,4)-Pt. The adsorption energy of CO on SWCNT(7,0)-Pt shows the chemical adsorption between CO and SWCNT(7,0)-Pt. In addition, these findings also implied Pt-capped SWCNT could act as small gas molecule sensors to detect CO toxic gas at room temperature. In this system, CO is the electron donor and SWCNT-Pt is the electron receptor. The interaction of Pt and carbon nanotube backbone delocalized π electrons could not only increases the conductivity of SWCNT-Pt, but also enhances the conductivity of SWCNT-Pt-CO. The HOMO-LUMO gap (Δε) of Pt-capped SWCNT(7,0) reduced from 0.43 eV to 0.39 eV after CO adsorption, and the Δε value of Pt-capped SWCNT(4,4) decreased by 0.08 eV. The electrical conductivity of Pt-capped armchair and zigzag SWCNT has increased after the adsorption of CO molecule. The results may be helpful for designing a promising Pt-capped SWCNT-based CO sensors.

Morphological Effect on the Surface Activity and Hydrogen Evolution Catalytic Performance of Cu2O and Cu2O/rGO Composites

Different cuprous oxide (Cu2O) particle forms, including the octahedron, truncated octahedron, cube, and star-like forms, are synthesized through chemical reduction under different reaction conditions. The correlation between the morphology and the catalytic activity of hydrogen evolution reactions (HERs) is investigated. It is discovered that the Cu2O particles with a higher 111/100 facets (r) ratio have a higher oxidation resistance and higher activity in HER catalysis, as supported by the density functional theory (DFT) calculation results. This improvement is attributed to the fact that more Cu+ terminated atoms on facet 111 provide more active sites, as measured using their electroactive area, as well as the lower H2 adsorption energy on that facet. To enhance Cu2O’s HER performance, cuprous oxide particles are deposited on reduced graphene oxide (rGO) through a hydrothermal method. XPS and XRD show a CuO layer on the composite surface, which reduces the Cu2O corrosion in the reaction. Overall, Cu2O/rGO composites exhibit a better particle distribution, increased active sites, and improved charge separation. The best electrocatalyst in this study is the Cu2O/rGO with a star-shaped form, with an overpotential of −458 mV. Its improved performance is attributed to the presence of unsaturated active sites with a higher reactivity, such as the edges and corners. SEM studies of this composite after catalysis indicate that Cu2O undergoes structural reconstruction during the reaction and reaches a more stable structure.

Confined tuning of the charge distribution of Pt electrocatalyst for reinforcing anti-poisoning ability: Toward efficient separation of hydrogen from gases containing ammonia

The development of catalysts for hydrogen oxidation reaction (HOR) with enhanced resistance to ammonia poisoning is an important factor in the practical application of hydrogen electrochemical purification devices (HEPDs). This paper reports on the creation of a highly active and anti-ammonia HOR catalyst developed by tuning the charge distribution of the support material through nitrogen-doping of carbon. The nitrogen-doped carbon-supported platinum catalyst (Pt-N2/KB, 2.03 wt% Pt) achieves a high mass activity and exchange current density of 2788 mA mgpt-1 and 1020 mA mgpt-1, respectively, which are 5.4 and 4.7 times higher than that of the comm. 20% Pt/C. The Pt-N2/KB catalyst also displays a lower percentage of current decay and enhanced electrochemical stability, indicating superior anti-ammonia toxicity in the tests with HEPD. Density functional theory (DFT) calculations reveal that the hydrogen adsorption free energy (ΔGH*) on the surface of Pt-N2/KB is close to zero and has a lower ammonia adsorption energy, thus accounting for its superior HOR activity and anti- ammonia poisoning ability. Consequently, this work facilitates the implementation of HOR catalysts for anti-ammonia poisoning in the HEPDs, thus accelerating the advancement of ammonia cracking for hydrogen production.

Synergistic effect of surface modification and effective interfacial charge transfer over faceted g-C3N4/ZnSe heterojunction to enhance CO2 photoreduction activity

Heterojunction and surface modification are promising methods to boost the photocatalytic CO2 conversion efficiency which help to optimize the redox ability of photocatalysts and enhance the separation efficiency of photogenerated charge carriers. Herein, a novel surface-modified and interfacial heterojunction of g-C3N4 (CN) over a faceted ZnSe (ZS) {CN/ZS} composite was developed to accelerate the transfer of photogenerated electrons (e−) and holes (h+) between the CN and ZS photocatalysts. This technology allows faster transfer of a larger quantity of excited reductive electrons to the surface of ZS with a lower CO2 adsorption energy. Based on photocatalytic CO2 reduction to CO and CH4, 3 mmol CN/ZS composite outperformed all as-prepared photocatalysts including pure CN and ZS, with yielding rates of 439 and 203 umolg−1, respectively, with 88 % CO2 selectivity. The improved photocatalytic activity and selectivity were attributed to enhanced visible-light absorption, improved CO2 activation and adsorption on the surface of the photocatalyst and facilitated charge transfer at the interface. This study offers a novel approach for precisely controlling the direction of photogenerated charge separation by constructing a heterostructure for CO2 photoreduction.

Mixed-biomass engineering achieves multi-doped highly-disordered hierarchical flower-like hard carbon for advanced potassium-ion battery

Potassium-ion batteries (PIBs) have emerged as a significant technology for large-scale energy storage. With merits of high abundance, sustainability, and low cost, hard carbons are employed as promising anodes for PIBs, yet distorted carbon lattice induces sluggish conductivity and structural degradation, posing key challenges of low power performance and inferior life span. Here, we proposed a mixed-biomass strategy to design a multi-doped flower-like carbon micro-sphere with major doping of N and trace doping of P and S (NPS-FCM) for advanced PIBs operation. The mixed-biomass engineering achieved inherently rich heteroatoms’ doping and highly disordered hierarchical configuration simultaneously. The NPS-FCM material with expanded lattice spacing, larger specific area, and abundant edge defects and pores, offers robust rate property, and impressive cycle life (1000 cycles with 0.147 ‰ capacity decay per cycle). The potassium-ion full cell (NPS-FCM//PTCDA) was also implemented to show a high median-voltage of 1.78 V and steady cycling. Density functional theory calculation convinced the upgraded electronic conductivity and lowered adsorption energy for potassium storage. This work highlights the importance of mixed-biomass’ cooperation to provide pivotal guidance for sustainable and advanced electrodes for next-generation energy storage.

Fe-Ni bimetallic adsorbent for efficient As2O3 removal from coal-fired flue gas under a wide temperature range: Experimental and DFT study

Adding metal oxides in the furnace can effectively control the emission of heavy metal arsenic in the coal-fired flue gas, and α-Fe2O3 has excellent adsorption performance. However, single metal oxides still have defects such as easy sintering or weak oxidation ability during use, which significantly impact the adsorption effect of arsenic. In this work, a new Fe-Ni bimetallic adsorbent was prepared by hydrothermal calcination, and its mechanism of As2O3 adsorption was investigated in depth through the combination of experiment and theory. The experimental results show that the FN8 (Ni-doped molar percentage is 8%) adsorbent exhibits excellent performance, and its arsenic adsorption capacity reaches 405.60 mg/kg, which is more than twice the adsorption capacity of α-Fe2O3. Ni doping can not only regulate the electron transfer between the α-Fe2O3 interface and As, but also promote the conversion of lattice oxygen to chemisorbed oxygen in the system. In the temperature range of 500 °C–900 °C, the prepared FN8 adsorbent can maintain a good microsphere structure, avoid sintering and provide more adsorption sites, and its arsenic capture capacity is stronger than α-Fe2O3. The density functional theory further reveals the microscopic mechanism of improving the oxidation performance of Fe-Ni adsorbent. The results show that Fe-Ni adsorbent has lower adsorption energy than α-Fe2O3. This is due to the synergism of Ni and O, which leads to the redistribution of electrons on the α-Fe2O3 (001) surface, and the Ni atom provides more free electrons for O atoms, which ultimately promotes the oxidation ability of Fe-Ni adsorbent and forms an As-O covalent bond. The Fe-Ni bimetallic composite adsorbent proposed in this work provides a new idea of bimetallic adsorbent for the effective adsorption of arsenic in the flue gas.

Physisorption-Mediated Charge Transfer in TiS2 Nanodiscs: A Room Temperature Sensor for Highly Sensitive and Reversible Carbon Dioxide Detection.

Real-time and high-performance monitoring of trace carbon dioxide (CO2) has become a necessity due to its substantial impact on the global climate, human health, indoor occupancy, and crop productivity. Two-dimensional materials such as transition metal dichalcogenides (TMDs) have gained significant interest in gas sensing applications owing to their intrinsically high surface-to-volume ratio. However, the research has been limited to prominent TMDs such as WS2 and MoS2. Specifically, the chemiresistive sensing performance of titanium disulfide (TiS2) has rarely been investigated. We present an electric-field-assisted TiS2 nanodisc assembly for the fabrication of a low-cost, low-power CO2 gas sensor based on charge transfer between physisorbed CO2 analyte molecules and TiS2 nanodiscs operating at room temperature. The physiochemical properties of the synthesized TiS2 nanodiscs were investigated via scanning electron microscopy (SEM), electron diffraction spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. The fabricated sensor demonstrated an ultra-high sensor response of 60%, a fast response time of 37 s toward 500 ppm CO2 gas, and the lowest detection limit of 5 ppm under ambient conditions. The low adsorption energies and vdW interaction between CO2 molecules and TiS2 resulted in easy desorption, allowing the sensor to self-recover without the need for external stimuli, which is hardly been witnessed in other 2D material analogues. Furthermore, the sensor has excellent reproducibility and stability for successive analyte exposures, as well as excellent selectivity for CO2 over other interfering gases. This reported sensor based on 2D TMDs is the first of its type to integrate such a broad range of sensor characteristics (such as high sensor response and sensitivity, rapid response and recovery times, a high signal-to-noise ratio, and excellent selectivity at room temperature) into a single, revolutionary device for CO2 detection.

Theoretical Analysis of Metals Supported on Tungsten Oxide Nanowires (W18O49) for Water Dissociation Reaction

AbstractPt is the cause of the high total cost of fuel cells and electrolyzers, leading to difficult commercialization. Here, various types of metal atoms, i.e., Pt, Pd, Ni, Ir, Ag, and Rh, suitable for catalysts are used and supported by W18O49 nanowires for oxygen evolution reaction (OER) by the density functional theory (DFT) method. Four adsorbate molecules involved in OER were tested on adsorption energy: OH, O, OOH, and OO. Although the adsorption energy of these adsorbate molecules indicates that W18O49 has low adsorption energy, the Gibbs free energy diagram demonstrates that W18O49 has high OER reaction energy. Pt, Pd, Ni, and Rh have the lowest Gibbs energy to initiate the reaction and reasonable Gibbs free energy for other OER reactions. Bimetallic or trimetallic active sites can be developed along with selecting other metals with Pt, Pd, Rh, and Ni to reduce the Gibbs free energy difference for the decomposition of OH to O and OOH to H2O. Ag metal can also be applied as a second or third metal because Ag exhibits a relatively low Gibbs free energy difference in the O to OOH step. A selectivity study of each step on bimetallic and trimetallic active sites needs to be performed.

Adsorption behavior of Janus MoSiGeN4 monolayer for gas-sensing application with high sensitivity and reuse

Two-dimensional (2D) Janus materials have raised considerable attention from the scientific community because of their asymmetric structure and distinctive physical characteristics. Here, we theoretically study the surface gas adsorption effects on the monolayer MoSiGeN4 (MSGN) due to its high carrier mobility and tunable electronic properties. The results show that the built-in electric field in MSGN results in lower adsorption energies on the Si-side than that on the Ge-side. Additionally, the Si-side of MSGN exhibits higher sensitivity to NO2 detection, and the recovery time and conductivity of NO2 adsorption on MSGN are found to be 1.92 × 10−9 s and 138 k/(S × m−1), respectively. Particularly, the Si-side MSGN-based sensors have higher sensitivity for gas detection. This finding provides possibilities for gas sensors with selectivity and sensitivity based 2D Janus monolayers.

Pt-Doped HfS2 Monolayer as a Novel Sensor and Scavenger for Dissolved Gases (H2, CO2, CH4, and C2H2) in Transformer Oil: A Density Functional Theory Study.

Detecting the types and concentrations of dissolved gases in insulating oil by resistivity-type sensors is an extremely effective means for diagnosing faults in an oil-immersed transformer. However, further breakthroughs and innovations are needed in gas-sensitive materials for preparing high-performance resistivity-type sensors. In this investigation, the application possibility of using Pt-doped HfS2 (Pt-HfS2) as gas-sensitive materials for the detection of dissolved H2, CO2, CH4, and C2H2 in oil has been verified by analyzing the adsorption energy (Ead), differential charge density (DCD), density of states (DOS), frontier molecular orbital, and desorption time based on density functional theory (DFT). The outcomes suggest that the band gap of HfS2 is obviously narrowed after doping Pt at the position of the bridge between the S and Hf atoms, resulting in a significant increase in the conductivity of HfS2. The low adsorption energy implies that there is only weak physical adsorption between Pt-HfS2 and CO2 (-0.783 eV). In contrast, the highly hybridized atomic orbitals of Pt with H2, CH4, and C2H2 indicate that strong chemical adsorption reactions occur. Two-dimensional Pt-HfS2 as a gas sensor has a great monitoring performance for CH4 at 298 K (room temperature). This research serves as theoretical guidelines for probing the application potential of Pt-HfS2 in fault diagnosis and predictive maintenance of an oil-immersed transformer.

Light metal decorated graphene-like Si2BN monolayers as hydrogen storage media: A DFT investigation

The hydrogen storage properties of an alkali metal (Li, Na, K) or alkaline earth metal (Be, Mg, Ca) decorated Si2BN monolayer were studied based on first-principles calculations. The study indicated that these metal atoms can be stably bonded on both sides of the Si2BN monolayer, but without promoting agglomeration. Compared with the original structure, the metal-decorated Si2BN monolayer exhibited significantly enhanced physical adsorption for H2 molecules. Furthermore, the Li, Na, Be and Ca-decorated Si2BN monolayers exhibited a high gravimetric density ranging from 7.1 to 11.7 wt% and a suitable adsorption energy range from −0.11 to −0.27 eV. In contrast, the K and Mg-decorated Si2BN monolayers were not suitable for practical applications due to their low adsorption energy (−0.07 eV) and poor gravimetric density (4.6 wt%). In particular, the Li-decorated Si2BN monolayer showed the highest hydrogen storage gravimetric density (11.7 wt%), whilst the Be-decorated Si2BN monolayer showed the closest desorption temperature (319 K) to room temperature. These findings provide theoretical insights into the excellent hydrogen storage properties of this novel graphene-like monolayer material after metal decoration.