In this study, various
nitrogen-containing functional groups, namely,
pyridine (N-6), pyrrole (N-5), oxidized N (N–O), and quaternary
N (N-Q), are created on activated carbon (AC) surface via melamine,
ammonia, and nitric oxide doping methods. N-5 and N-6 groups markedly
alter the specific surface area and pore size of AC. N–O is
found to affect electrolyte wettability, and the N-Q content is closely
associated with AC electronic conductivity. The nitrogen-containing
groups do not contribute to pseudocapacitance in propylene carbonate
and acetonitrile electrolytes. However, the nitric-oxide-treated carbon
(AC-NO) exhibits the best high-rate charge–discharge performance
among the investigated materials. The N-Q-enriched and N-5/N-6-depleted
AC-NO most effectively suppresses the leakage current and gas evolution
of supercapacitors. Online gas chromatography is used to analyze the
gaseous species produced from AC electrodes. With an appropriate surface
functionality on carbon, the cell voltage can be increased to ∼3
V, increasing the energy and power densities. The aging behavior of
the carbon electrodes with and without nitrogen modification after
being floated at 2.5 V and 70 °C for 3 days is investigated.
An effective strategy for enhancing supercapacitor performance and
reliability is proposed.
Mg, in the form of MgH2,is one kinds of materials widely used as hydrogen storage materials. Absorption and desorption properties of hydrogen which comes from metal hydride depend on materials itself, addition of elements, as well as manufacturing method. In this research, Mg as hydrogen storage were prepared by mechanical alloying with Ni, Cu, and Al as element addition and variation milling time for 10, 20 and 30 hours. Some morphological analyses (XRD, SEM) were done to observe phase transformation. Absorption and desorption properties characterization were employed by DSC and hydrogenation tests. The improvement in milling time decreased particle size, therefore enhanced wt% of absorbed hydrogen and decrease onset desorption temperature. However, the excessive of agglomeration and cold welding on mechanical alloying process resulted in bigger particle size. Alloying elements, Al and Cu, served as catalyst, while Ni acted as alloying which reacted with hydrogen. Mg10wt%Al with 20 hours milling time at hydrogenation temperature 250°C, 3 atm pressure, and 1 hour holding time resulted in the highest weight percent of H2(0.38%wt). However, Mg10wt%Al with 30 hours milling time had the lowest onset temperature, 341.49°C
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