Defect
engineering is widely applied in transition metal dichalcogenides
(TMDs) to achieve electrical, optical, magnetic, and catalytic regulation.
Vacancies, regarded as a type of extremely delicate defect, are acknowledged
to be effective and flexible in general catalytic modulation. However,
the influence of vacancy states in addition to concentration on catalysis
still remains vague. Thus, via high throughput calculations, the optimized
sulfur vacancy (S-vacancy) state in terms of both concentration and
distribution is initially figured out among a series of MoS2 models for the hydrogen evolution reaction (HER). In order to realize
it, a facile and mild H2O2 chemical etching
strategy is implemented to introduce homogeneously distributed single
S-vacancies onto the MoS2 nanosheet surface. By systematic
tuning of the etching duration, etching temperature, and etching solution
concentration, comprehensive modulation of the S-vacancy state is
achieved. The optimal HER performance reaches a Tafel slope of 48
mV dec–1 and an overpotential of 131 mV at a current
density of 10 mA cm–2, indicating the superiority
of single S-vacancies over agglomerate S-vacancies. This is ascribed
to the more effective surface electronic structure engineering as
well as the boosted electrical transport properties. By bridging the
gap, to some extent, between precise design from theory and practical
modulation in experiments, the proposed strategy extends defect engineering
to a more sophisticated level to further unlock the potential of catalytic
performance enhancement.
Viral replication and microbial translocation from the gut to the blood during HIV infection lead to hyperimmune activation, which contributes to the decline in CD4+ T cell numbers during HIV infection. Programmed death-1 (PD-1) and interleukin-10 (IL-10) are both upregulated during HIV infection. Blocking interactions between PD-1 and programmed death ligand-1 (PD-L1) and between IL-10 and IL-10 receptor (IL-10R) results in viral clearance and improves T cell function in animal models of chronic viral infections. Here we show that high amounts of microbial products and inflammatory cytokines in the plasma of HIV-infected subjects lead to upregulation of PD-1 expression on monocytes that correlates with high plasma concentrations of IL-10. Triggering of PD-1 expressed on monocytes by PD-L1 expressed on various cell types induced IL-10 production and led to reversible CD4+ T cell dysfunction. We describe a new function for PD-1 whereby microbial products inhibit T cell expansion and function by upregulating PD-1 levels and IL-10 production by monocytes after binding of PD-1 by PD-L1.
A new azine-linked covalent organic framework, ACOF-1, was synthesized by condensation of hydrazine hydrate and 1,3,5-triformylbenzene under solvothermal conditions. ACOF-1 has a high surface area and a small pore size, and it can store up to 177 mg g(-1) of CO2, 9.9 mg g(-1) of H2, and 11.5 mg g(-1) of CH4, at 273 K and 1 bar, with high selectivity towards CO2 over N2 and CH4.
A real optimal Fe content: For N and Fe co-doped carbon electrocatalysts for oxygen reduction reactions (ORRs) it is found that there is a real optimal trace Fe content (Peak II), which has never been observed before. The real optimal electrocatalyst shows superior high activity for ORR and possesses the best price/performance ratio ever.
For
the goal of practical industrial development of fuel cells,
inexpensive, sustainable, and high performance electrocatalysts for
oxygen reduction reactions (ORR) are highly desirable alternatives
to platinum (Pt) and other rare materials. In this work, sustainable
fluorine (F)-doped carbon blacks (CB-F) as metal-free, low-cost, and
high-performance electrocatalysts for ORR were synthesized for the
first time. The performance (electrocatalytic activity, long-term
operation stability, and tolerance to poisons) of the best one (BP-18F,
based on Black Pearls 2000 (BP)) is on the same level as Pt-based
or other best non-Pt-based catalysts in alkaline medium. The maximum
power density of alkaline direct methanol fuel cell with BP-18F as
the cathode (3 mg/cm2) is ∼15.56 mW/cm2 at 60 °C, compared with a maximum of 9.44 mW/cm2 for commercial Pt/C (3 mgPt/cm2). All these
results unambiguously demonstrate that these sustainable CB-F catalysts
are the most promising alternatives to Pt in an alkaline fuel cell.
Since sustainable carbon blacks are 10 000 times less expensive
and much more abundant than Pt or other rare materials, these CB-F
electrocatalysts possess the best price/performance ratio for ORR
to date.
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