Defect electrocatalytic mechanism: concept, topological structure and perspective

Carbon-based materials have been attracting intense interest for electrocatalysis due to their various merits, such as abundance, low cost, high conductivity and tunable molecular structures. However, to date, the electrochemical activities of these electrocatalysts are mainly attributed to different active dopants (e.g. N, B, P or S), leading to a common concept that heteroatom doping is essential for carbon-based electrocatalysts. Recently, we presented a new concept where the specific topological defects could activate the oxygen reduction reaction (ORR) and developed a facile method to create such unique defects. Subsequent research has extended this new mechanism to other reactions, such as the hydrogen and oxygen evolution reactions (HER and OER) and confirmed that heteroatom doping is not essential but that these defects can serve as actives sites for electrochemical reactions. This new theory then creates a new research direction in electrocatalysis. In this short review, we summarise the origin and presentation of the defect mechanism concept, the possible topological defect structures that are effective for electrochemical reactions, the formation of desirable defects, the challenges in the synthesis and characterization of typical defects and future research directions on the electrochemical defect mechanism

Catalytically enhanced hydrogen sorption in Mg-MgH2 by coupling vanadium-based catalyst and carbon nanotubes

Mg (MgH2)-based composites, using carbon nanotubes (CNTs) and pre-synthesized vanadium-based complex (VCat) as the catalysts, were prepared by high-energy ball milling technique. The synergistic effect of coupling CNTs and VCat in MgH2 was observed for an ultra-fast absorption rate of 6.50 wt. % of hydrogen per minute and 6.50 wt. % of hydrogen release in 10 min at 200 °C and 300 °C, respectively. The temperature programmed desorption (TPD) results reveal that coupling VCat and CNTs reduces both peak and onset temperatures by more than 60 °C and 114 °C, respectively. In addition, the presence of both VCat and CNTs reduces the enthalpy and entropy of desorption of about 7 kJ/mol H2 and 11 J/mol H2·K, respectively, as compared to those of the commercial MgH2, which ascribe to the decrease of desorption temperature. From the study of the effect of CNTs milling time, it is shown that partially destroyed CNTs (shorter milling time) are better to enhance the hydrogen sorption performance

Fluorination-induced magnetism in boron nitride nanotubes from ab initio calculations

Ab initio calculations were conducted to investigate the electronic structures and magnetic properties of fluorinated boron nitride nanotube (F-BNNT). It was found that the chemisorption of F atoms on the B atoms of BNNT can induce spontaneous magnetization, whereas no magnetism can be produced when the B and N atoms are equally fluorinated. This provides a different approach to tune the magnetic properties of BNNTs as well as a synthetic route toward metal-free magnetic materials.<br /

Scalable and controllable synthesis of atomic metal electrocatalysts assisted by an egg-box in alginate

Herein, a general strategy is developed to synthesize atomic metal catalysts using sustainable and earth-abundant sodium alginate (Na-Alg), a common seaweed extract, as a precursor. The “egg-box” structure in Na-Alg after ion-exchange with metal cations (Zn2+, Co2+, Ni2+, Cu2+, etc.) is the key to achieve a scalable and controllable synthesis of highly dispersed atomic metals. For instance, atomic Co, Ni and Cu have been successfully synthesized using this method. As a representative, the as-synthesized atomically dispersed Co on reduced graphene oxide (A-Co/r-GO) can reach a maximum metal loading of 3.6 wt%, showing outstanding catalytic activity and stability for the oxygen reduction reaction (ORR) with a half-wave potential (E1/2) of 0.842 V vs. RHE that is more positive than that of 20 wt% Pt/C (0.827 V vs. RHE) in alkaline solutions. The A-Co/r-GO catalyzed zinc-air batteries (ZABs) outperform Pt/C-based ZABs in the aspects of discharge voltage and specific zinc capacity, and can work robustly for more than 250 h with negligible voltage loss with refueling the Zn anode and KOH electrolyte periodically. This work opens up a new strategy for a general, practical and scalable synthesis of atomic metal catalysts at very low cost.No Full Tex

Boosting oxygen reduction and hydrogen evolution at the edge sites of a web-like carbon nanotube-graphene hybrid

Identifying catalytically active sites in graphene-based catalysts is critical to improved oxygen reduction reaction (ORR) electrocatalysts for fuel-cell applications. To generate abundant active edge sites on graphene-based electrocatalysts for superior electrocatalytic activity, rather than at their basal plane, has been a challenge. A new type of ORR electrocatalyst produced using fluidization process and based on a three-dimensional hybrid consisting of horizontally-aligned carbon nanotube and graphene (CNT-G), featured abundant active edge sites and a large specific surface area (863\ua0m\ua0g). The Pt-doped CNT-G exhibited an increase of about 55% in mass activity over the state-of-the-art commercial Pt/C and about 164% over Pt/N-graphene in acidic medium, and approximately 54% increase in kinetic limiting current than the Pt/C at low overpotential in alkaline medium. The higher mass activity indicates that less Pt is required for the same performance, reducing the cost of fuel cell electrocatalyst. In hydrogen evolution reaction (HER), both the metal-free CNT-G and Pt/CNT-G exhibited superior electrocatalytic activity compared to N-doped graphene and commercial Pt/C, respectively

Perioperative dynamic alterations in peripheral regulatory T and B cells in patients with hepatocellular carcinoma

<p>Abstract</p> <p>Background</p> <p>Intratumoral and circulating regulatory T cells (Tregs) have been shown to be critical in the pathogenesis of hepatocellular carcinoma (HCC). However there is limited knowledge on the alterations of regulatory B cells (Bregs). We here investigated perioperative dynamic alterations of peripheral circulating Tregs and Bregs in HCC patients to reveal the relationship between regulatory lymphocytes and its clinical implications.</p> <p>Methods</p> <p>36 patients with HCC, 6 with chronic hepatitis B infection and 10 healthy donors were enrolled for this study. Frequencies of peripheral Tregs and Bregs were measured by flow cytometry with antibodies against CD4, CD25, CD127, CD19 and IL-10 before, and after radical surgery. Then, clinical informatics of HCC patients was achieved through Digital Evaluation Score System (DESS) for the assessment of disease severity. Finally, we analysed correlations between digitalized clinical features and kinetics of circulating regulatory lymphocytes.</p> <p>Results</p> <p>Level of circulating CD4⁺CD25⁺CD127^-Tregs in HCC patients was significantly lower than that in healthy donors and patients with chronic hepatitis B infection before surgery, but was increased after surgery. Preoperative level of CD19⁺IL-10⁺Bregs in HCC patients was also significantly lower than the other groups. However it dramatically was elevated right after surgery and remained elevated compared to controls (about 7 days after surgery, <it>P </it>= 0.04). Frequency of circulating Tregs was correlated with circulating leukocytes, ferritin, and clinical features suggesting tumor aggressiveness including portal vein thrombosis, hepatic vein involvement and advanced clinical stages. Frequency of circulating Bregs was associated with Hepatitis B e Antigen (HBeAg) and Hepatitis B virus (HBV) DNA copy number. In addition, DESS was significantly and positively correlated with other staging systems.</p> <p>Conclusion</p> <p>Frequencies of peripheral Tregs and Bregs in HCC patients increased after surgery. These results suggest that a postoperative combination of therapies against Tregs and Bregs may be beneficial for better outcome of HCC patients after resection.</p

The Proinflammatory Cytokines IL-18, IL-21, and IFN-γ Differentially Regulate Liver Inflammation and Anti-Mitochondrial Antibody Level in a Murine Model of Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is a cholestatic liver disease primarily featured by autoimmune-mediated damage of intrahepatic small- and medium-sized bile ducts. Elevated serum proinflammatory cytokines, serum anti-mitochondrial antibodies (AMAs), liver inflammation, and fibrosis are also hallmarks of PBC disease. However, whether the elevated proinflammatory cytokines play a role in autoimmune cholangitis remains unknown. Herein, we utilized the p40-/-IL-2Rα-/- PBC mouse model to investigate the roles of proinflammatory cytokines IL-18, IL-21, and IFN-γ in the onset and progression of PBC. IL-18-/-, IFN-γ-/-, and IL-21-/- mice were crossed with p40-/-IL-2Ra+/- mice, respectively, to produce corresponding cytokine-deficient PBC models. Autoantibody level, liver inflammation, and bile duct injury were analyzed. We found that livers from p40-/-IL-2Rα-/- mice exhibit similar transcriptomic characters of PBC patients. In p40-/-IL-2Rα-/- mice, deletion of IL-18 has no remarkable effect on disease progression, while deletion of IL-21 indicates that it is necessary for AMA production but independent of liver inflammation and cholangitis. IFN-γ is responsible for both AMA production and liver inflammation in our model. Our results demonstrate that different proinflammatory cytokines can regulate different effector functions in PBC pathogenesis and need to be considered in PBC treatment

Combined transcriptome and widely targeted metabolome analysis reveals the potential mechanism of HupA biosynthesis and antioxidant activity in Huperzia serrata

IntroductionHuperzia serrata is a traditional Chinese herb that has gained much attention for its production of Huperzine A (HupA). HupA has shown promise on treating Alzheimer's disease (AD). However, the biosynthetic pathway and molecular mechanism of HupA in H. serrata are still not well understood.MethodsIntegrated transcriptome and metabolome analysis was performed to reveal the molecular mechanisms related to HupA biosynthesis and antioxidant activity in Huperzia serrata.ResultsHT (in vitro H. serrata thallus) exhibits higher antioxidant activity and lower cytotoxicity than WH (wild H. serrata). Through hierarchical clustering analysis and qRT-PCR verification, 7 important enzyme genes and 13 transcription factors (TFs) related to HupA biosynthesis were detected. Among them, the average |log2FC| value of CYP (Cytochrome P450) and CAO (Copper amine oxidase) was the largest. Metabolomic analysis identified 12 metabolites involved in the HupA biosynthesis and 29 metabolites related to antioxidant activity. KEGG co-enrichment analysis revealed that tropane, piperidine and pyridine alkaloid biosynthesis were involved in the HupA biosynthesis pathway. Furthermore, the phenylpropanoid, phenylalanine, and flavonoid biosynthesis pathway were found to regulate the antioxidant activity of H. serrata. The study also identified seven important genes related to the regulation of antioxidant activity, including PrAO (primary-amine oxidase). Based on the above joint analysis, the biosynthetic pathway of HupA and potential mechanisms of antioxidant in H. serrata was constructed.DiscussionThrough differential transcriptome and metabolome analysis, DEGs and DAMs involved in HupA biosynthesis and antioxidant-related were identified, and the potential metabolic pathway related to HupA biosynthesis and antioxidant in Huperzia serrata were constructed. This study would provide valuable insights into the HupA biosynthesis mechanism and the H. serrata thallus medicinal value

Switched photocurrent on tin sulfide-based nanoplate photoelectrodes

A new type of SnS2 nanoplate photoelectrode is prepared by using a mild wet-chemical method. Depending on the calcination temperatures, SnS2-based photoelectrodes can either retain their n-type nature with greatly enhanced anodic photocurrent density (ca. 1.2 mA cm(-2) at 0.8V vs. Ag/AgCl) or be completely converted into p-type SnS to generate approximately 0.26 mA cm(-2) cathodic photocurrent density at -0.8 V vs. Ag/AgCl. The dominance of sulfur and tin vacancies are found to account for the dramatically different photoelectrochemical behaviors of n-type SnS2 and p-type SnS photoelectrodes. In addition, the band structures of n-type SnS2 and p-type SnS photoelectrodes are also deduced, which may provide an effective strategy for developing SnS2/SnS films with controllable energy-band levels through a simple calcination treatment

Pressure Fluctuation Characteristics of High-Pressure Common Rail Fuel Injection System

In high-pressure common rail fuel injection system, fuel pressure wave propagates back and forth in the system during fuel injection, and the cycle fuel injection volume is affected by the fluctuation of fuel injection pressure. Therefore, to reduce the influence of pressure fluctuation on the cycle fuel injection volume fluctuation, it is of great theoretical significance to analyze the mechanism of pressure fluctuation and its influence law. In this chapter, the dynamic pressure fluctuation characteristics of the high-pressure common rail fuel injection system are analyzed based on the injector inlet pressure, and experimental research and theoretical analysis are carried out for the time domain and frequency domain characteristics of injector inlet pressure fluctuation, aiming at revealing the pressure fluctuation mechanism and its influence law, and providing theoretical support for improving the control accuracy of multiple injection cycle fuel injection volume