A Sweet Synthesis of MXenes.

Two-dimensional transition metal carbides/nitrides (MXenes) have shown great promise in various applications. However, mass production of MXenes suffers from the excessive use of toxic fluorine-containing reagents. Herein, a new method was validated for synthesizing MXenes from five MAX ceramics. The method features a minimized (stoichiometric) dosage of F-containing reagent (NaBF4) and polyols (glycerol, erythritol, and xylitol) as the reaction solvent. Due to the sweetness of polyols and the low environmental impact, we refer to this method as a "sweet" synthesis of MXenes. An in-depth molecular dynamics simulation study, combined with experimental kinetic parameters, further revealed that the diffusion of F- in the confined interplanar space is rate-determining for the etching reaction. The expansion of interlayer spacing by polyols effectively reduces the diffusion activation energy of F- and accelerates the etching reaction.

Explosive Leidenfrost-Droplet-Mediated Synthesis of Monodispersed High-Entropy-Alloy Nanoparticles for Electrocatalysis.

High-entropy-alloy nanoparticles (HEA NPs) exhibit promising potential in various catalytic applications, yet a robust synthesis strategy has been elusive. Here, we introduce a straightforward and universal method, involving the microexplosion of Leidenfrost droplets housing carbon black and metal salt precursors, to fabricate PtRhPdIrRu HEA NPs with a size of ∼2.3 nm. The accumulated pressure within the Leidenfrost droplet triggers an intense explosion within milliseconds, propelling the carbon support and metal salt rapidly into the hot solvent through explosive force. The exceptionally quick temperature rise ensures the coreduction of metal salts, and the dilute local concentration of metal ions limits the final size of the HEA NPs. Additionally, the explosion process can be fine-tuned by selecting different solvents, enabling the harvesting of diverse HEA NPs with superior electrocatalytic activity for alcohol electrooxidation and hydrogen electrocatalysis compared to commercial Pt (Pd) unitary catalysts.

Theoretical calculations and experimental verification of carbon dioxide reduction electrocatalyzed by metalloporphyrin.

Metal-functionalized porphyrin-like graphene structures are promising electrocatalysts for carbon dioxide reduction reaction (CO2RR) as their metal centers can modulate activity. Yet, the role of metal center of metalloporphyrins (MTPPs) in CO2 reaction activity is still lacking deep understanding. Here, CO2RR mechanism on MTPPs with five different metal centers (M = Fe, Co, Cu, Zn and Ni) are examined by first-principles calculations. The *COOH formation is the rate determined step on the five MTPP structures, and the CoTPP exhibits the best CO2RR activity while ZnTPP and NiTPP are the worst, which is also verified by our experiment. The CO2RR activity is controlled by adsorption states of intermediates (*CO, *COOH), i.e., chemisorption (e.g., on CoTPP) and physisorption (on ZnTPP and NiTPP) of intermediates will lead to good and poor activity, respectively. The deeper the d-band center of the porphyrin ring complexed metal atom, the weaker bonding of MTPP with CO and COOH. Theoretical calculations and experimental results indicate that MTPPs with Co and Fe centers lead to a reduction in the energy barriers for the two uphill reaction steps in the electrocatalytic CO2 reduction process, thereby enhancing CO2 reduction electrocatalytic activity. Faradaic efficiency of CO is correlated with the reaction energy barrier of the first proton-coupled electron reduction process, displaying a strong linear correlation. This work provides a fundamental understanding of MTPPs used as electrocatalysts for CO2RR.

Formation of Disordered High-Entropy-Alloy Nanoparticles for Highly Efficient Hydrogen Electrocatalysis.

Nanoparticles composed of high-entropy alloys (HEA NPs) exhibit remarkable performance in electrocatalytic processes such as hydrogen evolution and oxidations. In this study, two types of quinary HEA NPs of PtRhPdIrRu, are synthesized, featuring disordered and crystallized nanostructures, both with and without a boiling mixture. The disordered HEA NPs (d-HEA NPs) with a size of 3.5 nm is synthesized under intense boiling conditions, attributed to improved heat and mass transfer during reduction of precursors and particle growth. The disordered HEA NPs displayed an exceptionally high turnover frequency of 33.1 s-1 at an overpotential of 50 mV, surpassing commercial Pt NPs in acidic electrolytes by 5.4 times. Additionally, d-HEA NPs exhibited superior stability at a constant electrolyzing current of 50 mA cm-2 compared to commercial Pt NPs. When employed as the anodic catalyst in an H2-O2 fuel cell, d-HEA NPs demonstrated a remarkable high current power density of 15.3 kW per gram of noble metal. Consequently, these findings highlight the potential of d-HEA NPs in electrochemical applications involving hydrogen.

Catalyst Selection over an Electrochemical Reductive Coupling Reaction toward Direct Electrosynthesis of Oxime from NOx and Aldehyde.

Aqueous electrochemical coupling reactions, which enable the green synthesis of complex organic compounds, will be a crucial tool in synthetic chemistry. However, a lack of informed approaches for screening suitable catalysts is a major obstacle to its development. Here, we propose a pioneering electrochemical reductive coupling reaction toward direct electrosynthesis of oxime from NOx and aldehyde. Through integrating experimental and theoretical methods, we screen out the optimal catalyst, i.e., metal Fe catalyst, that facilitates the enrichment and C-N coupling of key reaction intermediates, all leading to high yields (e.g., ∼99% yield of benzaldoxime) for the direct electrosynthesis of oxime over Fe. With a divided flow reactor, we achieve a high benzaldoxime production of 22.8 g h-1 gcat-1 in ∼94% isolated yield. This work not only paves the way to the industrial mass production of oxime via electrosynthesis but also offers references for the catalyst selection of other electrochemical coupling reactions.

Alkali Metal Cation-Sulfate Anion Ion Pairs Promoted the Cleavage of C-C Bond During Ethanol Electrooxidation.

Direct ethanol fuel cells show great promise as a means of converting biomass ethanol derived from biomass into electricity. However, the efficiency of complete conversion is hindered by the low selectivity in breaking the C-C bond. This selectivity is determined by factors such as the material structure and reaction conditions, including the nature of the supporting electrolyte. Cations serve not only as facilitators of electricity conduction through ion migration but also as influencers of the reaction pathways. In this study, we utilized differential electrochemical mass spectrometry to track the in situ generation of CO2 during potential scanning. The presence of alkali cations led to an enhancement in the CO2 selectivity. In addition, in situ Raman spectroscopy provided evidence of the formation of alkali metal cation-sulfate anion ion pairs. The catalytic activity and CO2 selectivity were found to be directly correlated to the ionic strength of these ion pairs.

MOF Material-Derived Bimetallic Sulfide CoxNiyS for Electrocatalytic Oxidation of 5-Hydroxymethylfurfural.

The electrocatalytic conversion of biomass into high-value-added chemicals is one of the effective methods of green chemistry. Conventional metal catalysts have disadvantages, such as low atomic utilization and small surface areas. Catalyst materials derived from metal-organic frameworks (MOFs) have received much attention due to their unique physicochemical properties. Here, an MOF-derived non-precious metal CoxNiyS electrocatalyst was applied to the oxidation of biomass-derivative 5-hydroxymethylfurfural (HMF). The HMF oxidation reaction activities were modulated by regulating the content of Co and Ni bimetals, showing a volcano curve with an increasing proportion of Co. When the Co:Ni ratio was 2:1, the HMF conversion rate reached 84.5%, and the yield of the main product, 2,5-furandicarboxylic acid (FDCA), was 54%. The XPS results showed that the presence of high-valent nickel species after electrolysis, which further proved the existence and reactivity of NiOOH, as well as the synergistic effect of Co and Ni promoted the conversion of HMF. Increasing the content of Ni could increase the activity of HMF electrochemical oxidation, and increasing the content of Co could reduce the increase in the anodic current. This study has important significance for designing better HMF electrochemical catalysts in the future.

Elucidating the origin of catalytic activity of nitrogen-doped carbon coated nickel toward electrochemical reduction of CO2.

Converting CO2 into valuable chemicals and fuels through clean and renewable energy electricity provides a way to achieve sustainable development for human societies. In this study, carbon coated nickel catalysts (Ni@NCT) were prepared by solvothermal and high-temperature pyrolysis methods. A series of Ni@NC-X catalysts were obtained by pickling with different kinds of acids for electrochemical CO2 reduction reaction (ECRR). The results show that Ni@NC-N treated with nitric acid has the highest selectivity but lower activity, Ni@NC-S treated with sulfuric acid has the lowest selectivity, and Ni@NC-Cl treated with hydrochloric acid shows the best activity and good selectivity. At -1.16 V, Ni@NC-Cl has a considerable CO yield of 472.9 µmol h-1 cm-2, which is significantly superior to Ni@NC-N (327.5), Ni@NC-S (295.6) and Ni@NC (270.8). The controlled experiments show that there is a synergistic effect between Ni and N. The chlorine adsorbed on the surface can promote the performance of ECRR. The poisoning experiments indicate that the contribution of surface Ni atoms to the ECRR is very small, and the increase of activity is mainly due to the nitrogen doped carbon coated Ni particles. The relationship between activity and selectivity of ECRR on different acid-washed catalysts was correlated by theoretical calculations for the first time, which is also in good agreement with the experimental results.

Electric Field-Assisted Uptake of Hexavalent Chromium Ions with In Situ Regeneration of Carbon Monolith Adsorbents.

The uptake of hexavalent chromium (Cr(VI)) ions from wastewater is of great significance for environmental remediation and resource utilization. In this study, a self-designed instrument equipped with an oxidized mesoporous carbon monolith (o-MCM) as an electro-adsorbent is developed. o-MCM with a super hydrophilic surface displayed a high specific surface area (up to 686.5 m2  g-1 ). With the assistance of an electric field (0.5 V), the removal capacity of Cr(VI) ions is as high as 126.6 mg g-1 , much higher than that without an electric field (49.5 mg g-1 ). During this process, no reduction reaction of Cr(VI) to Cr(III) ions is observed. After adsorption, the reverse electrode with 10 V is used to efficiently desorb the ions on the carbon surface. Meanwhile, the in situ regeneration of carbon adsorbents can be obtained even after ten recycles. On this basis, the enrichment of Cr(VI) ions in a special solution is achieved with the assistance of an electric field. This work lays a foundation for the uptake of heavy metal ions from wastewater with the assistance of the electric field.

Configuration Sensitivity of Electrocatalytic Oxygen Reduction Reaction on Nitrogen-Doped Graphene.

As one of the most promising nonprecious metal catalysts for the oxygen reduction reaction (ORR), the structure of the active site on nitrogen-doped carbon materials is still under debate. Here, we report that the sensitivity of the ORR on the local configuration of multiple nitrogen dopants may be overlooked. Combining global structure searching with density functional theory calculations, we established the structure-activity relationship for 19 and 298 possible configurations of graphitic nitrogen-doped graphene with N content of 2 and 3%, respectively. It was revealed that the stability cannot be a screener to determine the major contributor to the activity. 77.5% of current density is contributed by the active configuration with 4.59% population on the graphene containing 3% nitrogen. It unambiguously demonstrates the configuration sensitivity of N-doped graphene for ORR and opens a new window to identifying the optimal structure of N-doped carbons for various applications.

Water coordinated on Cu(I)-based catalysts is the oxygen source in CO2 reduction to CO.

Catalytic reduction of CO2 over Cu-based catalysts can produce various carbon-based products such as the critical intermediate CO, yet significant challenges remain in shedding light on the underlying mechanisms. Here, we develop a modified triple-stage quadrupole mass spectrometer to monitor the reduction of CO2 to CO in the gas phase online. Our experimental observations reveal that the coordinated H2O on Cu(I)-based catalysts promotes CO2 adsorption and reduction to CO, and the resulting efficiencies are two orders of magnitude higher than those without H2O. Isotope-labeling studies render compelling evidence that the O atom in produced CO originates from the coordinated H2O on catalysts, rather than CO2 itself. Combining experimental observations and computational calculations with density functional theory, we propose a detailed reaction mechanism of CO2 reduction to CO over Cu(I)-based catalysts with coordinated H2O. This study offers an effective method to reveal the vital roles of H2O in promoting metal catalysts to CO2 reduction.

Mechanistic Insights into the Electrochemical Reduction of CO2 and N2 on the Regulation of a Boron Nitride Defect-Derived Two-Dimensional Catalyst using Density Functional Theory Calculations.

Electrochemical reductions of CO2 (ECRR) and N2 (ENRR) can not only reduce CO2 emissions in the air but also make use of N2 and H2O, the most extensive resources on earth, to produce high value-added chemicals, which has become one of the hot research directions. In this study, the formation energy (Ef) and dissolution potential (Udiss) of 96 two-dimensional catalysts derived from different defect sites of monoclinic crystal boron nitride (BN) were calculated, and the catalysts with thermodynamic and electrochemical stability were selected. The suitable catalysts for producing HCOOH (Ga/In@N-BN), CO (Sn@BN), and CH3OH (Co@N-BN) by ECRR and NH3 (Fe@BN) by ENRR were predicated based on a selective calculation method. The results obtained can provide guidance for the design and development of new catalysts for ECRR and ENRR.

Clinical and demographic features among patients with type 1 diabetes mellitus in Henan, China.

BACKGROUND: The hallmark of type 1 diabetes (T1D) is an absolute lack of insulin. However, many studies showed a tendency to heterogeneity in TID. We aimed to investigate the demographic and clinical characteristics in T1D and the differences in young-onset and adult-onset patients. METHODS: This retrospective study was conducted among 1943 patients with clinically diagnosed T1D. Medical records on patients' demographics, anthropometric measurements, and clinical manifestation were collected. According to the age at onset, the newly diagnosed patients were divided into the young-onset group (< 18 years, 234 patients, mean age 11 years) and adult-onset group (≥ 18 years, 219 patients, mean age 27 years). Pancreatic ß-cell function was assessed by fasting C-peptide (FCP) and 2-h C-peptide (2-h CP). RESULTS: The median age of patients at disease onset was 22 years. The median duration of patients was 3 years. The overall median glycated hemoglobin (HbA1c) value was 10.3 % [89(mmol/mol)]. The prevalence of diabetic retinopathy was 25.1 %. The overall rate of DKA at onset in the new-onset patients was 59.6 %. The frequency of overall dyslipidemia was 37.8 %. The most frequent dyslipidemia was low high-density lipoprotein-cholesterol (HDL) (29 %). The proportion of patients with anti-glutamic acid decarboxylase (GADA), insulin antibody (IAA) and islet cell antibody (ICA) were 28.1 %, 6.4 % and 21.6 %, respectively. The mean HbA1c showed a downward trend with age. Increasing or decreasing trends of overweight and obesity in this population during the period 2012 to 2018 was not found. Compared with young-onset T1D, adult-onset patients comprised better islet function (FCP: 0.4 vs. 0.3 ng/ml, P < 0.001; 2-h CP: 0.9 vs. 0.7 ng/ml P < 0.001, respectively) and glycemic control [12.9 % (117mmol/mol) vs. 11.7 % (104mmol/mol), P < 0.001], higher prevalence of diabetes condition in the male gender (64.4 % vs. 51.3 %, P = 0.006), higher proportion of obesity or overweight (24.6 % vs. 9.5 %, P = 0.002), higher frequency of GADA (33.7 % vs. 23.3 %, P = 0.025), and lower frequency of diabetic ketoacidosis at disease onset (64.5 % vs. 43.5 %, P < 0.001). CONCLUSIONS: This population was characterized by poor overall blood glucose control, high prevalence of DKA, dyslipidemia and diabetic retinopathy, and low prevalence of islet-related antibodies, and overweight or obesity. Adult-onset patients with T1D were not uncommon and had better clinical manifestations than young-onset patients. Any findings related to body mass index (BMI) and autoantibodies should be considered strictly exploratory due to excessive missing data.

Formation of Lattice-Dislocated Zinc Oxide via Anodic Corrosion for Electrocatalytic CO2 Reduction to Syngas with a Potential-Dependent CO:H2 Ratio.

The electrochemical reduction of CO2 and H2O to syngas, a widely used precursor for chemical synthesis, has attracted increased attention. However, producing syngas over a wide range of CO:H2 ratios is important for its potential application. Herein, a facile method using an anodic oxidizing zinc plate has been developed to obtain lattice-dislocated ZnO, which exhibited higher faradaic efficiencies (above 90%) of syngas than that of ZnO without lattice dislocation. Moreover, the ratio of CO to H2 can be regulated in a wide range from 0.28 to 2.11 by applying different electrolyzing potentials, which is applicable to the synthesis of various chemicals. With density functional theory calculations, we conclude that the lattice dislocation defects in ZnO promote the electroreduction of CO2. In addition, stability and electrochemical noise tests show that lattice-dislocated ZnO can withstand long-term operation due to its effective corrosion resistance.

Mechanistic Insights into Cyclic Voltammograms on Pt(111): Kinetics Simulations.

A detailed understanding of the electrochemistry of platinum electrodes is of great importance for the electrochemical oxidation of fuels and electrochemical reduction of dioxygen in fuel cells. The Pt(111) facet is the most representative model mimicking Pt nanoparticles and polycrystals for fundamental studies. Herein, we propose a site-specific model accompanied with the typical elementary steps of the electrochemistry of Pt(111) in non-adsorbing electrolyte within the potential range between 0.05 and 1.15 V versus reversible hydrogen electrode. Simulations were conducted at different scanning rates based on the kinetics models. We reproduce all the anodic and cathodic peaks observed in the reported experimental curves. These results demonstrate the underlying mechanisms of the peak formation in different potential regions.

Conversion of Ethanol via C-C Splitting on Noble Metal Surfaces in Room-Temperature Liquid-Phase.

Rh-catalyzed decomposition of ethanol into CO2 and CH4 via C-C bond splitting is reported in room-temperature liquid phase under atmospheric pressure. Mechanistic investigations show that C-C bond splitting of ethanol on the noble metal surface is rapid, and CO2 forms through the oxidation of α-CH xO and ß-CH x fragments after C-C bond splitting, while CH4 forms through the hydrogenation of ß-CH x utilizing H atoms from -OH, ß-CH x, and α-CH xOH fragments.

Platinum-tin oxide core-shell catalysts for efficient electro-oxidation of ethanol.

Platinum-tin (Pt/Sn) binary nanoparticles are active electrocatalysts for the ethanol oxidation reaction (EOR), but inactive for splitting the C-C bond of ethanol to CO2. Here we studied detailed structure properties of Pt/Sn catalysts for the EOR, especially CO2 generation in situ using a CO2 microelectrode. We found that composition and crystalline structure of the tin element played important roles in the CO2 generation: non-alloyed Pt46-(SnO2)54 core-shell particles demonstrated a strong capability for C-C bond breaking of ethanol than pure Pt and intermetallic Pt/Sn, showing 4.1 times higher CO2 peak partial pressure generated from EOR than commercial Pt/C.

Identification of amides derived from 1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid as potent inhibitors of human nicotinamide phosphoribosyltransferase (NAMPT).

Potent, 1H-pyrazolo[3,4-b]pyridine-containing inhibitors of the human nicotinamide phosphoribosyltransferase (NAMPT) enzyme were identified using structure-based design techniques. Many of these compounds exhibited nanomolar antiproliferation activities against human tumor lines in in vitro cell culture experiments, and a representative example (compound 26) demonstrated encouraging in vivo efficacy in a mouse xenograft tumor model derived from the A2780 cell line. This molecule also exhibited reduced rat retinal exposures relative to a previously studied imidazo-pyridine-containing NAMPT inhibitor. Somewhat surprisingly, compound 26 was only weakly active in vitro against mouse and monkey tumor cell lines even though it was a potent inhibitor of NAMPT enzymes derived from these species. The compound also exhibited only minimal effects on in vivo NAD levels in mice, and these changes were considerably less profound than those produced by an imidazo-pyridine-containing NAMPT inhibitor. The crystal structures of compound 26 and the corresponding PRPP-derived ribose adduct in complex with NAMPT were also obtained.

[Outflows of trihalomethane precursors from soils].

Outflows of trihalomethane formation potential (THMFPs) which was chosen as an index of the amount and reactivity with chlorine of THMs precursors from soils were studied with soil column experiment. The results indicated that factors influencing THMFP concentrations of leacheates were the physicochemical properties of soils, especially contents, composition and reactivities with chlorine of humic substances, the pH value of feed solution and cumulative leaching volume. The THMFP concentrations of leachates rose with increases in amounts of humic substances with high solubility as well as reactivity with chlorine. The effluents of soil samples contained the lowest THMFP concentrations under the feed solution of the lowest pH value (pH 3.0). THMFPs appeared to more easily flow out from soils with the feed solution of lower pH value, which was properly due to the increases in solubility of humic substances under the lower pH value conditions. In most cases, THMFP concentrations of leachates showed decline with the increase of cumulative leaching volumes of feed solution.