Gibbs Free Energy Of Adsorption Research Articles

Thermodynamic Insights of the Molecular Interactions of Dopamine (Neurotransmitter) with Anionic Surfactant in Non-Aqueous Media.

This study was aimed at establishing the interactions prevailing in an anionic surfactant, sodium dodecyl sulfate, and dopamine hydrochloride in an alcoholic (ethanol) media by using volumetric, conductometric, and tensiometric techniques. Various methods were utilized to estimate the critical micelle concentration (cmc) values at different temperatures. The entire methods yielded the same cmc values. The corresponding thermodynamic parameters viz. the standard free energy of micellization (Gmico), enthalpy of micellization (Hmico), and entropy of micellization (Smico) were predicted by applying the pseudo-phase separation model. The experimental density data at different temperatures (298.15 K, 303.15 K, 308.15 K, and 313.15 K) were utilized to estimate the apparent molar volumes (Vϕo) at an infinite dilution, apparent molar volumes (Vφcmc) at the critical micelle concentration, and apparent molar volumes (ΔVφm) upon micellization. Various micellar and interfacial parameters, for example, the surface excess concentration (Γmax), standard Gibbs free energy of adsorption at the interface (ΔGoad), and the minimum surface area per molecule (Amin), were appraised using the surface tension data. The results were used to interpret the intermolecular interactions prevailing in the mixed systems under the specified experimental conditions.

Morphological engineering coupled with electronic engineering accelerates H2 production at the high current density

The insufficient exposure of catalyst active sites and high adsorption energy barrier of intermediates (H*) on the Ni surface are the main reasons for its lack of hydrogen evolution activity under high current. However, developing non noble metal hydrogen evolution electrocatalysts with stable activity under high current density is key to achieving large-scale industrial H2 production. Herein, a tungsten-doped dendritic nickel-copper array on copper mesh (W-NiCuarray/CM) is prepared by combining microscopic morphology control and atomic scale electron control strategies. Benefiting from the unique dendritic morphology and excellent electronic structure, the electrocatalyst exhibits outstanding hydrogen evolution reaction (HER) performance under high current densities. In particular, it requires a low overpotential of 257 and 349 mV at −500 and −1000 mA cm−2, respectively, which surpasses the state-of-the-art commercial Pt/C. Characterization and density functional theory (DFT) further reveal that Cu and W control the electronic structure, and the active center Ni obtains the appropriate d-band center; thus, the optimal Gibbs free energy (ΔGH*) of hydrogen adsorption can be gained. Overall, this study combines morphology engineering and electronic control engineering to provide an idea for the development of advanced nonprecious metal electrocatalysts applied for industrial hydrogen production.

Composition Engineering Opens an Avenue Toward Efficient and Sustainable Nitrogen Fixation

In this work, we open an avenue toward rational design of potential efficient catalysts for sustainable ammonia synthesis through composition engineering strategy by exploiting the synergistic effects among the active sites as exemplified by diatomic metals anchored graphdiyne via the combination of hierarchical high‐throughput screening, first‐principles calculations, and molecular dynamics simulations. Totally 43 highly efficient catalysts feature ultralow onset potentials (|Uonset| ≤ 0.40 V) with Rh‐Hf and Rh‐Ta showing negligible onset potentials of 0 and −0.04 V, respectively. Extremely high catalytic activities of Rh‐Hf and Rh‐Ta can be ascribed to the synergistic effects. When forming heteronuclears, the combinations of relatively weak (such as Rh) and relatively strong (such as Hf or Ta) components usually lead to the optimal strengths of adsorption Gibbs free energies of reaction intermediates. The origin can be ascribed to the mediate d‐band centers of Rh‐Hf and Rh‐Ta, which lead to the optimal adsorption strengths of intermediates, thereby bringing the high catalytic activities. Our work provides a new and general strategy toward the architecture of highly efficient catalysts not only for electrocatalytic nitrogen reduction reaction (eNRR) but also for other important reactions. We expect that our work will boost both experimental and theoretical efforts in this direction.

Investigating the Influence of Aromatic Counterions on the Micellar Structure and Aggregation Behavior of Morpholinium-Based Surface-Active Ionic Liquids in an Aqueous Solution.

Two morpholinium-based surface-active ionic liquids (SAILs) with aromatic counterions were synthesized, namely, n-dodecyl-n-methylmorpholinium salicylate [C12mmor][Sal] and n-dodecyl-n-methylmorpholinium 3-hydroxy-2-naphthoate [C12mmor][3-h-2-n], and explored their aggregation behavior in aqueous solutions systematically. Electrical conductivity, small-angle neutron scattering (SANS), surface tension (ST), and UV-vis spectroscopy measurements were employed to determine various thermodynamic, micellar, and interfacial parameters, like the degree of counterion binding (β), critical micelle concentration (CMC), minimum area per molecule (Amin), surface excess concentration (Γmax), standard Gibbs free energy of adsorption (ΔGad0), aggregation number (Nagg), standard Gibbs free energy of micellization (ΔGm0), standard enthalpy of micelle formation (ΔHm0), and the standard entropy of micellization (ΔSm0) in an aqueous solution. Incorporating the aromatic counterions favors significantly excellent micellization properties over conventional halogenated SAILs such as [C12mmor][Br]. SANS analysis revealed that upon changing the counterion from salicylate to 3-hydroxy-2-naphthoate, the structure changed from prolate ellipsoidal micelles to large unilamellar vesicles. Also, increasing the concentration in the case of [C12mmor][Sal] resulted in a lower aggregation number.

Trisurethane functionalized sulfonamide based polymeric sorbent: Synthesis, surface properties and efficient mercury sorption from wastewater

In this study, trisurethane modified sulfonamide based polymeric adsorbent was prepared starting from reaction with chlorosulfonated poly (styrene) (PS) beads and tris(hidroxymethyl) aminometane. Hydroxyl functions of the adsorbent were reacted with butyl isocyanate in the presence of dibutyltin dilaurate as a catalyst at 60 0C for 48 h to obtain tris urethane functional polymeric adsorbent (PS-TUR). Spectroscopic and morphological characterizations of the polymeric adsorbents were carried out using scanning electron microscopy (SEM-EDX), infrared spectrophotometry (FTIR), XPS and analytical methods.The surface properties of PS-TUR were investigated for the first time with the inverse gas chromatography technique at infinite dilution before adsorption studies. The dispersive surface energy of adsorbent was determined according to the method of Schultz (55.54–61.73 mJ m−2) and Dorris-Gray (57.70–67.03 mJ m−2). Adsorption enthalpy and Gibbs free energy were calculated according to this technique and it was determined that the adsorption was exothermic and spontaneous. As a result of the analyzes made with this technique, it was determined that the PS-TUR adsorbent surface was acidic (KD/KA=0.27<1) and optimum conditions (pH: 7, dose: 0.10 g) were determined for the effective adsorption of Hg (II) ions. Surface acidity-basicity behavior of sorbent was determined by isoelectric point (IEP: 6.20) and pHpzc (5.81) analyses.Batch adsorption studies of the PS-TUR adsorbent were carried out as a function of adsorbent dosage, pH, initial metal ion concentration (0.0025–0.1000 mol/L), and kinetically. After determination of optimum adsorbent dosage was found as 100 mg, mercury sorption capacity of PS-TUR adsorbent was found as 511.50 mg g−1 adsorbent.Desorption studies were carried out using glacial acetic acid and studies demonstrated that PS-TUR adsorbent is regenerable and can be successfully used for four adsorption–desorption cycles without significant loss its capacity.Also, PS-TUR adsorbent shows selectivity with high sorption capacity towards mercury as compared to other metal ions.

Synthesis, physical properties and cytotoxic assessment of ester-terminated gemini imidazolium surfactants

Ester-functionalized gemini imidazolium amphiphiles appended with different spacers have been developed. The desired structures were confirmed using mass spectroscopy and NMR techniques. With the help of tensiometry, conductometry, and spectrofluorometry, the investigated amphiphiles have been characterized for a variety of physical properties including Gibbs free energy of adsorption (ΔG0ads), C20 (surfactant concentration required to reduce the surface tension of the solvent by 20 mN•m−1), maximum surface excess (Ʈmax), critical micelle concentration (cmc), Gibbs free energy of the micellization (ΔG0mic) and Amin (minimum surface area/molecule). Dynamic light scattering (DLS) measurements were taken to examine aggregate size distribution and zeta potential. Thermal decomposition temperature of investigated amphiphiles was determined from thermogravimetric analysis (TGA) analysis. By using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, the toxicity of examined amphiphiles towards the C6 glioma cell line was assessed. The physicochemical study of these surfactants revealed that varying spacer length considerably affects the properties.

Ni-CeO2 Heterostructure Promotes Hydrogen Evolution Reaction via Tuning of the O-H Bond Length of Adsorbed Water at the Electrolyte/Electrode Interface.

Understanding the properties and structure of reactant water molecules at the electrolyte solution/electrode interface is relevant to know the mechanisms of hydrogen evolution reaction (HER). However, this approach has rarely been implemented due to the elusive local microenvironment in the vicinity of the catalyst. Taking the Ni-CeO2 heterostructure immobilized onto carbon paper (Ni-CeO2 /CP) as a model, the dynamic behavior of adsorbed intermediates during the reaction was measured by in situ surface-enhanced infrared absorption spectroscopy with attenuated total reflection configuration (ATR-SEIRAS). Theoretical calculations are used in combination to comprehend the potential causes of increased HER activity. The results show that the O-H bond of adsorbed water at the electrolyte solution/electrode interface becomes longer for promoting the dissociation of water and accelerating the kinetically slow Volmer step. In addition, forming the Ni-CeO2 heterostructure interface optimizes the hydrogen adsorption Gibbs free energy, thus increasing HER activity. Therefore, the Ni-CeO2 /CP electrode exhibits remarkably low HER overpotentials of 37 and 119 mV at 10 and 100 mA cm-2 , which are close to commercial Pt/C (16 and 102.6 mV, respectively).

Modulation of the electronic structure of Co2P by Mo, Fe co-doping for efficient urea electrolysis

Hydrogen production by urea splitting not only plays an energy-saving role in the production of hydrogen energy, but also can purify wastewater containing urea, which has great advantages compared with hydrogen production by water splitting. In this study, Mo, Fe co-doped bifunctional Co2P electrodes were prepared through hydrothermal and moderate-temperature phosphating methods. Under the synergistic effect of bimetallic cations, the electronic structure of Co2P is effectively modulated, thus showing excellent electrochemistry performance in urea splitting. In the electrolyte solution of 1 M KOH and 0.5 M urea, the potential of urea oxidation reaction (UOR) is 1.26V, 1.316 V and 1.336V for driving current density of 10, 50 and 100 mA cm−2, and the overpotential of hydrogen evolution reaction (HER) is 194 mV, 244 mV and 268 mV for driving current density of 10, 50 and 100 mA cm−2. The overall urea electrolysis only requires a voltage of 1.415 V and 1.686 V to drive a current density of 10 and 50 mA cm−2, which is one of the best catalytic activities reported to date. The experimental results show that the increased activity is assigned to the rapid charge transfer, the exposure of more active sites and the improved conductivity due to the doping of bimetallic ions. Density functional theory (DFT) demonstrates that the prepared Mo, Fe co-doped Co2P electrodes has the smallest Gibbs free energy for hydrogen adsorption compared with Fe co-doped Co2P electrodes. This work laid a new foundation for the synthesis of bimetallic cation-doped transition metal phosphide (TMP) for urea-assisted water splitting.

Triangular nanosheet arrays of O-doped Co/Fe disulfides as highly efficient electrocatalysts for the hydrogen evolution reaction

The development of inexpensive and efficient electrocatalysts is of significance for the hydrogen evolution reaction (HER) involved in water splitting. In this work, we report triangular nanosheet arrays of O-doped Co/Fe disulfides (labelled O-(CoFe)S2-x-y, in which x is the Fe concentration and y is the sulfurization temperature) grown on carbon cloth (CC). With the Co-MOF as precursor, Fe was introduced by ligand exchange, and O-doped metal sulfides were achieved via calcination followed by sulfurization. An optimized sample of CC@O-CoFeS-0.025–500 exhibited an outstanding electrocatalytic HER performance, and it showed strong durability (≥ 24 h) and a very low overpotential of 105 mV at a current density of 10 mA cm−2 (η10 = 105 mV) in 0.5 M H2SO4. The interspaces-rich nanosheet array morphology of O-CoFeS-0.025–500 enabled maximum exposure of the electrocatalytically active sites. O doping effectively modulated the electronic structure, promoted charge redistribution of the catalyst and significantly increased the intrinsic catalytic activity. Density functional theory (DFT) calculations indicated that the Co atoms in pure CoS2 were the catalytically active sites, and the Gibbs free energy for hydrogen adsorption (ΔGH*) was 0.38 eV. Most notably, Fe/O codoping changed the active sites of O-CoFeS-0.025–500 from Co to S with a markedly reduced ΔGH* of 0.22 eV at the S sites. This work provides a novel perspective for designing outstanding electrocatalysts through element doping to realize highly effective water splitting and produce hydrogen.

Analysis of the influence of high-entropy oxide optimized electrolyte on the electrochemical performance of iron chromium flow batteries

The electrochemical performance of iron chromium flow batteries was improved by optimizing the electrolyte with high-entropy oxides. The influence of high-entropy oxide content in the electrolyte on the electrochemical performance of iron chromium flow batteries was studied and analyzed. Due to the synergistic effect of conductivity and electrochemical activity, the flow batteries exhibit better electrochemical performance when the electrolyte doping amount is 1 wt%. When the current density is 160 mAcm-2, the capacity of the assembled flow battery after optimizing the electrolyte is 210 mAhL-1, and the capacity after 100 cycles is 187 mAhL-1. From the calculation of adsorption energy and Gibbs free energy, it can be seen that the adsorption free energy of CuMn2O4 for iron ions is -151.256 J/mol, which greatly promotes the rate of redox reaction in the iron chromium flow batteries. This work effectively improves the electrochemical performance of iron chromium flow batteries, and further provides theoretical guidance and data support for the application of high-entropy oxides in flow batteries.

Electrochemical, surface analysis, computational and anticorrosive studies of novel di-imine Schiff base on X65 steel surface

The inhibitory effect of di-imine-SB namely ((N1Z, N4E)-N1, N4-bis (4 (dimethylamino) benzylidene) butane 1,4-diamine) on X65-steel in 1 M HCl has been investigated experimentally and theoretically. The electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and weight loss outcomes display the anticorrosion properties of “di-imine- SB”. The inhibitory efficiency exceeds 90% at the optimal concentration of 1 × 10–3 M “di-imine- SB”. The metal surface was examined further using scanning electron microscope (SEM) and energy dispersive X-ray (EDX). The effectiveness of the di-imine-SB is returned into its adsorption on X65-steel surface and found in agreement with Langmuir adsorption isotherm. According to the standard Gibbs free energy of adsorption ({Delta G}_{ads}^{^circ }), di-imine-SB adsorption tends to be chemical rather than physical, it increases the activation energy ({mathrm{E}}_{a}) of metal dissolution reaction and makes it hard to occur. The PDP data suggested anodic and cathodic type of the di-imine-SB inhibitor. Meanwhile, increasing the resistance of X65-steel to 301 Ω cm2 after adding 1 mM of di-imine-SB confirms its protective effect. Whereas, the positive value of the fraction of electron transference (ΔN, 0.746), confirms the affinity of di-imine-SB to share electrons to the partially filed 3d-orbital of Fe forming strong protective film over X65-steel surface. Aided by Monte Carlo (MC) simulation, the calculated adsorption energy (Eads) suggests excessive adsorption affinity of di-imine-SB on metal surface over the corrosive chlorides and hydronium ions. A good correlation between the theoretical hypothesis and the experimental inhibition efficiency has been achieved. The comparative study showed the superior of the di-imine-SB as potential corrosion inhibitor compared with those reported before. Finally, global reactivity descriptors; electron affinity (A), ionization potential (I), electronegativity (χ), dipole moment (µ), global hardness (eta), electrophilicity index and, Fukui indices were also calculated and found well correlated to the reactivity of di-imine-SB.

Investigation of Hexylamine Adsorption on Gold in Perchloric Acid

The adsorption of hexylamine at the solution–gold interface in 1 M HClO4 in the presence of 0.1 M Fe2+ and 0.1 Fe3+ was studied by potentiodynamic, chronoamperometric and EIS methods. The main kinetic characteristics of the oxidation-reduction reaction iron ions (exchange current density, transfer coefficient, diffusion coefficients of iron ions) were determined. It was shown that the physical adsorption of hexylamine on gold can be described by the Dhar–Flory–Huggins isotherm. The values of the adsorption constant and the Gibbs free adsorption energy were obtained. A comparison of the free adsorption energy at these interfaces with the interaction energies of hexylamine and water molecules, and hexylamine molecules with each other was carried out. It was shown that hexylamine adsorption at all of these interfaces is due mainly to the hydrophobic effect of the interaction of hexylamine and water molecules.

Surface and interfacial properties of poly(methyldiallylammonium chloride): Effect of hydrophobic pendant and synergism (KI) on corrosion of C1018CS in 15% HCl

BackgroundIn the current investigation, a dicationic surfactant made of poly(methyldiallylammonium chloride) (PMDAAC) was tested for its ability to suppress corrosion of C1018 carbon steel (C1018 CS) in a 15% HCl (acidizing) solution. MethodsWeight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), linear polarization resistance (LPR), scanning electron spectroscopy (SEM), energy dispersive X-ray (EDX), atomic force microscope (AFM), and density functional theory (DFT). Significant findingsWeight loss tests show that PMDAAC has no significant inhibitory potential for the C1018CS/15% HCl system, as seen by its inhibition efficiency (IE) of 76.57% at 50 ppm concentration. However, adding 5 mM KI significantly increases the% IE of PMDAAC from 76.57% to 95.26% at the same concentration. A similar trend in the boost of% IE of PMDAAC from 85.33% to 99.28% and 83.28% to 98.42% was observed through PDP and EIS studies, respectively. PDP study showed that the current density (icorr) values kept decreasing with increasing PMDAAC concentration. PMDAAC behaves as a mixed- and interface-type inhibitor, being able to retard the progress of both anodic and cathodic reactions. EIS analysis showed that the values of charge transfer resistance (Rct) kept increasing with increasing inhibitor concentration. The adsorption isotherm study suggests that PMDAAC becomes effective by adsorbing on the C1018 CS surface, and its adsorption follows the Langmuir isotherm. A high value of 6.37 × 105 L mol-1 corresponds to the equilibrium constant for the adsorption process (Kads), indicating very strong adsorption of PMDAAC onto C1018 CS. PMDAAC was found to chemisorb onto the metal surface, as confirmed by the Gibbs free energy of adsorption (ΔGads∘) found to be – 43.76 kJ mol−1. The adsorption of PMDAAC on the C1018CS surface was confirmed by SEM and EDX studies. The improvement in surface morphology and alteration in elemental alignment in the presence of PMDAAC demonstrate the adsorption mode of corrosion mitigation. Lastly, the interaction of PMDAAC and its constituting components were described using the DFT method.

Fluorinated Ni‐O‐C Heterogeneous Catalyst for Efficient Urea‐Assisted Hydrogen Production

AbstractConstructing multiple heterogeneous structures allows for improving the electrocatalytic activity of NiO by incorporating multiple active sites. Unfortunately, the poor conductivity of NiO makes efficient charge transfer within the heterogeneous structures difficult, thereby inhibiting the improvement of its intrinsic activity. Herein, F‐doped NiO/Ni@C heterogeneous catalyst (F‐NiO/Ni@C) is fabricated via a new organic‐inorganic hybrid approach, showing both advanced hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) activity. The targeted F‐doping increases electron delocalization, and facilitates electron transfer from Ni to NiO at the nano‐interfaces. This interphase synergy provides ready‐to‐use F‐NiO active sites, allowing F‐NiO/Ni@C to achieve optimum H* adsorption Gibbs free energy for HER and a lower energy barrier for UOR. As a result, the as‐configured F‐NiO/Ni@C || F‐NiO/Ni@C cell requires an ultra‐low cell voltage of 1.37 V to achieve 10 mA cm−2 in alkaline media (with 0.3 M urea), outperforming the state‐of‐the‐art benchmark Pt/C|| RuO2 cell (1.45 V). This study reveals the positive impact of anion doping on interphase synergy and provides useful guidelines for designing monometallic catalysts for UOR as well as hydrogen generation.

Heterojunction regulates the function of coral like NiCoP for efficient hydrogen evolution reaction

The development of earth abundant electrocatalysts for high performance hydrogen evolution reaction (HER) is highly desirable in energy conversion system. Transition metal phosphide has been exploited to promote electrochemical performance due to its unique heterointerface, outstanding conductivity, and a wide pH range tolerance. Herein, we employ a facile hydrothermal approach to build a heterojunction interface modulated coral-like NiCoP electrocatalyst with favorable crystalline surface, minimal charge transfer resistance, and excellent electron transfer for outstanding HER. In alkaline media, the optimum NiCoP electrocatalyst demonstrates excellent HER performance with an overpotential of 215 mV and Tafel slope of 82 mV dec−1 at 10 mA cm−2. This benefits from the formation of heterojunction with exposed active sites, redistributed electrons and altered coordination environment. The combined experimental results and density functional theory (DFT) investigations demonstrate that heterojunction interfaces are beneficial for lowering the Gibbs free energy of hydrogen adsorption (ΔGH∗), hence boosting HER dynamics process. This study presents a feasible approach for the preparation of low-cost, high-efficiency NiCoP electrocatalysts for HER, which is particularly appealing for practical applications.

Electric double layer-mediated polarization field for optimizing photogenerated carrier dynamics and thermodynamics

Photocatalytic hydrogen evolution efficiency is limited due to unfavorable carrier dynamics and thermodynamic performance. Here, we propose to introduce electronegative molecules to build an electric double layer (EDL) to generate a polarization field instead of the traditional built-in electric field to improve carrier dynamics, and optimize the thermodynamics by regulating the chemical coordination of surface atoms. Based on theoretical simulation, we designed CuNi@EDL and applied it as the cocatalyst of semiconductor photocatalysts, finally achieved a hydrogen evolution rate of 249.6 mmol h−1 g−1 and remained stable after storing under environmental conditions for more than 300 days. The high H2 yield is mainly due to the perfect work function, Fermi level and Gibbs free energy of hydrogen adsorption, improved light absorption ability, enhanced electron transfer dynamics, decreased HER overpotential and effective carrier transfer channel arose by EDL. Here, our work opens up new perspectives for the design and optimization of photosystems.

S, Fe dual doped and precisely regulated CoP porous nanoneedle arrays for efficient hydrogen evolution at 3 A cm−2

Transition metal phosphides (TMPs) have been proved as promising catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, CoP has a strong hydrogen adsorption energy, resulting in a slow Heyrovsky step in the HER. Herein, the solid phase FeS is ionized into S and Fe ions and doped into cobalt precursor during the hydrothermal process based on the precipitation dissolution equilibrium principle, and the doping strategy precisely regulated the atomic ratio of metal/P. The optimized S, Fe-CoP@IF one-dimensional porous nanoneedles structure exhibit excellent HER performance, which only required 82.3 mV and 200.1 mV to achieve 100 mA cm−2 and 3 A cm−2 together with high currents stability for 100 h. It also has better OER performance, with 260 mV reaching 100 mA cm−2. Further simulated industrial test for S, Fe-CoP@IF in alkaline anion-exchange membrane (AEM) cells show that only 1.75 V is required to attain 500 mA cm−2. Density functional theory (DFT) calculations confirmed that the dual-doping further modulates the electronic structure of CoP, reduces the Gibbs free energy for hydrogen adsorption. This work provides the possibility to further improve the catalytic activity of cobalt phosphide and apply it to industrial applications.

Activating and optimizing the In-Plane interface of 1 T/2H MoS2 for efficient hydrogen evolution reaction

Implanting the octahedral phase (1 T) into the hexagonal phase (2H) of the molybdenum disulfide (MoS2) matrix is considered one of the effective methods to enhance hydrogen evolution reaction (HER) performances of MoS2. In this paper, hybrid 1 T/2H MoS2 nanosheets array was successfully grown on conductive carbon cloth (1 T/2H MoS2/CC) via facile hydrothermal method and the 1 T phase content in 1 T/2H MoS2 is regulated to gradually increase from 0 % to 80 %. 1 T/2H MoS2/CC with 75 % 1 T phase content exhibits optimal HER performances. The DFT calculation results show that S atoms in 1 T/2H MoS2 interface exhibit the lowest hydrogen adsorption Gibbs free energies (ΔGH*) compared with other sites. The improvement of HER performances are primarily attributed to activating the in-plane interface regions of the hybrid 1 T/2H MoS2 nanosheets. Furthermore, the relationship between 1 T MoS2 content in 1 T/2H MoS2 and catalytic activity was simulated by a mathematical model, which shows that the catalytic activity presents a trend of increasing and then decreasing with the increase of 1 T phase content.

Evolution hydrothermal aging resistance mechanism study of zirconium and manganese doped CeO2 catalysts in soot catalytic combustion based on low Miller indices crystal surface effect

The thermogravimetric analysis (TGA) experiments were carried out to reveal the mechanism of Zr and Mn doping on catalytic activity of CeO2 catalyst both fresh and after hydrothermal aging, and the lattice morphology and valence changes were characterized by means of Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H2-temperature programmed reduction (H2-TPR). Density functional theory (DFT) and molecular thermodynamics calculations were applied to investigate the change in catalytic activity, crystal surface energy and crystal morphology caused by hydrothermal aging. The maximum reaction rate temperature of fresh Mn/CeO2 (389 °C) is similar to that of CeO2 (371 °C) and lower than that of Zr/CeO2 (447 °C), but the catalytic performance of CeO2 decreases more severely after hydrothermal aging. The catalyst crystals show different degrees of crystal surface migration after hydrothermal aging, which leads to the reduction of Ce3+/Ce4+ ratio and the active sites shift. DFT calculations indicate that the doping of Zr and Mn reduces the surface energy of the low Miller indices surface and increases the oxygen vacancy formation energy, leading to better thermal stability and lower catalytic activity. The Zr and Mn doping also changes the adsorption energy and Gibbs free energy of H2O, which dominates the migration of (1 1 1) to (1 1 0) and (1 0 0) in the vapor environment. The crystal surface migration mechanism of CeO2 catalysts doped with Zr and Mn induced by H2O molecules at high temperature obtained in this study can provide a valuable addition to the regeneration of CeO2 catalysts in the after-treatment systems of diesel engines.

Anchoring Ru nanoparticles on Ti3C2Tx for accelerated alkaline hydrogen evolution reaction: The effect of electronic metal-support interaction

Electrocatalytic hydrogen evolution reaction (HER) in the alkaline media is a promising strategy for energy conversion. Nevertheless, the sluggish kinetics of alkaline HER hinders its commercial application. Electronic metal-support interaction (EMSI) is an efficient approach to regulate the electronic state of active sites and enhance the electrocatalytic HER performance. Hence, we demonstrate an efficient alkaline HER catalyst comprising Ruthenium nanoparticles (Ru NPs) homogeneously anchored on Ti3C2Tx (Ru-Ti3C2Tx), resulting in the formation of EMSI effect between Ru and Ti3C2Tx. Spectroscopy characterizations and theoretical calculations demonstrate that EMSI facilitated the charge transfer from Ru NPs to Ti3C2Tx. The regulation of local electron density on Ru NPs directly influenced hydrogen adsorption Gibbs free energy (ΔGH*), which optimized the adsorption of hydrogen intermediates (H*) on Ru NPs and promoted the formation of H2 molecules. Therefore, the obtained 5 % Ru-Ti3C2Tx catalyst displayed an outstanding HER performance with the overpotential of 46 mV and 60 mV at 10 and 200 mA·cm−2 in 1.0 M KOH, respectively. Furthermore, the cathode presented excellent stability during 20 h long-term measurements. This study presents some recommendations and guidance for constructing Ru-based catalysts to accelerate HER kinetics in alkaline media.