Free Energy Change Research Articles

Boosting Solar‐Driven CO2 Conversion to Ethanol via Single‐Atom Catalyst with Defected Low‐Coordination Cu‐N2 Motif

In this paper, we report a high‐performance carbon nitride supported Cu single‐atom catalyst featuring defected low‐coordination Cu‐N2 motif (Cu‐N2‐V). Lead many recently reported photocatalysts and its Cu‐N3 and Cu‐N4 counterparts, Cu‐N2‐V exhibits superior photocatalytic activity for CO2 reduction to ethanol, delivering 69.8 μmol g‐1 h‐1 ethanol production rate, 97.8% electron‐based ethanol selectivity, and a yield of ~10 times higher than Cu‐N3 and Cu‐N4. Revealed by the extensive experimental investigation combined with the DFT calculation, the superior photoactivity of Cu‐N2‐V stems from its unique defected Cu‐N2 configuration. Firstly, Cu in Cu‐N2‐V exist in Cu+/Cu2+ dual valence states, although predominantly in Cu+. The Cu+ sites support CO2 activation and the Cu+/Cu2+ sites are conducive for strong *CO adsorption and subsequent *CO‐*CO dimerization enabling C‐C coupling. Secondly, the Cu sites in Cu‐N2‐V are rich in electrons and thus highly active. Together they dictate the rate‐determining step on CO2 photoreduction to ethanol and lower the Gibbs free energy change. Furthermore, the defected configuration also promotes light adsorption and charge separation efficiency. Collectively, these make Cu‐N2‐V an effective and high‐performance catalyst for solar‐driven CO2 conversion to ethanol. This study also reveals the valence state change of Cu in Cu‐N2‐V during the CO2 photoreduction reaction.

Boosting Solar-Driven CO2 Conversion to Ethanol via Single-Atom Catalyst with Defected Low-Coordination Cu-N2 Motif.

In this paper,we report a high-performance carbon nitride supported Cu single-atom catalyst featuring defected low-coordination Cu-N2 motif (Cu-N2-V). Lead many recently reported photocatalysts and its Cu-N3 and Cu-N4 counterparts, Cu-N2-V exhibits superior photocatalytic activity for CO2 reduction to ethanol, delivering 69.8 μmol g-1 h-1 ethanol production rate, 97.8% electron-based ethanol selectivity, and a yield of ~10 times higher than Cu-N3 and Cu-N4. Revealed by the extensive experimental investigation combined with the DFT calculation, the superior photoactivity of Cu-N2-V stems from its unique defected Cu-N2 configuration. Firstly, Cu in Cu-N2-V exist in Cu+/Cu2+ dual valence states, although predominantly in Cu+. The Cu+ sites support CO2 activation and the Cu+/Cu2+ sites are conducive for strong *CO adsorption and subsequent *CO-*CO dimerization enabling C-C coupling. Secondly, the Cu sites in Cu-N2-V are rich in electrons and thus highly active. Together they dictate the rate-determining step on CO2 photoreduction to ethanol and lower the Gibbs free energy change. Furthermore, the defected configuration also promotes light adsorption and charge separation efficiency. Collectively, these make Cu-N2-V an effective and high-performance catalyst for solar-driven CO2 conversion to ethanol. This study also reveals the valence state change of Cu in Cu-N2-V during the CO2 photoreduction reaction.

Hierarchical-hollow architecture NiSe2 nanosheets for overall water splitting

Electrolytic water splitting (EWS), regarded as a sustainable and promising strategy for hydrogen production, has received huge attention in recent years. However, the practical application of EWS is greatly hindered by the sluggish kinetics of the oxygen evolution reaction (OER). Herein, we proposed an efficient strategy for the synthesis of hierarchical hollow nickel selenide with significant HER and OER electrocatalytic activity. The as-synthesized NiSe2 possesses low overpotential of ∼85 mV at the current density of 10 mA/cm2 for the HER in 0.5 M H2SO4 and ∼270 mV for OER in 1 M KOH. Importantly, when employed into full water splitting on membrane electrode assembly, it merely requires an ultralow voltage of 1.73 V to achieve the current density of 1 A/cm2, outperforming most of the reported other Ni/Ni-Se based structures. Density Functional Theory (DFT) simulations confirm that the hierarchical hollow NiSe2 structure facilitates the reduction of the Gibbs free energy change of H- and O-containing intermediates in the HER/OER process, which promotes the formation of intermediates and thus accelerates the catalytic kinetics. This work offers an important structure engineering route to develop high catalytic performance materials and sheds light on the promotion of electrocatalytic activity for clean energy utilization.

Growth of L asparagine monohydrate doped potassium dihydrogen phosphate semiorganic crystals and its structural, thermal and optical properties

A novel semiorganic crystal is harvested by doping organic amino acid L asparagine monohydrate (LAM) with inorganic compound Potassium dihydrogen phosphate (KDP) by adopting slow evaporation method. Rietveld refinement of the XRD data was performed and the structural study exhibits single phase nature of the LAM doped KDP (LAM-KDP) crystals with a slight decrease in c-axis of the unit cell parameters. Other crystallographic parameters such as crystallite size and strain were also evaluated. The interaction of LAM with KDP was studied from FT-IR analysis by detecting functional groups. The constituting elements of the crystal were identified by energy dispersive X-ray (EDX) analysis. Etching study has been employed to study surface morphology of these crystals. From UV–vis transmittance data, optical band gap and different optical constants like Urbach energy, dielectric constants, electrical and optical conductivities were evaluated. Optical transparency of the LAM-KDP crystals is observed to increase. The third order nonlinear susceptibility χ(3) and nonlinear refractive index n2 of the grown crystals have been predicted using empirical Miller's rule. The value of χ(3) has increased from 1.87 × 10−13 esu to 4.29 × 10−13 esu due to LAM doping. Change in enthalpy (ΔH), change in Gibb's free energy (ΔG) and activation energy Ea during chemical reaction were calculated by thermogravimetric analysis (TGA). Thermal decomposition characteristics of the crystals were analyzed by differential scanning calorimetry (DSC). The high transparency of LAM-KDP crystals in the entire visible spectrum and larger values of nonlinear susceptibility χ(3) and nonlinear refractive index n2 make the synthesized crystal applicable for NLO and optoelectronic devices applications.

Chitin extraction from crab shells and synthesis of chitin @metakaolin composite for efficient amputation of Cr (VI) ions

The present research study combines chitin from shrimp waste with the oxide-rich metakaolin. Metakaolin is a blend of mixed oxides rich in silica and alumina with good adsorbent properties. The chitin@metakaolin (CHt@M.K.) composite was synthesized and characterized using FTIR, SEM, TGA, XRD and XPS techniques. Cr(VI) removal studies were compared for chitin and CHt@M.K. through adsorption. It was found that the adsorption capacity of CHt@M.K. is 278.88 mg/g, almost double that of chitin, at pH 5.0 in just 120 min of adsorption. Isotherm models like Langmuir, Freundlich, Temkin and Dubinin–Radushkevich were investigated to comprehend the adsorption process. It was revealed that Langmuir adsorption isotherm is most suitable to elucidate Cr(VI) adsorption on CHt@M.K. The adsorption kinetics indicate that pseudo first order was followed, indicating that the physisorption was the process that limited the sorption process rate. The positive enthalpy change (20.23 kJ/mol) and positive entropy change (0.083 kJ/mol K) showed that the adsorption process was endothermic and more random at the solid-liquid interface. The negative free energy change over entire temperature range was an indicator of spontaneity of the process. Apart from all these, the non-covalent interactions between Cr(VI) and composite were explained by quantum calculations based models.

KINETICS AND THERMODYNAMIC ASSESSMENT OF RICE HUSK IN AN INERT ATMOSPHERE AS A FEEDSTOCK FOR ALTERNATIVE FUEL PRODUCTION

The utilisation of rice husk as a feedstock for alternative fuel production is an area of growing interest due to its abundance and potential as a renewable energy source. This study reports investigation of kinetics and thermodynamics of rice husk pyrolysis in an inert atmosphere. Experimental analysis, including proximate, ultimate, structural composition and thermogravimetric analyses (TGA), were conducted to determine the proxanal, ultanal, chemical composition and pyrolysis characteristics of rice husk under inert conditions. Kinetics of the pyrolysis process was evaluated using distributed activation energy model (DAEM) while thermodynamic parameters such as activation energy (E A), changes in enthalpy (ΔH), entropy (ΔS),and Gibbs free energy (ΔG) were computed to provide insights into the reaction mechanisms. The feedstock exhibited ash content, fixed carbon, volatile matter, and higher heating value on dry basis of 13.56wt%, 16.37wt%, 70.07wt% and 15.22MJ/kg respectively while the result of ultimate analysis showed carbon, hydrogen, nitrogen, sulphur and oxygen content of 40.95, 5.67, 0.22, 0.09 and 52.17wt%. The chemical composition result (water extractives-free) indicated cellulose, hemicellulos and lignin content of 39.12, 17.56 and 22.43 wt%. The kinetics analysis revealed that the pyrolysis process followed a single-order reaction mechanism and irreversible, suggesting that the pyrolysis reactions proceed in a direction that favors the formation of products. The average E A, ΔH, ΔS and ΔG required for the pyrolysis reactions was established to be 140.56 kJ/mol, 137.00 kJ/mol, -135.25 J/mol and 222.38 kJ/mol respectively. The comprehensive assessment of the feedstock affirms its suitability for alternative fuel production towards a greener energy landscape.

Configuration entropy and thermodynamics phase transition of black hole in [formula omitted] gravity

Starting from a d−dimensional black hole (BH) in f(R) gravity, we analyzed the effect of modified gravity on critical point parameters, the difference in number densities, and configuration entropy during the BH phase transition phenomenon. From our investigations, consistent results with charged AdS BH are obtained that is holographic dual of van der Waal’s fluid and hence the BH in modified gravity. The thermodynamic pressure, temperature, and free energy are affected by f(R) gravity. The difference in the number densities of molecules (small and large BHs) and configuration entropy are investigated as a function of reduced temperature (τ̃). The difference in the number densities of BH molecules in f(R) gravity decreases with the increase in τ̃, whereas, Scon increases monotonically and becomes a concave function with the increase in space–time dimensions. The relation between the difference in the number density of BH molecules and space–time dimensions (d) decreases with the increase in dimension d. Finally, using our results, the laws of BH Physics are also discussed.

DFT and TD-DFT Studies of D-π-A Organic Dye Molecules with Different Spacers for highly Efficient Reliable Dye Sensitized Solar Cells.

This study focuses on six D-π-A systems, utilizing diverse π-spacers as bridges. Comprehensive analysis through Density Functional Theory (DFT) and Time-dependent Functional Theory (TD-DFT) methods at B3LYP using 6-31G (d.p) basis set explores geometrical, electrical, optical, photovoltaic, and absorption properties. EHOMO, ELUMO, and energy gap (Egap), for all of these dyes have been determined and discussed using ground state optimization. TD-DFT calculates optical properties, unveiling enhanced excitation energies and HOMO-LUMO energy levels, indicative of improved electron injection and dye regeneration processes. Examination of energy gap, open-circuit voltage (VOC), free energy change (ΔGinject), light harvesting efficiency (LHE), and absorption spectra reveals D4 dye's lower Egap and robust absorption in the visible spectrum. Molecular tailoring emerges as a promising technique for optimizing D-π-A sensitizer design, offering potential advancements in DSSCs applications.

CAIMD Simulations Guided Design of Atomic Praseodymium Doping In–Bi Nanofibers for High‐Energy‐Efficiency CO2 Electrolysis to Formate in Ultra‐Wide Potential Window

AbstractThe electrochemical CO2 reduction reaction (ECO2RR) has emerged as a promising technology for achieving carbon neutralization. Even though considerable efforts are dedicated to gain deep insight into the understanding of ECO2RR on a mechanism level through density functional theory (DFT) studies, effects of solvent molecules and temperature have long been neglected by conventional DFT calculations as a consequence of limitations in current technologies and computational power of supercomputers. Under this context, the lack of comprehensive understanding over the energy changes in the reaction derived from the only concern on free energy changes between reaction intermediates have arouse an urgent call for exploring feasible calculation options toward generalized theoretical study. Here, a systematic mechanism study is provided toward ECO2RR via constrained ab initio molecular dynamics (cAIMD) simulations, in which the effects of solvent water molecules and temperature are taken into consideration to guide the synthesis of single‐atom alloy (SAA) catalyst. Consequently, the resultant Pr0.05/InBi achieves a maximum Faradic efficiency (FE) of 96.4% and an energy efficacy (EE) of 59.41% for formate. This work offers a novel approach to the design and screening of SAA catalysts, presenting foreseeable future in accelerating the industrial application process of ECO2RR.

Subnanometric Pt-Ga alloy clusters confined within Silicalite-1 zeolite for n-hexane dehydrogenation

Dehydrogenation of light naphtha followed by catalytic cracking into high-value end products can meet the high demand in the world’s petrochemical market. In this work, at attempting synthesis of novel catalysts for hexane dehydrogenation, a series of bimetallic Pt-Ga clusters encapsulated within Silicalite-1 (S-1) catalysts were synthesized using the ligand-protected direct H2 reduction method. The reduced Pt-Ga@S-1-H catalysts comprised restricted ultra-fine Pt-Ga alloys with an average size 0.86–0.95 nm, mainly corresponding to the Pt3 clusters with coordinate number 1.5–2.1. Ga doping significantly improved the catalytic stability, depending on the Ga content, which ranged from 0.02 to 0.27 wt%. As confirmed by the XPS and EXAFS analysis, after the Ga addition, electron transfer occurred between the Pt-Ga alloys and the skeleton oxygen in zeolite, stabilizing the Pt clusters on the zeolite, thereby inhibiting the growth of Pt crystals. During the n-hexane dehydrogenation, the 0.40Pt0.04 Ga@S-1-H catalyst exhibited a hexene selectivity of 87.1 %, achieving a hexene formation rate of 101.4 molhexene∙gPt-1∙h−1 at 550 °C with a WHSV of 90 h−1. After 1000 min of reaction, this best catalyst experienced only slight deactivation with a deactivation constant of 0.066 h−1. The catalytic activity remained almost unchanged after consecutive five cycles of H2 regeneration. DFT calculation using the synchronous structural models showed that the Gibbs free energy changes (−ΔG) for the first three steps of hexane dehydrogenation over the 0.4Pt0.04 Ga@S-1-H catalyst were much lower than those obtained on the 0.4Pt/S-1-H catalyst, suggesting that the introduction of Ga energetically favored the hexane dehydrogenation.

Bioinspired axial S-coordinated single-atom cobalt catalyst to efficient activate peroxymonosulfate for selective high-valent Co-Oxo species generation

The efficient activation and selective high-valent metal-oxo (HVMO) species generation remain challenging for peroxymonosulfate (PMS)-based advanced oxidation processes (PMS-AOPs) in water purification. The underlying mechanism of the activation pathway is ambiguous, leading to a massive dilemma in the control and regulation of HVMO species generation. Herein, bioinspired by the bio-oxidase structure of cytochrome P450, the axial coordination strategy was adopted to tailor a single-atom cobalt catalyst (CoN4S-CB) with an axial S coordination. CoN4S-CB high-selectively generated high-valent Co-Oxo species (Co(IV)=O) via PMS activation. Co(IV)=O demonstrated an ingenious oxygen atom transfer (OAT) reaction to achieve the efficient degradation of sulfamethoxazole (SMX), and this allowed robust operation in various complex environments. The axial S coordination modulated the 3d orbital electron distribution of the Co atom. Density functional theory (DFT) calculation revealed that the axial S coordination decreased the energy barrier for PMS desorption and lowered the free energy change (ΔG) for Co(IV)=O generation. CoN4S-PMS* had a narrow d-band close to the Fermi level, which enhanced charge transfer to accelerate the cleavage of O-O and O-H bonds in PMS. This work provides a broader perspective on the activator design with natural enzyme structure-like active sites to efficient activate PMS for selective HVMO species generation.

Interpretation of Hydrogen/Deuterium Exchange Mass Spectrometry.

This paper sheds light on the meaning of hydrogen/deuterium exchange-mass spectrometry (HDX-MS) data. HDX-MS data provide not structural information but dynamic information on an analyte protein. First, the reaction mechanism of backbone amide HDX reaction is considered and the correlation between the parameters from an X-ray crystal structure and the protection factors of HDX reactions of cytochrome c is evaluated. The presence of H-bonds in a protein structure has a strong influence on HDX rates which represent protein dynamics, while the solvent accessibility only weakly affects the HDX rates. Second, the energy diagrams of the HDX reaction at each residue in the presence and absence of perturbation are described. Whereas the free energy change upon mutation can be directly measured by the HDX rates, the free energy change upon ligand binding may be complicated due to the presence of unbound analyte protein in the protein-ligand mixture. Third, the meanings of HDX and other biophysical techniques are explained using a hypothetical protein folding well. The shape of the protein folding well describes the protein dynamics and provides Boltzmann distribution of open and closed states which yield HDX protection factors, while a protein's crystal structure represents a snapshot near the bottom of the well. All biophysical data should be consistent yet provide different information because they monitor different parts of the same protein folding well.

Efficient production of biodiesel from palm fatty acid distillate using a novel hydrochar-based solid acid catalyst derived from palm leaf waste

To combat fuel shortages, pollution, and the exhaustion of natural oil resources, an environmentally friendly alternative to fossil fuels, such as biodiesel, is essential for meeting global transportation demands. A novel heterogeneous acid catalyst for production of biodiesel from low-cost, high free fatty acid feedstocks was synthesized in this study by activating and impregnating hydrochar from palm leaf (PL) waste with H3PO4 and H2SO4. Subsequently, the sulfonated catalyst was utilized for the esterification of palm fatty acid distillate (PFAD). FT-IR, XRD, FESEM, EDX, BET, TGA, and surface acidity methods were employed to characterize the acid catalyst. Using the one-variable-at-a-time (OVAT) technique, the optimized reaction conditions for esterification of PFAD using the hydrochar-based catalyst were 4 wt.% catalyst loading, 353.15 K reaction temperature, 4 h reaction time, and 18:1 methanol: PFAD molar ratio. At these conditions, a maximum biodiesel yield of 93.56% was achieved. The catalyst exhibited excellent reusability and stability throughout five reaction cycles, maintaining biodiesel yields above 80% after each cycle. Analysis of the fuel properties revealed that the biodiesel derived from PFAD met the physiochemical criteria outlined in ASTM D6751, the American biodiesel standard. The kinetic study revealed that the esterification reaction followed pseudo-first-order kinetics with an activation energy (Ea) of 23.70 kJ/mol. Furthermore, the thermodynamic enthalpy (∆H*) and Gibbs' free energy (∆G*) of esterification were 20.9 and 33.41 kJ/mol, respectively, indicating that the reaction was an endothermic and non-spontaneous process.

Evaluating the biomolecular interaction between delamanid/formulations and human serum albumin by fluorescence, CD spectroscopy and SPR: Effects on protein conformation, kinetic and thermodynamic parameters

Delamanid is an anti-tuberculosis drug used for the treatment of drug-resistant tuberculosis. Since delamanid has a high protein bound potential, even patients with low albumin levels should experience high and rapid delamanid clearance. However, the interaction between delamanid and albumin should be better controlled to optimize drug efficacy. This study was designed to evaluate the binding characteristics of delamanid to human serum albumin (HSA) using various methods: fluorescence spectroscopy, circular dichroism (CD), surface plasmon resonance (SPR), and molecular docking simulation. The fluorescence emission band without any shift indicated the interaction was not affected by the polarity of the fluorophore microenvironment. The reduction of fluorescence intensity at 344nm was proportional to the increment of delamanid concentration as a fluorescence quencher. UV-absorbance measurement at the maximum wavelength (λmax, 280nm) was evaluated using inner filter effect correction. The HSA conformation change was explained by the intermolecular energy transfer between delamanid and HSA during complex formation. The study, which was conducted at temperatures of 298K, 303K, and 310K, revealed a static quenching mechanism that correlated with a decreased of bimolecular quenching rate constant (kq) and binding constant (Ka) at increased temperatures. The Ka was 1.75–3.16 × 104M−1 with a specific binding site with stoichiometry 1:1. The negative enthalpy change, negative entropy change, and negative Gibbs free energy change demonstrated an exothermic-spontaneous reaction while van der Waals forces and hydrogen bonds played a vital role in the binding. The molecular displacement approach and molecular docking confirmed that the binding occurred mainly in subdomain IIA, which is a hydrophobic pocket of has, with a theoretical binding free energy of −9.33kcal/mol. SPR exhibited a real time negative sensorgram that resulted from deviation of the reflex angle due to ligand delamanid-HSA complex forming. The binding occurred spontaneously after delamanid was presented to the HSA surface. The SPR mathematical fitting model revealed that the association rate constant (kon) was 2.62 × 108s−1M−1 and the dissociation rate constant (koff) was 5.65 × 10−3 s−1M−1. The complexes were performed with an association constant (KA) of 4.64 × 1010 M−1 and the dissociation constant (KD) of 2.15 × 10−11 M. The binding constant indicated high binding affinity and high stability of the complex in an equilibrium. Modified CD spectra revealed that conformation of the HSA structure was altered by the presence of delamanid during preparation of the proliposomes that led to the reduction of secondary structure stabilization. This was indicated by the percentage decrease of α-helix. These findings are beneficial to understanding delamanid-HSA binding characteristics as well as the drug administration regimen.

Selecting phenolics by means of thermodynamics for scavenging free radicals in camellia oil induced by heating

Phenolics have been employing as promising scavengers for free radicals, theoretical calculation is a convenient method for selecting excellent phenolics. In this study, the efficiencies of 33 phenolics scavenging free radicals were confirmed by means of Bond Dissociation Enthalpy (BDE) of active group and Gibbs Free Energy Change (ΔG) of scavenging reaction computed by Quantum Chemical Calculations. Ultimately, the preferable phenolics were picked out for scavenging free radicals in camellia oil induced by heating. These phenolics scavenged free radicals via Hydrogen Atom Transfer (HAT) mechanism. Specifically, (−)-epigallocatechin gallate (EGCG), myricetin and piceatannol performed the top-ranking efficiencies in camellia oil under 120°C for 50 min, with the inhibition ratios of 75.7 ± 4.1%, 72.9 ± 5.4% and 69.4 ± 11.0%, respectively. The results indicated that the efficiencies of phenolics were predominantly affected by the amount of hydroxyl groups attached to aromatic ring and the BDE of O−H bond. In phenolic acids, the hydroxyl group in ortho-position of the active site was in favor of reinforcing the efficiency. In flavonoids, the hydroxyl group in B-ring and the functional groups of C2=C3 and 4-carbonyl in C-ring were prone to elevating the efficiency.

Computational Study of Designed Peptide Analogs against Pseudomonas aeruginosa as a Possible Inhibitor of LptD Membrane Protein

Background: Pseudomonas aeruginosa is a common cause of nosocomial infection worldwide and is responsible for 18-61% of deaths alone. The organism has gained resistance to many known antibiotics and evolved into a multidrug-resistant strain. The LptD outer membrane protein of P. aeruginosa is a special target of interest due to its role in outer membrane biogenesis. Objective: The study aimed to gain an insight into how mutations affect the overall properties of antimicrobial peptides and to identify novel peptide analogs against P. aeruginosa. Methods: The peptide analogs were designed and shortlisted based on physicochemical parameters and estimated free energy change in the current study. The docking studies for wild type and shortlisted peptides were performed against LptD protein of P. aeruginosa. The toxicity, allergenicity, and solubility analyses of peptide analogs with high binding affinity to LptD were also conducted. Results: The molecular docking results indicated that peptide analogs 523M26, 523M29, 523M34, and 523M35 for AP00523 (wild type); 608M12, 608M13, 608M19, 608M31, 608M32, 608M39, and 608M43 for AP00608 (wild type); and 2858M25 for AP02858 (wild type) bound effectively with LptD membrane than their wild types. The toxicity, allergenicity, and solubility analyses revealed all these peptide analogs to be nontoxic, non-allergen, and have good water solubility. Conclusion: The binding energies predicted 523M26, 608M39, and 2858M25 bind effectively to LptD proteins than their wild type. Based on docking analysis, it was further predicted that 608M39 has an estimated binding affinity greater than L27-11, which is a known peptidomimetic inhibitor of the LptD protein.

Bis(dimethylpyrazolyl)-aniline-s-triazine derivatives as efficient corrosion inhibitors for C-steel and computational studies.

4,6-Bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-phenyl-1,3,5-triazin-2-amine (PTA-1), N-(4-bromophenyl)-4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazin-2-amine (PTA-2) and 4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-(4-methoxyphenyl)-1,3,5-triazin-2-amine (PTA-3) were synthesized and characterized. Their corrosion inhibition of carbon C-steel in 0.25 M H2SO4 was studied by electrochemical impedance. The inhibition efficiency (IE%) of triazine was superior due to the cumulative inhibition of triazine core structure and pyrazole motif. Potentiodynamic polarizations suggested that s-triazine derivatives behave as mixed type inhibitors. The IE% values were 96.5% and 93.4% at 120 ppm for inhibitor PTA-2 and PTA-3 bearing -Br and -OCH3 groups on aniline, respectively. While PTA-1 without an electron donating group showed only 79.0% inhibition at 175 ppm. The adsorption of triazine derivatives followed Langmuir and Frumkin models. The values of adsorption equilibrium constant K°ads and free energy change ΔG°ads revealed that adsorption of inhibitor onto steel surface was favoured. A corrosion inhibition mechanism was proposed suggesting the presence of physical and chemical interactions. Density functional theory computational investigation corroborated nicely with the experimental results. Monte Carlo simulation revealed that the energy associated with the metal/adsorbate arrangement dE ads/dN i, for both forms of PTA-2 and PTA-3 with electron donating groups (-439.73 and -436.62 kcal mol-1) is higher than that of PTA-1 molecule (-428.73 kcal mol-1). This aligned with experimental inhibition efficiency results.

Theoretical insights on 3D transition metal anchored poly[5,10,15,20-tetra(4-ethynylphenyl)porphyrin]diyne as highly efficient bifunctional catalyst toward ORR and OER

Searching for highly active oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts is a challenging task in the development of clean energy devices. Herein, by using the poly[5,10,15,20-tetra(4-ethynyl-phenyl)porphyrin]diyne (TEPPD), we designed ORR and OER catalysts by anchoring 3d transition metal into TEPPD (TM@TEPPD, TM = Mn-Zn). Our study indicated that Fe@TEPPD is the best bifunctional catalyst for both ORR and OER. By proposing a proper descriptor, Ni-N3@TEPPD (Ni is only coordinated with three N atoms) is designed and also predicted to be a promising bifunctional catalyst. For Fe@TEPPD, ORR and OER become inactive when the acetylene bond in TEPPD is broken. The surface Pourbaix diagram indicated that on the surface of Fe@TEPPD, ORR and OER can be carried out at the whole pH region due to the high dissolution potential of Fe2+. For Ni-N3@TEPPD, however, the dissolution potential 0.71 V for Ni2+is low. Thus, for Ni-N3@TEPPD, ORR can be carried out only after pH>2.54, while OER is not likely at the whole pH region. This suggested that the conclusions from the free energy changes at URHE=0 and pH=0 could be different when different potentials and pH values are considered.

Highly selective electrocatalytic CO2 reduction to multi-carbon products at CuPd synergistic sites over OD-Cu based catalysts

CO2 reduction is a potential way to kill two birds with one stone by converting greenhouse gas into fuels through clean energy. Cu-based catalysts, with a wide range of products, often have limited selectivity and low activity for specific products. In this study, Cu2O was used as the oxide-derived copper (OD-Cu) substrate, which was loaded with CuPd nanoparticles by using pulsed potential and galvanic replacement. Theoretical calculations revealed that the strong H-affinity Pd sites can reduce the selectivity of formate by stabilizing *COOH and simultaneously lowering the d-band center of neighboring Cu. Additionally, the asymmetric C–C coupling of *CHO+*CO, distributed between Cu and Pd sites, can lower the free energy change of rate-determining step to promote production of the C2+ products. Faradaic efficiency (FE) of the C2+ products over Cu2O-CuPd0.5μM was more than three times higher than that over untreated Cu2O NW, rising from 16.50 % to 54.47 % under −1 V (vs RHE) bias. Moreover, the FE for formate and CO decreased respectively from 28.57 % and 19.30 % to 3.69 % and 11.82 %, accompanied by a simultaneous increase in current density by 71.49 %.

Chemical Repair of Radical Damage to the GC Base Pair by DNA-Bound Bisbenzimidazoles.

The migration of an electron-loss center (hole) in calf thymus DNA to bisbenzimidazole ligands bound in the minor groove is followed by pulse radiolysis combined with time-resolved spectrophotometry. The initially observed absorption spectrum upon oxidation of DNA by the selenite radical is consistent with spin on cytosine (C), as the GC• pair neutral radical, followed by the spectra of oxidized ligands. The rate of oxidation of bound ligands increased with an increase in the ratio (r) ligands per base pair from 0.005 to 0.04. Both the rate of ligand oxidation and the estimated range of hole transfer (up to 30 DNA base pairs) decrease with the decrease in one-electron reduction potential between the GC• pair neutral radical of ca. 1.54 V and that of the ligand radicals (E0', 0.90-0.99 V). Linear plots of log of the rate of hole transfer versus r give a common intercept at r = 0 and a free energy change of 12.2 ± 0.3 kcal mol-1, ascribed to the GC• pair neutral radical undergoing a structural change, which is in competition to the observed hole transfer along DNA. The rate of hole transfer to the ligands at distance, R, from the GC• pair radical, k2, is described by the relationship k2 = k0 exp(constant/R), where k0 includes the rate constant for surmounting a small barrier.