Trent Molter

Pyrolytic Decomposition of Ammonia Borane to Boron Nitride

The thermal decomposition of ammonia borane was studied using a variety of methods to qualitatively identify gas and remnant solid phase species after thermal treatments up to 1500 °C. At about 110 °C, ammonia borane begins to decompose yielding H(2) as the major gas phase product. A two step decomposition process leading to a polymeric -[NH═BH](n)- species above 130 °C is generally accepted. In this comprehensive study of decomposition pathways, we confirm the first two decomposition steps and identify a third process initiating at 1170 °C which leads to a semicrystalline hexagonal phase boron nitride. Thermogravimetric analysis (TGA) was used to identify the onset of the third step. Temperature programmed desorption-mass spectroscopy (TPD-MS) and vacuum line methods identify molecular aminoborane (H(2)N═BH(2)) as a species that can be released in appreciable quantities with the other major impurity, borazine. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to identify the chemical states present in the solid phase material after each stage of decomposition. The boron nitride product was examined for composition, structure, and morphology using scanning Auger microscopy (SAM), powder X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). Thermogravimetric Analysis-Mass Spectroscopy (TGA-MS) and Differential Scanning Calorimetry (DSC) were used to identify the onset temperature of the first two mass loss events.

Influence of Formic Acid Impurity on Proton Exchange Membrane Fuel Cell Performance

The effect of trace amounts of formic acid (HCOOH) in hydrogen fuel on proton exchange membrane fuel cell (PEMFC) performance is reported. Long-term stability tests (100 h), periodic cyclic voltammetry scans, and electrochemical impedance spectroscopy analyses are used to evaluate and characterize the effects of this impurity on fuel cell performance. The results show that trace amounts of HCOOH cause degradation in fuel cell performance and significantly contaminate the electrodes. Furthermore, full recovery from the contamination could not be achieved by applying pure hydrogen to the anode while operating the fuel cell. However, this degradation may also be caused by the coarsening or dissolution of Pt, in addition to any permanent effects of HCOOH contamination. Mechanisms of contamination of the electrodes and performance degradation of the PEMFC are also postulated.

Contamination of Membrane-Electrode Assemblies by Ammonia in Polymer Electrolyte Fuel Cells

Contamination of polymer electrolyte fuel cell (PEFC) membranes and catalyst layers with ammonia (NH3) is studied experimentally and computationally. Cyclic voltammetry (CV) scans and electrochemical impedance spectroscopy (EIS) analyses show that trace amounts of ammonia can significantly contaminate both the polymer electrolyte membrane (PEM) and the catalyst layers. The results show that the catalyst layer contamination can be reversed under certain conditions, while the membrane recovery tends to be much slower, and permanent effects of ammonia contamination is observed.

Renewable energy for sustainable ocean sensors and platforms

In the future, networks of unmanned and unattended sensor systems will replace many of these manned assets and will become pervasive and highly connected in many maritime areas. Unmanned mobile surveillance systems will be able to operate with a high degree of autonomy and weather tolerance with minimum cost and manpower risk. Low cost, highly sustainable underwater power sources, for both stationary sensors systems and mobile surveillance platforms, are required for this vision. This paper presents a description of interim results of investigations into technologies and systems for generating renewable energy from coastal and open ocean areas. A range of technologies have been investigated from low power systems deriving energy from the microbial fuel cells and the direct bacterial conversion of methane gas to methanol liquid to larger power systems deriving energy from ocean waves, methane hydrate deposits, and hydrothermal vents.

Sustainable unattended sensors for security and environmental monitoring

This paper describes two ocean energy harvesting approaches and technologies for providing sustainable power for distributed unattended sensor and unmanned underwater vehicle networks in open ocean and in coastal and riverine areas. Technologies and systems described include energy harvesting using bottom mounted microbial fuel cells and energy harvesting from naturally occurring methane and methane hydrate deposits. The potential continuous power that could be extracted using these methods ranges from milliwatts for very small microbial fuel cells to tens of kilowatts for methane hydrate processing systems. Exploiting the appropriate naturally occurring ocean or coastal energy source will enable the placement and use of large networks of unattended sensors, both fixed in position and on rechargeable unmanned undersea vehicles. The continuous operation of such systems will have a profound impact on our knowledge of marine biological, physical and chemical processes and systems and will also facilitate improved homeland security and port surveillance.