Single atom catalysts (SACs) with the maximized metal atom efficiency have sparked great attention. However, it is challenging to obtain SACs with high metal loading, high catalytic activity, and good stability. Herein, we demonstrate a new strategy to develop a highly active and stable Ag single atom in carbon nitride (Ag‐N2C2/CN) catalyst with a unique coordination. The Ag atomic dispersion and Ag‐N2C2 configuration have been identified by aberration‐correction high‐angle‐annular‐dark‐field scanning transmission electron microscopy (AC‐HAADF‐STEM) and extended X‐ray absorption. Experiments and DFT calculations further verify that Ag‐N2C2 can reduce the H2 evolution barrier, expand the light absorption range, and improve the charge transfer of CN. As a result, the Ag‐N2C2/CN catalyst exhibits much better H2 evolution activity than the N‐coordinated Ag single atom in CN (Ag‐N4/CN), and is even superior to the Pt nanoparticle‐loaded CN (PtNP/CN). This work provides a new idea for the design and synthesis of SACs with novel configurations and excellent catalytic activity and durability.
Zeolite-confined metal nanoparticles (NPs) have attracted much attention owing to their superior sintering resistance and broad applications for thermal and environmental catalytic reactions. However, the pore size of the conventional zeolites is usually below 2 nm, and reactants are easily blocked to access the active sites. Herein, a facile in situ mesoporogen-free strategy is developed to design and synthesize palladium (Pd) NPs enveloped in a single-crystalline zeolite (silicalite-1, S-1) with intra-mesopores (termed Pd@IM-S-1). Pd@IM-S-1 exhibited remarkable light alkanes deep oxidation performances, and it should be attributed to the confinement and guarding effect of the zeolite shell and the improvement in mass-transfer efficiency and active metal sites accessibility. The Pd−PdO interfaces as a new active site can provide active oxygen species to the first C−H cleavage of light alkanes. This work exemplifies a promising strategy to design other high-performance intra-crystalline mesoporous zeolite-confined metal/metal oxide catalysts for high-temperature industrial thermal catalysis.
Atmospheric proteinaceous matter
is characterized by ubiquity and
potential bioavailability. However, little is known about the origins,
secondary production processes, and biogeochemical role of proteinaceous
matter in wet deposition. Precipitation samples were collected in
suburban Guiyang (southwestern China) over a 1 year period to investigate
their chemical components, mainly including dissolved combined amino
acids (DCAAs), dissolved free AAs (DFAAs), and nonleachable particulate
AAs (PAAs). Glycine was most abundant in the DFAAs, while the dominant
species in DCAAs and PAAs was glutamic acid (including deaminated
glutamine). The total DCAA, DFAA, and PAA concentrations peaked on
average in spring (min. in summer). On average, the contribution of
DCAA-nitrogen (median of 3.44%) to dissolved organic nitrogen was
5-fold higher than that of DFAA-nitrogen (median of 0.60%). Correlation
analyses of AAs with ozone, nitrogen dioxide, and the quantitative
degradation index suggest that DC(/F)AAs are linked with both abiotic
and biological degradation of proteinaceous matter. Moreover, the
high FAA scavenging ratios indicate the presence of postdepositional
degradation of atmospheric proteinaceous matter. Further, the positive
matrix factorization results suggest that the degradation of atmospheric
proteinaceous matter markedly contributes to DCAAs and DFAAs in precipitation.
Overall, the results suggest that the secondary processes involved
in the degradation of atmospheric proteinaceous matter significantly
promote direct bioavailability of AA-nitrogen.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.