The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

Alloy negative electrodes for Li-ion batteries.

Microbatteries with dimensions of tens to hundreds of micrometers that are produced by common microfabrication techniques are poised to provide integration of power sources onto electronic devices, but they still suffer from poor cycle lifetime, as well as power and temperature range of operation issues that are alleviated with the use of supercapacitors. There have been a few reports on thin-film and other micro-supercapacitors, but they are either too thin to provide sufficient energy or the technology is not scalable. By etching supercapacitor electrodes into conductive titanium carbide substrates, we demonstrate that monolithic carbon films lead to a volumetric capacity exceeding that of micro- and macroscale supercapacitors reported thus far, by a factor of 2. This study also provides the framework for integration of high-performance micro-supercapacitors onto a variety of devices.

https://science.sciencemag.org/content/sci/328/5977/480.full.pdf

Monolithic Carbide-Derived Carbon Films for Micro-Supercapacitors

Achieving mastery over the synthesis of metal nanocrystals has emerged as one of the foremost scientific endeavors in recent years. This intense interest stems from the fact that the composition, size, and shape of nanocrystals not only define their overall physicochemical properties but also determine their effectiveness in technologically important applications. Our aim is to present a comprehensive review of recent research activities on bimetallic nanocrystals. We begin with a brief introduction to the architectural diversity of bimetallic nanocrystals, followed by discussion of the various synthetic techniques necessary for controlling the elemental ratio and spatial arrangement. We have selected key examples from the literature that exemplify critical concepts and place a special emphasis on mechanistic understanding. We then discuss the composition-dependent properties of bimetallic nanocrystals in terms of catalysis, optics, and magnetism and conclude the Review by highlighting applications that h...

Bimetallic Nanocrystals: Syntheses, Properties, and Applications

Detection of hazardous volatile organic compounds (VOCs) by metal oxide nanostructures-based gas sensors: A review

Do We Have Any Alternative for Pt or Pt−Ru? Nitul Kakati,† Jatindranath Maiti,† Seok Hee Lee,† Seung Hyun Jee,† Balasubramanian Viswanathan,*,‡ and Young Soo Yoon*,† †Department of Chemical Engineering, Gachon University, 1342 Seongnamdaero, Sujeong-gu, Seongnam-si, Gyeonggi-do 461-701, Republic of Korea ‡National Centre for Catalysis Research, Department of Chemistry, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India

Anode Catalysts for Direct Methanol Fuel Cells in Acidic Media: Do We Have Any Alternative for Pt or Pt–Ru?

Thickness dependency of sol-gel derived ZnO thin films on gas sensing behaviors

Where do poly(vinyl alcohol) based membranes stand in relation to Nafion ® for direct methanol fuel cell applications?

Corrosion and electrical properties of CrN- and TiN-coated 316L stainless steel used as bipolar plates for polymer electrolyte membrane fuel cells

Vertically aligned ZnO nanorods were grown on flexible polyimide films by a thermolysis assisted chemical solution method to fabricate an ethanol sensing material. Flexible ZnO nanorod sensors were examined to monitor ethanol gas by varying the working temperature from 300 to 125°C and by changing the ethanol concentration in a range from 100 to 10 ppm in synthetic air. A flexible ZnO nanorod sensor can detect 100 ppm of ethanol gas with a sensitivity of 3.11 at 300°C. When compared with ZnO nanorod sensors fabricated on a silicon dioxide hard substrate, its sensing performance exhibited competitive sensitivity.

http://esl.ecsdl.org/content/13/11/J125.full.pdf

Seung Hyun Jee

Papers

Anode Catalysts for Direct Methanol Fuel Cells in Acidic Media: Do We Have Any Alternative for Pt or Pt–Ru?

Thickness dependency of sol-gel derived ZnO thin films on gas sensing behaviors

Where do poly(vinyl alcohol) based membranes stand in relation to Nafion ® for direct methanol fuel cell applications?

Corrosion and electrical properties of CrN- and TiN-coated 316L stainless steel used as bipolar plates for polymer electrolyte membrane fuel cells

Vertically Aligned ZnO Nanorod Sensor on Flexible Substrate for Ethanol Gas Monitoring