Reaction Energy Barrier Research Articles

Highly Stable Lanthanide-Organic Frameworks Based on {Ln6O8} Clusters with Photocatalytic Reduction of CO2 to CO.

Metal-organic frameworks (MOFs) with adjustable structures, diverse chemical functionalities, and excellent CO2 capture ability have shown important potential application in the photocatalytic reduction of CO2 to valuable fuel to curb the energy crisis. In this work, a series of new isostructural lanthanide-organic frameworks based on hexanuclear {Ln6O8} clusters, {(DMA)2 [Ln6(μ3-OH)8(H2O)6(SBTC)3]}n (Ln-MOFs, Ln = Eu, Dy, Gd, Tb, Yb; H4SBTC = 5,5'-(ethene-1,2-diyl) di-isophthalic acid; DMA = dimethylamine cation) were synthesized by the solvothermal method. Ln-MOFs were metal-organic frameworks formed by {Ln6(μ3-OH)8} clusters and poly(carboxylic acid) ligands H4SBTC, which exhibited excellent photocatalytic properties for the reduction of CO2 to CO. Among these Ln-MOFs, the production rate of photocatalytic reduction of CO2 to CO by Eu-MOF was 663.00 μmol·h-1·g-1 and the selectivity reached 94.2%, utilizing [Ru(bpy)3]Cl2·6H2O as photosensitizers. Experimental characterizations and density functional theory (DFT) calculations unveiled that the effective charge separation, strong CO2 binding affinity, weak H2O adsorption energy, as well as low reaction energy barriers for the *COOH intermediates over Eu-MOF play an important role in possessing superior photoactivity. This study provides insights into the field of Ln-MOF materials for efficient photocatalytic CO2 reduction and conversion applications.

Platinum Compound on Gold–Magnesia Hybrid Structure: A Theoretical Investigation on Adsorption, Hydrolysis, and Interaction with DNA Purine Bases

Cisplatin-based platinum compounds are important clinical chemotherapeutic agents that participate in most tumor chemotherapy regimens. Through density-functional theory calculations, the formation and stability of the inorganic oxide carrier, the mechanisms of the hydrolysis reaction of the activated platinum compound, and its binding mechanism with DNA bases can be studied. The higher the oxidation state of Pt (II to IV), the more electrons transfer from the magnesia–gold composite material to the platinum compound. After adsorption on the composite carrier, 5d←2p coordination bonds of Pt-N are strengthened. For flat and oblique adsorption modes of cisplatin, there is no significant difference in the density of states of the gold and magnesium oxide film, indicating the maintenance of the heterojunction structural framework. However, there are significant changes in the electronic states of cisplatin itself with different adsorption configurations. In the flat configuration, the band gap width of cisplatin is larger than that of the oblique configuration. The Cl-Pt bond range in the Pt(III) compound shows a clear charge reduction on the magnesia film, indicating the Cl-Pt bond is an active site with the potential for decomposition and hydrolysis. The substitution of chloride ions by water can lead to hydrolysis products, enhancing the polarization of the composite and showing strong charge separation. The hydrolysis of the free platinum compound is endothermic by 0.309 eV, exceeding the small activation energy barrier of 0.399 eV, indicating that hydrolysis of this platinum compound is easily achievable. ADME (absorption, distribution, metabolism, and excretion) prediction parameters indicate that hydrolysis products have good ESOL (Estimated SOLubility) solubility and high gastrointestinal absorption, consistent with Lipinski’s rule. During the coordination reaction process, there are significant changes in the distribution of frontier molecular orbitals, with the HOMO (highest occupied molecular orbital) of the initial state primarily located on the purine base, providing the possibility for electron transfer to the empty orbitals of the platinum compound in the LUMO (lowest unoccupied molecular orbital). The HOMO and HOMO-1 of the transition state and product are mainly distributed on the platinum compound, indicating clear electron transfer and orbital rearrangement. The activation energy barrier for the purine coordination reaction with the hydrolysis products is reduced to 0.61 eV, and the dipole moment gradually decreases to 6.77 Debye during the reaction, indicating a reduction in the system’s charge separation and polarization. This contribution is anticipated to provide a new theoretical clue for developing inorganic oxide carriers of platinum compounds.

Cucurbituril‐Manipulated Supramolecular Electrodes for Highly Active and Stable (Photo)electrocatalytic Oxidation Reactions

AbstractThe robust immobilization and activity regulation of molecular catalysts on solid electrodes have remained persistent challenges in catalysis. Herein, cucurbituril (CB[7]) acts is first demonstrated as a bifunctional medium to firmly immobilize molecular catalyst CoTMPyP onto various metal oxide electrodes, including TiO2, BiVO4, α‐Fe2O3, and WO3, through host‐guest and electrostatic interactions. This approach not only secures stable attachment of the catalyst but also optimizes its electronic structure and catalytic activity. The CB[7]‐mediated supramolecular electrodes exhibit exceptional performance in electrocatalytic oxygen evolution reaction (OER), ethanol oxidation reaction, hydrazine oxidation reaction, and photoelectrocatalytic water oxidation. For instance, TiO2‐CB[7]‐CoTMPyP electrode achieves a turnover frequency (TOF) of 5.30 s−1 at an overpotential of 600 mV for OER, and BiVO4‐CB[7]‐CoTMPyP photoanode delivers a water oxidation photocurrent density of 6.00 mA cm−2 at 1.23 V versus RHE under simulated solar irradiation. Mechanistic studies reveal CB[7] plays a critical role beyond merely serving as a linker: it enhances charge accumulation around the cobalt sites, promotes reactants adsorption at these sites, reduces reaction energy barrier, and accelerates charge transfer rate, thereby significantly boosting catalytic activity. This work provides a groundbreaking pathway for the design and fabrication of cost‐effective, high‐performance molecular‐based electrodes for (photo)electrocatalytic reactions.

Optimizing s‐p Orbital Overlap between Sodium Polysulfides and Single‐Atom Indium Catalyst for Efficient Sulfur Redox Reaction

P‐block metal carbon‐supported single‐atom catalysts (C‐SACs) have emerged as a promising candidate for high‐performance room‐temperature sodium‐sulfur (RT Na‐S) batteries, due to their high atom utilization and unique electronic structure. However, the ambiguous electronic‐level understanding of Na‐dominant s‐p hybridization between sodium polysulfides (NaPSs) and p‐block C‐SACs limits the precise control of coordination environment tuning and electro‐catalytic activity manipulation. Here, s‐p orbital overlap degree (OOD) between the s orbitals of Na in NaPSs and the p orbitals of p‐block C‐SACs is proposed as a descriptor for sulfur reduction reaction (SRR) and sulfur oxidation reaction (SOR). Compared to NG and NG‐supported InN4 (NG‐InN4) SACs, the nitrogen‐doped graphene‐supported InN5 (NG‐InN5) SACs show the largest s‐p OOD, demonstrating the weakest shuttle effect and the lowest reaction energy barriers in both SRR and SOR. Accordingly, the designed catalysts allow the Na‐S pouch batteries to retain a high capacity of 490.7 mAh g‐1 at 2 A g‐1 with a Coulombic efficiency of 96% at a low electrolyte/sulfur (E/S) ratio of 4.5 μl. This work offers an s‐p orbital overlap descriptor describing the interaction between NaPSs and p‐orbital‐dominated catalysts for high‐performance RT Na‐S batteries.

Mn Doping at High‐Activity Octahedral Vacancies of γ‐Fe2O3 for Oxygen Reduction Reaction Electrocatalysis in Metal‐Air Batteries

γ‐Fe2O3 with the intrinsic cation vacancies is an ideal substrate for heteroatom doping into the highly active octahedral sites in spinel oxide catalysts. However, it is still a challenge to confirm the vacancy location of γ‐Fe2O3 through experiments and obtain enhanced catalytic performance by preferential occupation of octahedral sites for heteroatom doping. Here, a Mn‐doped γ‐Fe2O3 incorporated with carbon nanotubes catalyst was developed to successfully achieve preferential doping into highly active octahedral sites by employing γ‐Fe2O3 as the precursor. Further, the vacancy in γ‐Fe2O3 was only located on octahedral sites rather than tetrahedral ones, which was first proved by direct experimental evidence through the clarification doping sites of Mn. Notably, the catalyst shows outstanding activity towards oxygen reduction reaction with the half‐wave potential of 0.82 V and 0.64 V vs. reversible hydrogen electrode in alkaline and neutral electrolytes, respectively, as well as the maximum power density of 179 mWcm−2 and 403 mWcm−2 for Mg‐air batteries and Al‐air batteries, respectively. It could be attributed to the synergistic effect of the doping Mn on octahedral sites and the substrate γ‐Fe2O3 along with the modification of the adsorption/desorption properties for ORR oxygen‐containing intermediates as well as the optimization of the reaction energy barriers.

Alloying Strategy Regulating Size and Electronic Structure of Mo0.25Nb0.75Se2 to Achieve High‐Performance Lithium–Sulfur Batteries

The utilization of catalysts in lithium−sulfur batteries has proven to be an efficacious avenue for enhancing the kinetics of polysulfide conversion. Specially, the size and electronic structure of catalysts play a pivotal role in harnessing the active sites and intrinsic catalysis activity. Outstanding MoSe2 and NbSe2 are selected from 16 universal transition metal selenides based on the proposed binary descriptor. Then, an alloying strategy is devised to prepare Mo0.25Nb0.75Se2 flakelets for further improvement of the intrinsic catalysis. The integration of density functional theory calculations and electrochemical analysis demonstrates that alloying Mo with Nb can regulate the surface energy and indexes of band match and lattice mismatch, thereby enabling Mo0.25Nb0.75Se2 to possess a small size, suitable adsorption energy and low reaction energy barrier. This optimization enhances the catalysis of sulfur reduction/evolution reaction and the reversible deposition/stripping of lithium. Consequently, an assembled Ah‐level pouch cell is realized with dramatic cycle stability. With the electrolyte/sulfur ratio of 2.36 μL mg S–1, the cell can deliver a high energy density of up to 505.4 Wh kgtotal−1. This work pioneers a universal strategy for sculpting the geometric configurations and electronic structures of catalysts, to achieve enhanced catalytic activity and precise interpretation of structure−activity relationships.

Catalytic pyrolysis mechanism of tetrabromobisphenol A by calcium oxide: A density functional theory study

In this paper, the mechanisms of catalytic pyrolysis of tetrabromobisphenol A (TBBPA) by calcium oxide (CaO) were studied through density functional theory methods. The results indicate that the phenolic hydroxyl group of TBBPA is the preferred site for CaO to extract protons, and the generated anion further transforms into 2,6-dibromophenol via demethylation and hydrogen transfer reactions. The reaction activity of CaO with hydrogen bromide is relatively high, with an energy barrier of 133.2 kJ/mol. CaO produces calcium ions, which combine with bromine ions to form calcium bromide to achieve the purpose of fixing bromine. In addition, the participation of calcium ions results in the OH bond being easier to crack, which further lowers the reaction energy barrier of keto-enol tautomerism reactions H2O produced during catalytic pyrolysis also has an obvious catalytic effect, and the energy barrier of the keto-enol tautomerism reaction decreased from 309.1 kJ/mol to 150.6 kJ/mol with the participation of H2O.

Copper slag based catalytic material was prepared using a one-pot method to efficiently activate of peroxymonosulfate for degradation of carbamazepine

Smelt slag-based environmental catalytic materials offer a sustainable and valuable approach to solid waste management. In this study, a novel peroxymonosulfate (PMS) catalyst (MCT-2) was prepared from copper slag (MCT-1) by a non-calcined method. Subsequently, the MCT/PMS-AOP catalytic system was established. The copper slag, mainly composed of Si, Ca, Mg, Fe and O, was converted into MCT-2 by hydrothermal treatment, NaOH etching and edta-2na-induced crystallization, and finally, the molecular self-loading of MCT was achieved by the "one-pot method" under hydrothermal conditions. MCT-2 exhibits a layered surface morphology and CaFeO3 phase. In the MCT-2/PMS system, the dominant reactive oxygen species (ROSs) generated were SO4•− and HO•. The performance of the system was evaluated using CBZ as a simulated pollutant and actual river water as a carrier, and it was found that MCT-2/PMS degraded CBZ, BPA, DCF and ATZ up to 99%. Further mechanistic studies showed that MCT-2 has relatively high catalytic activity and the lowest reaction energy barrier compared with similar materials. The easy availability of raw materials, environmentally friendly preparation method, and high degradation efficiency make MCT/PMS-AOP have a broad application prospect.

MOF-derived phase-selective synthesis of ln2O3 with appropriate surface atomic arrangement for CO2 photoreduction

Crystal phase engineering emerges as a powerful strategy to enhance photocatalytic activity, yet controlled phase-selective synthesis and phase-dependent performance understanding remain challenging. In this study, we introduce a novel method for synthesizing phase-engineered In2O3 via the pyrolysis of metal–organic frameworks (MOFs). We demonstrate that the functional groups and pyrolysis temperatures of MOFs are critical for phase-selective synthesis. Specifically, pyrolysis of MIL-68(ln)–NH2 at optimal temperatures yields In2O3 with rhombohedral (rh-In2O3), cubic (c-In2O3), and rhombohedral/cubic heterophase (rh/c-In2O3) structures. Our photocatalytic CO2 reduction tests reveal that c-In2O3 outperforms rh-In2O3 and rh/c-In2O3, achieving a CO production rate of 29.19 μmol g-1h−1 with 94.47 % selectivity. Spectroscopic and theoretical analyses show that c-In2O3 has superior charge transfer efficiency and lower reaction energy barriers, particularly for the rate-determining *CO intermediate, which exhibits a lower Gibbs free energy on its surface. This work provides a significant advancement in optimizing photocatalytic CO2 reduction efficiency through precise phase engineering, underscoring the vital role of phase control in enhancing catalytic performance.

Iron-Induced vacancy and electronic regulation of nickle phosphides for ampere-level alkaline water/seawater splitting

Rational design of non-precious metal catalysts can accelerate the oxygen evolution reaction (OER) kinetics. Herein, inspired by theoretical analysis, in-situ Fe-doped Ni2P/Ni12P5 with rich P vacancies (Fe-NiPx) is designed and constructed, in which the production of P vacancies is induced by Fe doping. Relevant characterizations confirm that the Fe doping and P vacancies can co-adjust the crystal and electronic structures, thereby optimizing the reconstruction behavior and improving the intrinsic activity of reconstructed-derived Ni(Fe)OOH. As a result, it exhibits excellent OER activity with overpotentials of 256 and 276 mV to achieve the current density of 100 mA cm−2 in 1 M KOH solutions and alkaline seawater, respectively. Furthermore, the Fe-NiPx electrode only requires 1.861 and 1.889 V to drive the 1.0 A cm−2 overall water and seawater splitting, respectively, and maintains stable output as high as 1000 h. Also, to demonstrate the great application potential, green energy-to-hydrogen systems are established. Electrochemical tests and theoretical calculations reveal that reconstructed-Fe-NiPx facilitates the OER kinetics under the adsorbate evolution mechanism (AEM) pathway, with optimized adsorption free energies of intermediates and reduced reaction energy barriers. This work provides new insights into efficient water and seawater splitting through in-situ heteroatom doping and vacancy engineering.

Hydrogenation Reaction Mechanisms on Ni-Doped MoS2 Catalysts: A Density Functional Theory Study of Sulfur Edge Engineering and Coregulated Electronic Effects.

Precise modulation of local interatomic interactions affecting the electronic structure is an important method to control the catalytic activity and reaction pathways. In this study, we focused on the hydrogenation reaction of naphthalene and employed density functional theory calculations to investigate the specific influence of electronic effects triggered by the coregulation of Ni and sulfur edge engineering on the hydrogenation performance of Ni-doped MoS2 at different edge sulfur coverages (Ni-MoS2-X-θs). Our findings reveal that the interaction between Ni and S in the catalyst matrix material modifies the local electronic structure surrounding the sulfur atoms in the active site. Notably, Ni doping facilitates significant electron transfer, altering the charge and the electronic states at the catalyst edge. This, in turn, affects the adsorption capacity and reactivity of the catalyst, thereby reducing the energy barrier of the hydrogenation reaction. Furthermore, we paid particular attention to the modulation of catalytic activity and reaction pathways under the Eley-Rideal (E-R) mechanism. Interestingly, the sulfur coverage exhibited a nonlinear relationship with the adsorption and activation properties of the probe molecule. Typically, changes in the Mo edge sulfur coverage probability of Ni-MoS2-X-θs have a greater impact on the activation properties. Through comprehensive studies, we demonstrated that both compositional and structural factors must be considered when tailoring the catalytic performance. Importantly, adjusting the ratio of marginal sulfur atoms to metal atoms to 1:1 can effectively enhance the catalytic activity. This study provides valuable insights into the electronic effects regulating the hydrogenation reaction activity of MoS2-based catalysts. It also opens the way for the rational design of novel hydrogenation catalysts, offering a new strategy for optimizing the catalytic performance.

Candle flame generated Co and Fe single atoms supported in soot as novel host for lithium-sulfur batteries with excellent electrochemical performance

By simply introducing metal salts into paraffin, Co and Fe single atoms dispersed in candle soot (CS) can be directly collected from the flame of home-made candles without any byproducts. STEM, XRD and XANES analysis demonstrate that Co and Fe exist in single atom state. The prepared Co-CS and Fe-CS, with high specific area and excellent sulfur loading capability, can be used as innovative host for cathode to assemble Li-S pouch cells, and exhibit excellent electrochemical performance with higher specific capacities (approximately 1250 mAh/g at 0.1 C with 7.5 mg/cm² sulfur loading) and improved cycling stability (retaining about 63 % of capacity after 50 cycles) than bare CS host. Meanwhile, density functional theory (DFT) calculations demonstrate that Fe-CS/Co-CS decrease the energy barriers of conversion reactions from Li2S8 to Li2S due to the increased binding energy between Co-CS/Fe-CS and LiPSs, therefore effectively mitigating the polysulfides shuttle effect. Such a strategy holds promise for practical cell-level designs in Li-S batteries.

B and P dual sites co-modified g-C3N4 p–n homojunction for photocatalytic CO2 reduction coupled with metronidazole oxidation

The limited active sites and sluggish reaction kinetics greatly restrict the photocatalytic redox activity for CO2 reduction coupled with metronidazole (MNZ) oxidation. Herein, the electron rich P and electron deficient B were synergistically anchored on graphitic carbon nitride for constructing BPCN p − n homojunction with isolated B and P redox dual − sites, which exhibits an excellent CO yield rate of 3.811 μmol g−1h−1 coupled with outstanding MNZ removal rate of 92.60 %. The improvement of photocatalytic redox performance was mainly attributed to two aspects: On the one hand, the construction of p − n homojunction effectively accelerated the separation and migration of carriers; On the other hand, the B and P redox dual − sites availably reduced the reaction energy barrier of CO2 reduction and MNZ oxidation, respectively. Besides, the dual − functional coupled reaction system realized the full utilization of photogenerated charges. This work not only offers new insight for designing efficient p − n homojunction with redox double sites, but also confirms the potential application for congenerous environment renovation and energy conversion.

Assessing the Effect of a Schwarz P Surface on the Oxygen Electroreduction Performance of Porous Single-Atom Catalysts.

The surface curvature of catalysts has a decisive impact on their catalytic performance. However, the influence of a negative-Gaussian-curvature surface on the catalytic performance of porous catalysts has remained unexplored due to the lack of suitable samples. Bicontinuous-structured porous structures can serve as ideal models, but they are known as "Plumber's nightmare" due to their highly difficult preparation. Here, using metal-organic frameworks as the precursor and polymer cubosomes as the template, a bicontinuous mesoporous Fe single-atom catalyst (named bmFeSAC) with a Schwarz P surface is synthesized. The bmFeSAC catalyst has a large specific surface area of 916m2g-1 and uniformly distributed Fe-N4 active sites with a 1.80wt.% Fe content. The continuous channels enabled high utilization efficiency of the Fe-N4 catalytic sites, while the negative-Gaussian-curvature surface enabled low reaction energy barrier. As an electrocatalyst of the oxygen reduction reaction, bmFeSAC delivered a high half-wave potential of 0.931V versus. RHE in alkaline electrolyte, reaching the leading level among those of the reported state-of-the-art electrocatalysts. Furthermore, the bmFeSAC-based Zn-air batteries exhibited excellent performance, demonstrating the potential application of bmFeSAC. This study revealed that a bicontinuous-structured porous structure can improve catalytic activity by increasing the utilization ratio of catalytic sites and, more importantly, by regulating the electronic structure of catalyst surfaces through the negative-Gaussian-curvature.

Synergistic Regulation of Bidirectional Conversion of LiPSs and Li2S Using Anthraquinone as a Redox Mediator.

Lithium-sulfur (Li-S) batteries are strong contenders as energy storage options in the next-generation, primarily because of their potential for delivering high energy densities. Nonetheless, their widespread commercialization faces several obstacles, including sluggish sulfur redox kinetics, the insulating properties of the Li2S discharge product, and significant reaction energy barriers. In this work, anthraquinone (AQ) was introduced as a redox mediator and incorporated onto Co-doped carbon materials through π-π interactions. The results showed that synergistic effect between AQ and Co atoms facilitated the bidirectional conversion of lithium polysulfides (LiPSs) and Li2S. During charging, AQ lowered the reaction energy barrier for Li2S oxidation and thereby enhanced the reversibility of sulfur redox reactions. Density functional theory (DFT) calculations showed that AQ-Li2Sx exhibits a lower energy for the lowest unoccupied molecular orbital (LUMO) and a higher energy for the highest occupied molecular orbital (HOMO). Experimental results demonstrated that an impressive initial discharge specific capacity of 1290 mAh g-1 was achieved by the fabricated S@AQ/Co-N-C electrode at 0.1 C. After 600 cycles at 1 C, it retained 64% of this capacity and exhibited a minimal 0.06% capacity decay rate per cycle.

Experimental and density functional theory calculation study on the NO2 adsorption and reduction by KOH activated biochar

Biochar prepared from waste biomass as an adsorption and reduction material can effectively decrease decrease nitrogen dioxide (NO2) emissions. This work aims to select suitable materials to prepare biochar and improve its ability to adsorb and reduce NO2. In this study, the process of adsorption and reduction of NO2 by biochar and the effect of KOH activation on these reactions are studied by using fixed-bed reactor and density functional theory calculation. Experimental results indicate a positive correlation between the adsorption and reduction capabilities of biochar for NO2 and its specific surface area and surface oxygen groups. The biochar sample prepared by pyrolysis at 800 ℃ with the addition of 3 wt% KOH solution exhibits the highest adsorption capacity, likely due to the catalytic role of potassium (K) in the adsorption-reduction reaction. It is worth noting that the theoretical calculation results confirm this point. The K atom primarily facilitates the breaking of the N-O bond in NO2 and the desorption of the NO molecule on biochar through van der Waals forces, thereby lowering the reaction energy barrier. Thermodynamic and kinetic analyses further confirm these findings. This study has a new understanding of the mechanism of NO2 adsorption and reduction of by KOH activated biochar, which provides experimental basis and theoretical guidance for the application of this technology.

Understanding the Negative Apparent Activation Energy for Cu2O and CoO Oxidation Kinetics at High Temperature near Equilibrium

The pairs of Cu2O/CuO and CoO/Co3O4 as the carriers of transferring oxygen and storing heat are essential for the recently emerged high-temperature thermochemical energy storage (TCES) system. Reported research results of Cu2O and CoO oxidation kinetics show that the reaction rate near equilibrium decreases with the temperature, which leads to the negative activation energy obtained using the Arrhenius equation and apparent kinetics models. This study develops a first-principle-based theoretical model to analyze the Cu2O and CoO oxidation kinetics. In this model, the density functional theory (DFT) is adopted to determine the reaction pathways and to obtain the energy barriers of elementary reactions; then, the DFT results are introduced into the transition state theory (TST) to calculate the reaction rate constants; finally, a rate equation is developed to describe both the surface elemental reactions and the lattice oxygen concentration in a grain. The reaction mechanism obtained from DFT and kinetic rate constants obtained from TST are directly implemented into the rate equation to predict the oxidation kinetics of Cu2O without fitting experimental data. The accuracy of the developed theory is validated by experimental data obtained from the thermogravimetric analyzer (TGA). Comparing the developed theory with the traditional apparent models, the reasons why the latter cannot appropriately predict the true oxidation characteristics are explained. The reaction rate is jointly controlled by thermodynamics (reaction driving force) and kinetics (reaction rate constant). Without considering the effect of the reaction driving force, the negative apparent activation energy of Cu2O oxidation is obtained. However, for CoO oxidation, the negative apparent activation energy is still obtained although the effect of the reaction driving force is considered. According to the DFT results, the activation energy of the overall CoO oxidation reaction is negative, but the energy barriers of the elementary reactions are positive. Moreover, according to the first-principle-based rate equation theory, the pre-exponential factor in the kinetic model is dependent on the partition function ratio and decreases with the temperature for the Cu2O and CoO oxidation near equilibrium, which results in the apparent activation energy being slightly lower than the actual value.

Electrochemical Nitrate Reduction to Ammonia on AuCu Single‐Atom Alloy Aerogels under Wide Potential Window

AbstractElectrocatalytic nitrate reduction to ammonia (NO3RR) is very attractive for nitrate removal and ammonia production in industrial processes. However, the nitrate reduction reaction is characterized by intense hydrogen competition at strong reduction potentials, which greatly limits the Faraday efficiency at strong reduction potentials. Herein, we reported an AuxCu single‐atom alloy aerogels (AuxCu SAAs) with three‐dimensional network structure with significant nitrate reduction performance of Faraday efficiency (FE) higher than 90 % over a wide potential range (0 ~ −1 V RHE). The FE of the catalyst was close to 100 % at a high reduction potential of −0.8 VRHE, accompanying with NH3 yield reaching 6.21 mmol h<M−>1 cm<M−>2. More importantly, the catalyst maintained a long‐term operation over 400 h at 400 mA cm<M−>2 for the NO3RR using a continuous flow system in a H‐cell. Experimental and theoretical analysis demonstrate that the catalyst can lower the energy barrier for the hydrogenation reaction of *NO2, leading to a rapid consumption of the generated *H, facilitate the hydrogenation process of NO3RR, and inhibit the competitive HER at high overpotentials, which efficiently promotes the nitrate reduction reaction, especially in industrial applications.

Electrochemical Nitrate Reduction to Ammonia on AuCu Single-Atom Alloy Aerogels under Wide Potential Window.

Electrocatalytic nitrate reduction to ammonia (NO3RR) is very attractive for nitrate removal and ammonia production in industrial processes. However, the nitrate reduction reaction is characterized by intense hydrogen competition at strong reduction potentials, which greatly limits the Faraday efficiency at strong reduction potentials. Herein, we reported an AuxCu single-atom alloy aerogels (AuxCu SAAs) with three-dimensional network structure with significant nitrate reduction performance of Faraday efficiency (FE) higher than 90 % over a wide potential range (0 ~ -1 V RHE). The FE of the catalyst was close to 100 % at a high reduction potential of -0.8 VRHE, accompanying with NH3 yield reaching 6.21 mmol h<M->1 cm<M->2. More importantly, the catalyst maintained a long-term operation over 400 h at 400 mA cm<M->2 for the NO3RR using a continuous flow system in a H-cell. Experimental and theoretical analysis demonstrate that the catalyst can lower the energy barrier for the hydrogenation reaction of *NO2, leading to a rapid consumption of the generated *H, facilitate the hydrogenation process of NO3RR, and inhibit the competitive HER at high overpotentials, which efficiently promotes the nitrate reduction reaction, especially in industrial applications.

Deliquescence of damaged rock salt under high humidity and its effect on inter-seasonal salt cavern gas storage

Salt cavern underground gas storages (UGSs) are ideal for mitigating demand fluctuations in gas resources such as hydrogen, helium, and natural gas. Rock salts surrounding the cavern are chronically exposed to high humidity during the inter-seasonal operation, and the effect of its deliquescence is worth investigating. In this study, deliquescence rates of damaged rock salt at the humidity of UGSs was measured. Undamaged rock salts deliquesce slowest. The rate increases by 532 % as the strain reaches 2.40 %. This ratio decreases to 372 % when rocks enter plastic deformation stages. Cracks and crystal defects in damaged rocks are inferred to accelerate deliquescence by increasing the local relative humidity through the Kelvin effect and lowering reaction energy barriers, respectively. As the crack widens with deformation, imbibed brine inhibits the deliquescence by healing defects and reducing water-salt contact. A subroutine coupling deformation and deliquescence of rock surrounding the cavern was developed. Its application in Jintan, China shows that deliquescence increases the cavern span, intensifying local creep and crack evolution. The volume shrinkage of the cavern increased by 2.80 %, and the safety factor was reduced, but empirical safety criteria were still satisfied. This study helps to assess UGS salt caverns' storage performance more accurately.