308
Electrochemical Supercapacitors for Energy Storage and Delivery
crystallite size, defects, and alterations of materials after they undergo certain processes [29–31].
For example, the relationship between pseudocapacitance and heat
treatment temperature of nickel oxide was investigated using XRD, x-ray
absorption spectroscopy, and CV. These techniques can provide important
information about structure arrangements and the electrochemical properties of nickel oxide at various heat treatment temperatures. Similar studies
were performed on composites (graphene–polyaniline, MnO 2 –mesoporous
carbon) [30,31]. XRD can reveal material structures revealing the relationship of electrochemical properties and the effects of certain chemical or
physical alterations.
7.6.4 Energy-Dispersive X-Ray Spectroscopy (EDX)
EDX is commonly used as an addition to SEM, utilizing an electron gun and
imaging equipment to locate the desired sample position. To perform EDX
analysis of a sample, the electron imaging detector is replaced by an x-ray
detector system. As previously noted, an electron beam that hits a sample
produces a variety of signals including characteristic x-rays.
The x-rays are created when the incident electrons cause ejection of an
electron in the inner shell. An outer shell electron fills the hole and releases
the energy difference as an x-ray [32]. The x-ray energy is characteristic of the
atomic structure and the difference between the electron shells. For example,
the P Kα x-ray has an energy level of 2 KeV and is characteristic of a phosphorus atom undergoing a one-shell jump (α) from the L orbital to the K orbital.
The detector collects the x-rays, converting them to voltage before they are
sent for processing and analysis to generate an intensity spectrum.
EDX is a useful tool for ES research, for example, for determining the
atomic dispersion of a sample surface. However, EDX loses measurement
accuracy because of (1) overlapping peaks, (2) detector resolution, and (3)
emission of x-rays in all directions—they must escape the sample before
being reabsorbed to be detected. The third factor can mean lower energy
x-rays are collected with lower intensity than is actually present and rough
morphology can mask elements resulting in inaccurate atomic composition
descriptions [33].
7.6.5 X-Ray Photoelectron Spectroscopy (XPS)
Also known as electron spectroscopy for chemical analysis (ESCA), XPS
utilizes x-rays and photoelectric phenomena to study electronic structure,
compound composition, electron and chemical states, electron bonding, and
surface analysis [34–36]. In practice, a sample is bombarded by a monochromatic single wavelength x-ray beam. This causes core electrons from the
sample to overcome their binding energy and escape to the sample surface
where they are detected [34].
Electrochemical Supercapacitors for Energy Storage and Delivery
crystallite size, defects, and alterations of materials after they undergo certain processes [29–31].
For example, the relationship between pseudocapacitance and heat
treatment temperature of nickel oxide was investigated using XRD, x-ray
absorption spectroscopy, and CV. These techniques can provide important
information about structure arrangements and the electrochemical properties of nickel oxide at various heat treatment temperatures. Similar studies
were performed on composites (graphene–polyaniline, MnO 2 –mesoporous
carbon) [30,31]. XRD can reveal material structures revealing the relationship of electrochemical properties and the effects of certain chemical or
physical alterations.
7.6.4 Energy-Dispersive X-Ray Spectroscopy (EDX)
EDX is commonly used as an addition to SEM, utilizing an electron gun and
imaging equipment to locate the desired sample position. To perform EDX
analysis of a sample, the electron imaging detector is replaced by an x-ray
detector system. As previously noted, an electron beam that hits a sample
produces a variety of signals including characteristic x-rays.
The x-rays are created when the incident electrons cause ejection of an
electron in the inner shell. An outer shell electron fills the hole and releases
the energy difference as an x-ray [32]. The x-ray energy is characteristic of the
atomic structure and the difference between the electron shells. For example,
the P Kα x-ray has an energy level of 2 KeV and is characteristic of a phosphorus atom undergoing a one-shell jump (α) from the L orbital to the K orbital.
The detector collects the x-rays, converting them to voltage before they are
sent for processing and analysis to generate an intensity spectrum.
EDX is a useful tool for ES research, for example, for determining the
atomic dispersion of a sample surface. However, EDX loses measurement
accuracy because of (1) overlapping peaks, (2) detector resolution, and (3)
emission of x-rays in all directions—they must escape the sample before
being reabsorbed to be detected. The third factor can mean lower energy
x-rays are collected with lower intensity than is actually present and rough
morphology can mask elements resulting in inaccurate atomic composition
descriptions [33].
7.6.5 X-Ray Photoelectron Spectroscopy (XPS)
Also known as electron spectroscopy for chemical analysis (ESCA), XPS
utilizes x-rays and photoelectric phenomena to study electronic structure,
compound composition, electron and chemical states, electron bonding, and
surface analysis [34–36]. In practice, a sample is bombarded by a monochromatic single wavelength x-ray beam. This causes core electrons from the
sample to overcome their binding energy and escape to the sample surface
where they are detected [34].