Subject Of Sustained Interest Research Articles

Reactant Transport Engineering Approach at Cathode to High Power Direct Methanol Hydrogen Peroxide Fuel Cell

The development of high-power fuel cells could advance the electrification of the transportation sector, including marine and air transport. Liquid-fueled fuel cells are particularly attractive for such applications as they obviate the issue of fuel transportation and storage. Herein, we report a direct methanol hydrogen peroxide fuel cell (DMHPFC) for high-power propulsion applications that delivers 0.8 W cm2 peak power density by using a pH gradient-enabled microscale bipolar interface (PMBI) to effectively meet the incongruent pH requirements for methanol oxidation/peroxide reduction reactions.DMHPFCs are an important alternative to hydrogen-fed polymer electrode membrane fuel cell (PEMFCs) and anion exchange membrane fuel cells (AEMFCs) due to methanol’s high energy density compared to that of hydrogen and superior kinetics of hydrogen peroxide reduction reaction as compared to Oxygen. A unit volume of Hydrogen gas stored at a pressure of approximately 69 MPa corresponds to volume-specific energy density of roughly 2.1 kWh/l while 39% volume of aqueous methanol and 41% volume of aqueous hydrogen peroxide corresponds to volume-specific energy density of 9.2 kWh/l. So, DMHPFC’s energy density is approximately four times higher than hydrogen fuel cell’s energy density and is comparable to gasoline which contains roughly 9.2 kWh/l of available bond energy. The theoretical potential for Methanol oxidation reaction (MOR) in basic medium is lower than that in an acidic medium (-0.78 V vs. -0.02 V) and the theoretical potential for the Hydrogen peroxide reduction reaction (HPRR) is higher than that for oxygen reduction (1.77 V vs. 1.23 V in acidic medium). This results in the highest theoretically possible cell voltage for cells with alkaline anodes and acidic cathodes. We achieved sustained operation of the DMHPFC with an alkaline anode and an acidic cathode by incorporating our pH-gradient-enabled microscale bipolar interface (PMBI).However, the system exhibits a relatively low Faradaic efficiency of 50% due to the parasitic evolution of O2 by the decomposition of H2O2. The O2 evolution results in a mixed potential at the cathode due to the occurrence of both the HPRR (E0 = 1.77 V versus standard hydrogen electrode [SHE]) and the oxygen reduction reaction (ORR); (E0 = 1.23 V versus SHE), lowering the overall cell potential. The O2 surface coverage reduces the available sites for the HPRR, effectively deactivating the catalyst. Electrocatalysts exhibiting a combination of high HPRR activity and selectivity (by inhibiting H2O2 decomposition, and hence inhibiting ORR) would result in higher faradic efficiency and have been the subject of sustained interest. Here, we examine an alternate reactant-transport engineering approach to improve the overall cell potential and cell performance of the DMHPFC. Our reactant-transport engineering approach has examined the impact of reactant flowrate, flow velocity, residence time, and flow regime (via the Reynolds number ([Re]) on DMHPFC performance. Balancing the competing demands of high residence time to improve Hydrogen peroxide reduction reaction (HPRR) rates with high flowrates to detach adsorbed O2, we identify a critical Re and Damkholer number (Da) to efficiently exclude O2 gas bubbles while maintaining large current densities during the operation of a DMHPFC. Reactant-transport engineering of the cathode flow field architecture and fuel flowrates mitigates parasitic hydrogen peroxide decomposition and oxygen reduction reactions and lessens cathode passivation by oxygen bubbles. DMHPCs fulfilling these criteria provide a power density of >500 mW cm-2 at 1.0 V compared to state-of-the-art polymer electrolyte membrane fuel cells (PEMFCs) that typically operate at 0.75 V. The high peak power density of 800 mW cm-2 at 1.1 V may offer a pathway to reduce fuel cell stack size for propulsion applications. Our work paves the way for such other liquid fuel cells with hydrogen peroxide as the oxidant and enabled with PMBI resulting in significantly improvement in the performance. Figure 1

Public libraries: political vision versus public demand?

PurposeThe purpose of the paper is to review UK government policy on public libraries since 2003, and to examine its relationship to other forms of demand for public librariesDesign/methodology/approachThe published literature from government and professional bodies is reviewed, alongside published statistics on library use.FindingsSince 2003 public libraries have been the subject of sustained interest from UK government, in the form of a range of policy initiatives and incorporation in the Best Value and more recent Common Area Assessment monitoring frameworks. Alongside this, professional bodies and other commentators have put forward views on the role of libraries, but even taken together it is not clear that these represent the needs or aspirations of library service users.Originality/valueThis paper provides an overview of the demand for UK public libraries, and its synthesis will be of value to librarians, government departments and professionals in this and related fields.

The Musaeum of Alexandria and the Formation of the Muséum in Eighteenth-Century France

The Hellenistic Musaeum of Alexandria became a subject of sustained interest for seventeenth- and eighteenth-century antiquarians and architects. What little documentation remained indicated that the Musaeum had been an élite group of scholars, supported by a library, housing, and other research facilities. In 1793 the French Revolutionary government gave its newly public collections of rare objects the name muséum in reference to the Alexandrian project. However, only one muséum in Paris could sustain the comparison: the Muséum d'Histoire Naturelle. By 1797 it alone retained the name of muséum after the ancient Musaeum; the rest carried the modern title musée.

Experimental study of surface and lattice effects on the solubility of hydroxyapatite.

The of hydroxyapatite (OHAp), Ca5 (PO4) 3OH, has been the topic of many investigations. It has been a subject of sustained interest because the solution behavior of OHAp is fundamental to processes of physiologic adaptation in bone and teeth. However, experimental studies of the soltubility of OHAp often have yielded confusing results. The responsibility for much of this confusion lies with the use of variable and nonrigorous definitions of solubility in the framework of a particular study, and with failure to consider the effect of on the dissolution process. Other factors' that may have caused difficulties include the sensitivity of the apparent of OHAp to impurities, the difficulty involved in the preparation of pure OHAp, and the slow growth of OHAp crystals in solution, which often results in failure to achieve equilibrium with the lattice. Many of these difficulties can be avoided if an internally consistent, thermodynamic treatment for the of OHAp is formulated. This has been done by Brown. Moreno, and Gregory.' Their treatment reveals the importance of separating lattice and surface reactions in the study of the of sparingly soluble salts. Lattice reaction refers to the process where in a local region of a crystal, the stoichiom-