Metal−organic frameworks (MOFs), also known as coordination polymers or coordination networks (self-assembled by multidentate organic ligands and metal ions/metal clusters), are multifunctional materials, which have been widely used in the fields of sensing, catalysis, ion exchange, adsorption/separation, or gas storage since their birth. At present, MOFs are a new type of energy storage and conversion material, which are considered as one of the most promising electrode candidates as a result of their large specific surface area, adjustable pores, open metal sites, and adjustable crystal structure. Although MOFs have the above advantages, the direct utilization of pristine MOFs as electrode materials is facing great challenges, which hinder their practical application. On the basis of this, in this review, we summarize the recent development of pristine MOFs as electrode materials for supercapacitors. On the basis of the research of these pristine MOFs, the synthesis process, energy storage performance, and structural design characteristics are summarized. Finally, we focus on the future development trend of pristine MOFs.
We report gallium
(Ga) coating as a simple approach to convert
most common microfluidic substrates to nonwetting surfaces against
surface-oxidized gallium-based liquid metal alloys. These alloys are
readily oxidized in ambient air and adhere to almost all surfaces,
which imposes significant challenges in mobilizing liquid metal droplets
without leaving residue. Various flat substrates (e.g., PDMS, Si,
SiO2, SU-8, glass, and parylene-C coated PDMS) were coated
with thin film (75–200 nm in thickness) of gallium by evaporation
and the coated gallium formed nanoscale uneven and rough surface through
Ostwald ripening with its surface covered with oxide shell. Static
and dynamic contact angles of the gallium-coated surfaces were
found to be greater than 160°, while dynamic contact angle measurements
showed contact angle hysteresis in the range of 6.5–24.4°.
Surface-oxidized gallium-based liquid metal alloy droplets were shown
to bounce off and roll on the gallium-coated surfaces without leaving
any residue which confirms the nonwettability of the gallium-coated
flat surfaces. Scanning electron microscopy (SEM) and atomic force
microscopy (AFM) showed the gallium-coated flat substrates consist
of nanoscale hemispherical structures with average surface roughness
of 33.8 nm. Pneumatic actuation of surface-oxidized liquid metal droplets
in PDMS microfluidic channels coated with gallium was conducted to
confirm the feasibility of utilizing gallium coating as an effective
surface modification for surface-oxidized gallium-based liquid metal
droplet manipulation.
This paper investigates the effect of oxygen flow rates on the performance of the resistive random access memory (RRAM) of indium-tin-oxide (ITO)/ITO(O2)/TiN configuration. By using a co-sputtering deposition system with oxygen gas at different flow rates, oxygen-rich ITO thin films, such as the RRAM switching layer, can be realized. The relationship between oxygen flow rates and electrical characteristics is provided in this research. Further, the material analyses indicate that the oxygen exhibits different bonding characteristics. As a result, the device with the lower oxygen flow rate has better electrical characteristics and reliability. In addition, to explain the experimental results, the Schottky emission conduction mechanism for the high-resistance state and the Ohmic conduction mechanism for the low-resistance state are determined through the current fitting results, and appropriate models are proposed.
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