Stabilizing perovskite precursors with the reductive natural amino acid for printable mesoscopic perovskite solar cells

Solution processability significantly advances the development of highly-efficient perovskite solar cells.However,the precursor solution tends to undergo irreversible degradation reactions,impairing the device performance and reproducibility.Here,we utilize a reductive natural amino acid,Nacetylcysteine(NALC),to stabilize the precursor solution for printable carbon-based hole-conductorfree mesoscopic perovskite solar cells.We find that I_(2) can be generated in the aged solution containing methylammonium iodide(MI) in an inert atmosphere and speed up the MA-FA^(+)(formamidinium) reaction which produces large-size cations and hinders the formation of perovskite phase.NALC effectively stabilizes the precursor via its sulfhydryl group which reduces I_(2) back to I^(-)and provides H^(+).The NALC-stabilized precursor which is aged for 1440 h leads to devices with a power conversion efficiency equivalent to 98% of that for devices prepared with the fresh precursor.Furthermore,NALC improves the device power conversion efficiency from 16.16% to 18.41% along with enhanced stability under atmospheric conditions by modifying grain boundaries in perovskite films and reducing associated defects.

Chemoselective Reduction of Fenofibric Acid to Alcohol in the Presence of Ketone by Mixed Anhydride and Sodium Borohydride

A highly efficient and facile protocol for the selective reduction of carboxylic acid of Fenofibric acid to corresponding alcohol was developed. The selective reduction was carried out by activation of carboxylic acid by mixed anhydride followed by the reaction of sodium borohydride in presence of methanol. This is the first example of chemoselective reduction of carboxylic acid to alcohol in presence of a ketone without any external catalyst or ligand in a single step. The reaction offers wide applicability for the selective carboxylic group reduction methodology. The chemoselective reduction was demonstrated by the reduction of Fenofibric acid, an active metabolite of the drug Fenofibrate, to corresponding alcohol in excellent selectivity, yield, and purity.

NaBH4-induced phase transition of CoSe_(2) with abundant Se deficiency for acidic oxygen reduction to hydrogen peroxide

Electrocatalytic oxygen reduction(ORR)via the 2e−pathway to form H_(2)O_(2) in acidic medium has attracted extensive attention.However,the low activity,insufficient selectivity and high cost of catalysts have been the bottlenecks.Herein,CoSe_(2) with abundant Se deficiency was synthesized by a simple hydrothermal method,and the addition of NaBH4-induced CoSe_(2) phase transition from orthorhombic to cubic phase with more Se deficiency.The cubic phase CoSe_(2) with abundant Se deficiency can effectively regulate the surface electronic structure with suitable binding energies of*OOH and*O,which shows high activity,selectivity and long-term stability for acidic ORR to H_(2)O_(2).The onset potential is as low as 0.73 V vs.reversible hydrogen electrode(RHE),the H_(2)O_(2) selectivity is 84%(0 V vs.RHE),and the average electron transfer number is about 2.3.Furthermore,the H_(2)O_(2) yield measured using a flow cell is as high as 115.92 mmol·gcat.^(−1)·h^(−1) and the Faradaic efficiency is 70%at 0 V vs.RHE,which presents high potential in electrocatalytic acidic ORR to H_(2)O_(2) and organic pollutant degradation using the electron-Fenton process.

Key genes expression of reductive tricarboxylic acid cycle from deep-sea hydrothermal chemolithoautotrophic Caminibacter profundus in response to salinity, pH and O_2

CO2 fixation pathway of Caminibacter profundus, a chemolithoautotrophic e-Proteobacteria from deep-sea hydrothermal vent, was determined and characterized by genetic and enzymatic analyses. Gene expression of key enzymes for CO2 fixation in response to salinity, pH and O2 in Medium 829 were also investigated. The results demonstrate that C. profundus contained aclB, porA and oorA, the genes encoding key enzymes of reductive tricarboxylic acid （rTCA） cycle. However, genes fragments of cbbL and cbbMencoding key enzyme of Calvin cycle were not recovered. Key enzymatic activities of ATP citrate lyase （ACL）, pyruvate： ferredoxin oxidoreductase （POR） and 2-oxoglutarate： ferredoxin oxidoreductase （OOR） were also present in C. profun- dus. The combination of genetic and enzymatic analyses confirm that C. profundus adopted rTCA cycle for carbon assimilation. The results of aclB and oorA relative expressions of C. profundus demonstrate that the ranges of environmental factors for high genes expression were sea salt 3.0%-5.0% （optimum 3.0%）, pH 5.0-6.5（optimum pH 6.5）, anaerobic to microaerobic conditions （optimum 1.0% 02）. Gene expression pat- terns under different conditions show similar patterns with bacterial growth, revealing that key rTCA cycle genes provided molecular basis for bacterial growth and propagation. Our results suggest that C. profun- dus could regulate key genes of rTCA cycle for carbon assimilation and energy metabolism in response to environmental fluctuations in hydrothermal vent.

A NEW ONE-STEP REDUCTIVE N-ALKYLATION OF AMINO ACIDS AND THEIR ESTERS

The reductive alkylation of amine with carbonyl compounds using sodium hydrogen telluride has been investigated in recent years. Application of this method to the synthesis of N-alkyl derivatives of biologically important amino acids and their esters is described.

Cr(Ⅵ) reduction capability of humic acid extracted from the organic component of municipal solid waste

The capacity of humic acid extracted from organic waste （HAw） to reduce Cr（Ⅵ） was tested at pH 2.5,4 and 6 and compared with coal-derived humic acid （HAc）.HAw was more effective than HAc in reducing Cr（Ⅵ）.The kinetics of Cr（Ⅵ） reductions depended strongly on pH.The calculation of the apparent rate coefficients indicated that HAw was more efficient at reducing Cr（Ⅵ） than HAc,but was also more efficient than HAs from soil and peat.The reduction capability of HAs depends on the type of functional groups （i.e.,thiols and phenols） present,rather than the free radicals.HAw was more efficient at reducing Cr（Ⅵ） than HAc because more reactive phenols were present,i.e.,methoxy-and methyl-phenols.

Optimizing the crystallinity and acidity of H-SAPO-34 by fluoride for synthesizing Cu/SAPO-34 NH_3-SCR catalyst

A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media.The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,N_2 physisorption,temperature-programmed desorption of NH_3（NH_3-TPD） and nuclear magnetic resonance（NMR） measurements.The results showed that a certain concentration of F- anions promoted the nucleation and crystallization of H-SAPO-34.The H-SAPO-34 synthesized in the fluoride media showed high crystallinity,uniform particle size distribution,large specific surface area and pore volume,and enhanced acidity.Therefore,Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH_3（NH_3-SCR） reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species.

Formic acid as an alternative reducing agent for the catalytic nitrate reduction in aqueous media

Formic acid was used for the nitrate reduction as a reductant in the presence of Pd：Cu/γ-alumina catalysts. The surface characteristics of the bimetallic catalyst synthesized by wet impregnation were investigated by SEM, TEM-EDS. The metals were not distributed homogeneously on the surface of catalyst, although the total contents of both metals in particles agreed well with the theoretical values. Formic acid decomposition on the catalyst surface, its influence on solution pH and nitrate removal efficacy was investigated. The best removal of nitrate （50 ppm） was obtained under the condition of 0.75 g/L catalyst with Pd：Cu ratio （4：1） and two fold excess of formic acid. Formic acid decay patterns resembled those of nitrate removal, showing a linear relationship between kf （formic acid decay） and k （nitrate removal）. Negligible amount of ammonia was detected, and no nitrite was detected, possibly due to buffering effect of bicarbonate that is in situ produced by the decomposition of formic acid, and due to the sustained release of H2 gas.

Preparation and Electrochemical Performance of Nano-Co_3O_4 Anode Materials from Spent Li-Ion Batteries for Lithium-Ion Batteries

A hydrometallurgical process for the recovery of cobalt oxalate from spent lithium-ion batteries was used to recycle cobalt compound by using alkali leaching, reductive acid leaching and chemical deposition of cobalt oxalate. The recycled cobalt oxalate was used to synthesize nano-Co3O4 anode material by sol-gel method. The samples were characterized by thermal gravity analysis and differential thermal analysis （TGA/DTA）, X-ray diffraction （XRD）, scanning electron microscopy （SEM） and charge/discharge measurements. The influence of molar ratio of Co2＋ to citric acid and calcination temperature on the structure and electrochemical performance of nano-Co3O4 was evaluated. As the molar ratio of Co2＋ to citric acid is 1：1, the face-centered cubic （fcc） Co3O4 powder shows the discharge capacity of 760.9 mA h g-1, the high coulombic efficiency of 99.7% in the first cycle at the current density of 125 mA g-l, and the excellent cycling performance with the reversible capacity of 442.3 mA h g-1 after 20 cycles at the current density of 250 mA g-1.

Influence of phase and microstructure on the rate of hydrochloric acid leaching in pretreated Panzhihua ilmenite

The present study investigated the influence of high temperature oxidation and reduction pretreatments on the leaching rate ofPanzhihua ilmenite. The as-pretreated ilmenite was leached with 20% HCI at 105 ℃, The leaching process was controlled by the phases and microstructures that evolved during the pretreatment processes. The leaching kinetics of pure hematite, ilmenite and pseudobrookite were characterized to clarify the phase effect on the iron-leaching rate; the rate of iron leaching occurs in the following order in the HCI solution： hematite （ferric iron） 〉 ilmenite （ferrous iron） 〉〉 pseudobrookite （ferric iron）. Therefore, the often-cited notion that ferrous iron dissolves faster in HCl solutions than ferric iron when explaining the pretreatment effects is inaccurate. Moreover, the oxidation pretreatment （at 600-1000 ℃ for 4 h） cannot destroy the dense structure of the Panzhihua ilmenite. Therefore, the influence exerted by the oxidation on the leaching process is primarily determined by the phase change; oxidation at 600 and 700℃ slightly increased the rate of iron leaching because the ilmenite was transformed into hematite, while the oxidation at 900-1000℃ significantly reduced the rate of iron leaching because a pseudobrookite phase formed. The reduction effect was subsequently investigated; the as-oxidized ilmenite was reduced under H2 at 750 ℃ for 30 min. The reduction significantly accelerated the rate of subsequent iron leaching such that nearly all of the iron had dissolved after leaching for 2 h in 20% HCl at 105 ℃. This enhanced iron-leaching rate is mainly attributed to the cracks and holes that formed during the reduction process.

Detailed profiling of carbon fixation of in silico synthetic autotrophy with reductive tricarboxylic acid cycle and Calvin-Benson-Bassham cycle in Esherichia coli using hydrogen as an energy source

Carbon fixation is the main route of inorganic carbon in the form of CO2 into the biosphere.In nature,RuBisCO is the most abundant protein that photosynthetic organisms use to fix CO2 from the atmosphere through the Calvin-Benson-Bassham(CBB)cycle.However,the CBB cycle is limited by its low catalytic rate and low energy efficiency.In this work,we attempt to integrate the reductive tricarboxylic acid and CBB cycles in silico to further improve carbon fixation capacity.Key heterologous enzymes,mostly carboxylating enzymes,are inserted into the Esherichia coli core metabolic network to assimilate CO2 into biomass using hydrogen as energy source.Overall,such a strain shows enhanced growth yield with simultaneous running of dual carbon fixation cycles.Our key results include the following.(i)We identified two main growth states:carbon-limited and hydrogenlimited;(ii)we identified a hierarchy of carbon fixation usage when hydrogen supply is limited;and(iii)we identified the alternative sub-optimal growth mode while performing genetic perturbation.The results and modeling approach can guide bioengineering projects toward optimal production using such a strain as a microbial cell factory.

Roles of Thioredoxins in the Obligate Anaerobic Green Sulfur Photosynthetic Bacterium Chlorobaculum tepidum

Thioredoxin is a small ubiquitous protein that is involved in the dithiol-disulfide exchange reaction, byway of two cysteine residues located on the molecule surface. In order to elucidate the role of thioredoxin in Chlorobaculum tepidurn, an anaerobic green sulfur bacterium that uses various inorganic sulfur compounds and H2S as electron donors under strict anaerobic conditions for growth, we applied the thioredoxin affinity chromatography method （Motohashi et al., 2001）. In this study, 37 cytoplasmic proteins were captured as thioredoxin target candidates, including proteins involved in sulfur assimilation. Furthermore, six of the candidate proteins were members of the reductive tricarboxylic acid cycle （pyruvate orthophosphate dikinase, pyruvate flavodoxin/ferredoxin oxidoreductase, ^-oxoglutarate synthase, citrate lyase, citrate synthase, malate dehydrogenase）. The redox sensitivity of three enzymes was then examined： citrate lyase, citrate synthase, and malate dehydrogenase, using their recombinant proteins. Based on the information relating to the target proteins, the significance of thioredoxin as a reductant for the metabolic pathway in the anaerobic photosynthetic bacteria is discussed.

Efficient Synthesis of a-Amino Acid Derivatives via Phase-transfer-catalyzed Directed Reductive Amination

An efficient phase-transfer-catalyzed directed reductive amination of α-keto esters was described using simple substituted benzyl amines as nitrogen source and K2CO3 as base at room temperature, giving a series of aliphatic a-amino acid derivatives in moderate to high yields（up to 99%）. Preliminary study on this asymmetric process showed that cinchona-derived phase transfer catalyst was elTective, aflbrding the corresponding product in 13% e.e. and 40% yield.