Advanced Electrodes for Solid Acid Fuel Cells by Platinum Deposition on CsH_(2)PO_4

We demonstrate cathodes for solid acid fuel cells fabricated by vapor deposition of platinum from the metalorganic precursor Pt(acac)_2 on the solid acid CsH_(2)PO_4 at 210 °C. A network of platinum nanoparticles with diameters of 2−4 nm serves as both the oxygen reduction catalyst and the electronic conductor in the electrode. Electrodes with a platinum content of 1.75 mg/cm^2 are more active for oxygen reduction than previously reported electrodes with a platinum content of 7.5 mg/cm^2. Electrodes containing <1.75 mg/cm^2 of platinum show significantly reduced catalytic activity and increased ohmic resistance indicative of a highly discontinuous catalytic-electronic platinum network

Evolution of microscopic heterogeneity and dynamics in choline chloride-based deep eutectic solvents

Deep eutectic solvents (DESs) are an emerging class of non-aqueous solvents that are potentially scalable, easy to prepare and functionalize for many applications ranging from biomass processing to energy storage technologies. Predictive understanding of the fundamental correlations between local structure and macroscopic properties is needed to exploit the large design space and tunability of DESs for specific applications. Here, we employ a range of computational and experimental techniques that span length-scales from molecular to macroscopic and timescales from picoseconds to seconds to study the evolution of structure and dynamics in model DESs, namely Glyceline and Ethaline, starting from the parent compounds. We show that systematic addition of choline chloride leads to microscopic heterogeneities that alter the primary structural relaxation in glycerol and ethyleneglycol and result in new dynamic modes that are strongly correlated to the macroscopic properties of the DES formed

Polystyrene‐based anion exchange membranes via click chemistry: improved properties and AEM performance

Polystyrene-based anion exchange membranes (AEMs) have been fabricated using in situ click chemistry between azide and alkyne moieties introduced as side groups on functionalized polymers. The membrane properties such as water uptake, swelling ratio and conductivity were affected by the number of cations and the degree of crosslinking. The membranes containing a larger amount of trimethylammonium cationic groups (i.e. higher ion exchange capacity) showed high hydroxide conductivity when immersed in KOH solution, exhibiting a peak in conductivity (156 mS cm−1) in 3 mol L–1 KOH solution. A higher degree of crosslinking tended to decrease conductivity. These membranes demonstrated relatively good stability in 8 mol L–1 KOH at 60 °C and maintained 33%–62% of initial conductivity after 49 days with most of the loss in conductivity occurring in early stages of the test. In an alkaline fuel cell, the areal specific resistance was constant indicating good stability of the membranes. The observed peak power density (157 mW cm−2) was comparable to that of other AEM-based fuel cells reported. © 2018 Society of Chemical Industry

Polystyrene-based anion exchange membranes via click chemistry: improved properties and AEM performance

Polystyrene-based anion exchange membranes (AEMs) have been fabricated using in situ click chemistry between azide and alkyne moieties introduced as side groups on functionalized polymers. The membrane properties such as water uptake, swelling ratio and conductivity were affected by the number of cations and the degree of crosslinking. The membranes containing a larger amount of trimethylammonium cationic groups (i.e. higher ion exchange capacity) showed high hydroxide conductivity when immersed in KOH solution, exhibiting a peak in conductivity (156 mS cm−1) in 3 mol L–1 KOH solution. A higher degree of crosslinking tended to decrease conductivity. These membranes demonstrated relatively good stability in 8 mol L–1 KOH at 60 °C and maintained 33%–62% of initial conductivity after 49 days with most of the loss in conductivity occurring in early stages of the test. In an alkaline fuel cell, the areal specific resistance was constant indicating good stability of the membranes. The observed peak power density (157 mW cm−2) was comparable to that of other AEM-based fuel cells reported. © 2018 Society of Chemical Industry

Effect of morphology on anion conductive properties in self-assembled polystyrene-based copolymer membranes

Polystyrene (PS) based random and block copolymers with trimethylammonium and azide side groups are synthesized via nitrogen mediated living radical polymerization. Anion exchange membranes (AEMs) are fabricated from the synthesized copolymers with hydrophobic and hydrophilic dialkyne crosslinkers using Click reaction. Morphological analysis by SAXS and TEM reveals the formation of ordered spherical nanostructure in the block copolymer membranes. In comparison with AEMs from the random copolymer, the block membranes show superior conductivity in higher KOH solutions despite their lower original IEC. The highest conductivity is obtained in 3 M KOH. No significant increase of water absorption or swelling is observed at elevated temperatures for any of the membranes, indicating their good mechanical integrity. No physical degradation is observed for the block membranes after 63 days in 8 M KOH at 60 °C. Fuel cell testing reveals that the block copolymer membranes with well-ordered nanostructure maintained better performance after 10 polarization curves compared to the commercially available AEM (A201)

MEMS-Based Force-Detected Nuclear Magnetic Resonance (FDNMR) Spectrometer

Nuclear Magnetic Resonance (NMR) spectroscopy allows assignment of molecular structure by acquiring the energy spectrum of nuclear spins in a molecule, and by interpreting the symmetry and positions of resonance lines in the spectrum. As such, NMR has become one of the most versatile and ubiquitous spectroscopic methods. Despite these tremendous successes, NMR experiments suffer from inherent low sensitivity due to the relatively low energy of photons in the radio frequency (rt) region of the electromagnetic spectrum. Here, we describe a high-resolution spectroscopy in samples with diameters in the micron range and below. We have reported design and fabrication of force-detected nuclear magnetic resonance (FDNMR)