Removing
excess nitrate (NO3
–) from
waste streams has become a significant environmental and health topic.
However, realizing highly selective NO3
– conversion toward N2, primarily via electrocatalytic
conversions, has proven challenging, largely because of the kinetically
uncontrollable NO3
–-to-NO2
– pathway and unfavorable N–N coupling.
Herein, we discovered unique and ultra-high electrocatalytic NO3
–-to-NO2
–activity
on oxide-derived silver (OD-Ag). Up to 98% selectivity and 95% Faradaic
efficiency (FE) of NO2
– were observed
and maintained under a wide potential window. Benefiting from the
superior NO3
–-to-NO2
–activity, further reduction of accumulated NO2
– to NH4
+ was well regulated by the cathodic
potential and achieved an NH4
+ FE of 89%, indicating
a tunable selectivity to the key nitrate reduction products (NO2
– or NH4
+) on OD-Ag.
Density functional theory computations provided insights into the
unique NO2
– selectivity on Ag electrodes
compared with Cu, showing the critical role of a proton-assisted mechanism.
Based on the ultra-high NO3
–-to-NO2
– activity on OD-Ag, we designed a novel
electrocatalytic–catalytic combined process for denitrifying
real-world NO3
–-containing agricultural
wastewater, leading to 95+% of NO3
– conversion
to N2 with minimal NOX gases. In addition to
the wastewater treatment process to N2 and the electrochemical
synthesis of NH3, NO2
– derived
from electrocatalytic NO3
– conversion
can serve as a reactive platform for the distributed production of
various nitrogen products.
A new process has been developed for the selective construction of 2,6-disubstituted, 2,4,6-trisubstituted, and 3,5-disubstituted pyridines based on the catabolism and reconstruction behaviors of amino acids. Molecular iodine was used as a tandem catalyst to trigger the decarboxylation-deamination of amino acids and to promote the subsequent formation of the pyridine products.
A highly efficient I2/Cu(NO3)2·3H2O-mediated triple C(sp(3))-H functionalization reaction for the synthesis of 2,4,5-trisubstituted furans from aryl methyl ketones and rongalite by employing rongalite as a C1 unit has been developed. This method allows rapid access to (2-acyl-4-methylthio-5-aryl) furans. Preliminary mechanistic studies indicate that in situ generated dimethyl(phenacyl)-sulfonium iodine and HCHO were probably the key intermediates in this transformation.
Aqueous zinc‐ion batteries (AZIBs) are regarded as promising electrochemical energy storage devices owing to its low cost, intrinsic safety, abundant zinc reserves, and ideal specific capacity. Compared with other cathode materials, manganese dioxide with high voltage, environmental protection, and high theoretical specific capacity receives considerable attention. However, the problems of structural instability, manganese dissolution, and poor electrical conductivity make the exploration of high‐performance manganese dioxide still a great challenge and impede its practical applications. Besides, zinc storage mechanisms involved are complex and somewhat controversial. To address these issues, tremendous efforts, such as surface engineering, heteroatoms doping, defect engineering, electrolyte modification, and some advanced characterization technologies, have been devoted to improving its electrochemical performance and illustrating zinc storage mechanism. In this review, we particularly focus on the classification of manganese dioxide based on crystal structures, zinc ions storage mechanisms, the existing challenges, and corresponding optimization strategies as well as structure–performance relationship. In the final section, the application perspectives of manganese oxide cathode materials in AZIBs are prospected.
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