The
electrochemical CO2 reduction reaction (CO2RR)
is a promising approach for converting fossil fuel emissions
into environmentally sustainable chemicals and fuels. The ability
to control the surface structure of CO2RR nanocatalysts
provides an opportunity to tune product selectivity. Bimetallic gold–copper
catalysts have been identified as emerging electrocatalyst candidates,
but Cu incorporation typically lowers product selectivity compared
with pure Au. Here we show sustained CO selectivity and activity up
to 49% Cu content in small (<2 nm), thiol-capped Au/Cu nanoparticles
(NPs). Bimetallic NPs containing 49% Cu selectivity converted CO2 into CO with 100 ± 6% CO Faradaic efficiency and average
mass activity of ∼500 mA/mg during a 12 h electrolysis experiment
at −0.8 V vs RHE. Au/Cu NPs synthesized without thiol ligands
selectively produced H2, whereas larger (>10 nm), thermally
dethiolated Au/Cu NPs produced a wider product distribution including
H2, CO, and C2H4. Density functional
theory (DFT) modeling of CO2RR and H2 evolution
at realistic, thiol-capped Au/Cu NP structures indicated that copper–thiol
surface structures sustained CO selectivity by stabilizing key *CO
intermediates while making *H binding less favorable. Calculations
also predicted that removing a significant fraction of the thiol ligands
would increase *CO binding strength such that desorption of CO product
molecules could become the most thermodynamically challenging step.
This result, coupled with increased *H stability on dethiolated nanoclusters,
points to decreased CO2RR selectivity for small, ligand-free
catalysts, which is in line with experimental observations from our
group and others. Our results demonstrate that thiol-ligand surface
structures can sustain the CO selectivity of bimetallic Au/Cu NPs
and reduce precious metal requirements for CO2RR.
The Adenomatoid Odontogenic Tumor presents in low frequency. It is originated from epithelial rests, specifically from the dental lamina, and shows similar characteristics to a wide variety of pathologies. Is a benign non-invasive lesion that can be manage by conservative treatment. Thus, is important to recognize and differentiate it from other pathologies that required more aggressive surgical treatment. The objective of the present article is to report a case of an Adenomatoid Odontogenic Tumor along with its common features.
The structural heterogeneity in mixed SWCNT samples results in extensive spectral complexity that can hamper a range of basic and applied research efforts. One approach to solving this problem is post-growth sorting, which unfortunately involves well known challenges. Here we report a photochemical strategy for spectral tailoring that uses monochromatic near-infrared (NIR) irradiation to selectively alter semiconducting (n,m) species based on their distinct and characteristic E11 optical transitions. This process does not physically isolate the targeted species, but it allows optical properties of the mixture to be modified without the need for physical separations. Our method achieves selective fluorescence quenching in aqueous dispersions of SWCNTs through irradiation of E11 transitions by NIR diode lasers in the presence of dissolved oxygen. Fluorescence emission from SWCNT species with transitions near the excitation wavelength is significantly and permanently suppressed, while the corresponding E11 absorptions are bleached and Raman D bands intensify. Results will be presented for several different oxygen headspace pressures and for wavelength-dependent irradiation data, which suggest a threshold consistent with the involvement of singlet O2. The method of near-IR photochemical tailoring may be useful for controlling SWCNT emission spectra in applications such as spectral bar-coding and strain sensing.
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