Recent Advances in Electrocatalytic Nitrogen Reduction to Produce Ammonia Under Ambient Conditions

Ammonia (NH3) is one of the most widely used chemicals in industry and agriculture, which is very important to the global economy. At present, the Haber Bosch process is adopted for ammonia synthesis in industry. The experimental temperature and pressure used in this process are relatively high, the process energy consumption is high, the one-way conversion of the hydrogen is low, and a large amount of carbon dioxide is discharged into the atmosphere, causing pollution to the environment. To solve its shortcomings, researchers began a new exploration. Electrocatalytic nitrogen reduction (NRR), as a clean and sustainable method of ammonia synthesis, has attracted extensive attention. However, the low activity and selectivity of electrocatalysts are one of the important challenges. Therefore, the search for cost-effective electrocatalysts has become one of the research hotspots of electrochemical ammonia synthesis. For enhancing the catalytic performance and selective performance of catalysts, scientists have carried out a lot of research on electrochemical nitrogen fixation catalysts. In this review article, electrolytic experimental devices, common ammonia detection research methods, and the electrocatalytic NRR mechanism are summarized, and then the research progress in electrocatalysts (precious metals, transition metals, and non-precious metals) is summarized. Then, the research progress of metal-based electrocatalysts is introduced, and the relevant theoretical calculations are given. The discussion of different catalytic systems provides ideas for the development and improvement of subsequent NRR electrocatalysts

Selection and Application of Quantitative Indicators of Paths Based on Graph Theory: A Case Study of Traditional Private and Antique Gardens in Beijing

Chinese Traditional Gardens (CTGs) are an important part of China’s cultural inheritance from the past. Today’s China has experienced rapid urbanization, raising the need for a new form of contemporary gardens intended to satisfy peoples’ need for traditional culture. Garden paths are important in CTGs; they are designed to show visitors changing views with each step, and to lead them to secluded, quiet places via winding paths. This enhances the ornamental interest of the gardens. Based on plane graphics, this study evaluates the characteristics of three types of garden paths in fourteen traditional gardens and a contemporary antique garden, the Daguan Garden in Beijing. The analysis uses correlation and factor analysis to integrate 28 quantitative path indicators into five aspects of average, scale, network, wide, and aggregation. The 28 indicators can be expressed by six simple indicators: average connection length, number of path sections, alpha index, average width, average tortuous angle, and concentration degree. The results show small variations of garden paths between traditional gardens, but a considerable difference between the contemporary garden and traditional gardens. The research proposes a framework for the quantification and comparison of garden path features that can be applied before and after garden path construction, for both ancient and modern garden styles. This framework generates garden path feature values and theoretical values of six indicators, and is not constrained by the garden scale. Therefore, it provides an accurate and efficient design tool for garden designers

Oxygen Vacancies Boosted by Laser Irradiation Enable NiCo Layered Double Hydroxide with a High Oxygen Reduction/Evolution Catalytic Activity in Zn–Air Batteries and Water Splitting

Layered double hydroxide (LDH) provides a unique platform to design low-cost multifunctional catalysts owing to the special lamellar structure and excellent performance. Herein, by using nickel-cobalt LDH grown on the conductive nickel foam (NF) skeleton (NiCo LDH/NF), a three-dimensional structure featured with multilayer petals is constructed. Benefiting from the simple and feasible fixed-point laser irradiation, NiCo LDH/NF shows boosted oxygen vacancies, resulting in efficient catalytic activities, with an oxygen evolution reaction overpotential of only 253.31 mV at 10 mA cm–2 and a half-wave potential of 0.79 V vs RHE for oxygen reduction reaction. Attractively, rechargeable Zn–air batteries (ZABs) using the laser-irradiated NiCo LDH/Ni foam (L-NiCo LDH/NF) as the catalytic electrode display a high peak power value of 126.29 mW cm–2, surpassing that of commercially grouped Pt/C-IrO2 (88.43 mW cm–2). Moreover, the as-obtained L-NiCo LDH/NF also delivers enhanced catalytic activity in hydrogen evolution. Accordingly, the developed ZABs can drive the overall water splitting reaction using L-NiCo LDH/NF as the electrodes. Meanwhile, the key role of oxygen vacancy in the catalyst was verified by using the calculation based on density functional theory. Therefore, the simple method of laser irradiation is confirmed as a feasible way to boost oxygen vacancies in materials with enabled multifunctional electrocatalysis

Self-Assembled Multiwalled Carbon Nanotube Films Assisted by Ureidopyrimidinone-Based Multiple Hydrogen Bonds

Self-assembled functionalized multiwalled carbon nanotube (MWNT) films were successfully constructed, linked by a kind of strong binding strength from the self-complementary hydrogen-bonding array of ureidopyrimidinone-based modules (UPM) attached. Employing the feasible reaction of isocyanate containing ureidopyrimidinone with amine modified MWNTs, the UPMs composed of ureidopyrimidinone and ureido were attached to MWNTs with the content as low as 0.6 mmol/g MWNTs. Upon multiple hydrogen-bonding interactions from incorporation of the AADD (A, hydrogen-bonding acceptor; D, hydrogen-bonding donor) quadruple hydrogen bonds of ureidopyrimidinone and the double hydrogen bonds of ureido group, UPM functionalized MWNTs (MWNT–UPM) can be well dispersed in the polar solvent of <i>N</i>,<i>N</i>-dimethylformamide (DMF), while they tend to self-assemble to give a self-supported film in the apolar solvent of CHCl₃. In addition, by using the multiple hydrogen-bonding interactions as the driving force, the layer-by-layer (LBL) MWNT–UPM films with high coverage on solid slides can be processed. Because of the self-association of MWNT–UPM in apolar solvent, it was found that the LBL assembly of MWNT–UPM was more favorable in the polar solvent of DMF than in the apolar solvent of CHCl₃. Moreover, the hydrogen-bonding linked MWNT–UPM films showed good stability upon soaking in different solvents. Furthermore, the as-prepared LBL films showed electrochemical active behaviors, exhibiting a remarkable catalytic effect on the reduction of nifedipine

A new polymorphism biomarker rs629367 associated with increased risk and poor survival of gastric cancer in chinese by up-regulated miRNA-let-7a expression.

BACKGROUND: Variant in pri-miRNA could affect miRNA expression and mature process or splicing efficiency, thus altering the hereditary susceptibility and prognosis of cancer. We aimed to assess miRNA-let-7 single nucleotide polymorphisms (SNP) associated with the risk and prognosis of gastric cancer (GC) as predicting biomarkers, and furthermore, its possible mechanisms. METHODS: A two-stage case-control study was designed to screen four miRNA SNPs (pri-let-7a-2 rs629367 and rs1143770, pri-let-7a-1 rs10739971, pri-let-7f-2 rs17276588) in 107 GC patients, 107 atrophic gastritis (AG), and matched 124 controls using PCR-RFLP. Two promising SNPs were validated in another independent 1949 samples (including 579 gastric cancer patients, 649 atrophic gastritis and 721 controls) using Sequenom MassARRAY platform and sequencing. RESULTS: We found that pri-let-7a-2 rs629367 CC variant genotype was associated with increased risks of gastric cancer and atrophic gastritis by 1.83-fold and 1.86-fold, respectively. For gastric cancer prognosis, patients with rs629367 CC genotype had significantly poorer survival than patients with AA genotype (log-rank P = 0.004). We further investigated the let-7a expression levels in serum and found that let-7a expression elevated gradually for rs629367 AA, CA, CC genotype in the atrophic gastritis group (P = 0.043). Furthermore, we confirmed these findings in vitro study by overexpressing let-7a carrying pri-let-7a-2 wild-type A or polymorphic-type C allele (P<0.001). CONCLUSIONS: pri-let-7a-2 rs629367 CC genotype could increase the risks of gastric cancer as well as atrophic gastritis and was also associated with poor survival of gastric cancer, which possibly by affecting the mature let-7a expression, and could serve as a predicting biomarker for high-risk and poor prognosis of gastric cancer

Enhanced Electronic Communication and Electrochemical Sensitivity Benefiting from the Cooperation of Quadruple Hydrogen Bonding and π–π Interactions in Graphene/Multi-Walled Carbon Nanotube Hybrids

By designing a molecule labeled as UPPY with both ureidopyrimidinone (UP) and pyrene (PY) units, the supramolecular self-assembly of multiwalled carbon nanotube (MWNT) and reduced graphene oxide (rGO) was driven by the UP quadruple hydrogen-bonding and PY-based π–π interactions to form a novel hybrid of rGO-UPPY-MWNT in which the morphology of rGO-wrapped MWNT was found. Bridged by the two kinds of noncovalent bonding, enhanced electronic communication occurred in rGO-UPPY-MWNT. Also, under the cooperation of UP quadruple hydrogen-bonding and PY-based π–π interactions, higher electrical conductivity and better charge transfer were observed for rGO-UPPY-MWNT, compared with the rGO-MWNT composite without such noncovalent bonds, and that with just single PY-based π–π interaction (rGO-PY-MWNT) or UP quadruple hydrogen bond (rGO-UP-MWNT). Specifically, the electrical conductivity of rGO-PY-MWNT hybrids was increased approximately sevenfold, and the interfacial charge transfer resistance was nearly decreased by 1 order of magnitude compared with rGO-MWNT, rGO-UP-MWNT, and rGO-PY-MWNT. Resulting from its excellent electrical conductivity and charge transfer properties, the rGO-UPPY-MWNT modified electrode exhibited enhanced electrochemical activity toward dopamine with detection limit as low as 20 nM