| With rapid growing of global economy and industrial processes, plenty of problems related to air pollutions appear, in particular more recently influenced by "Haze" in China, air quality draws more and more attentions. A refill of oxygen is one of crucial solutions to improve air quality. This thesis focuses on research and development of electrochemical separation of oxygen from air, which is oxygen extracted from air, by coupling gas supply and combing hydrogen fuel cells and water electrolyzers. In contrast to conventional technologies for oxygen production (i.e. physical separation of air, chemical reactions, water electrolysis), the invented technology of electrochemical continuous separation of oxygen from air (ECSOA) features, separation of pure oxygen from air, high efficiency, continuous operation, environment friendly, silent operation, ease of scale up, and applicability to indoor or outdoor fields.Since polymer electrolyte membrane fuel cells and solid polymer electrolyte water electrolysis (abbreviated as fuel cell and electrolyzer) are crucial to the whole oxygen system. In this thesis, (1) the effect of operation conditions on single cell performance, such as operation temperature, reaction gases utilization ratios, relative humidity and operation pressure etc. for fuel cell was investigated, as well as water supply at anode or cathode, water flow rate and operation temperature etc. for electrolyzer. In terms of fuel cell, polarization curve and power density curve were measured, electrochemical impedance spectra conducted and ionic conductivity and activation energy of Nafion(?) membrane were calculated. From polarization curve, it is fitted to obtain parameters of Tafel slope, exchange current density of oxygen reduction reaction (io) and mass transport related m, n, etc. (2) the effect of hot-pressing parameters on single cell performance such as temperature, length of time and pressure was investigated. (3) the oxygen generating system was explored.The experimental results show that, (1) the optimum of fuel cell are conditions of ambient pressure,60℃ of operation temperature,0.42 W·cm-2 of peak power density,77 mohm·cm2 of cell areal resistance (membrane),41.4 mS·cm-1 of ionic conductivity. Tafel slope slightly varied with temperature, ca.120 mv·dec-1, but was influenced by relative humidity. At the temperature, single cell performance decreased with the gases utilization ratios of fuel and oxidant, but significantly increased with relative humidity. Operation pressure slightly influences single cell performance, of which 0.52 W·cm-2 of peak power density at 0.1 MPa was observed. In electrolyzer, the optimum are conditions of water supply at anode and cathode (similar to water supply at anode),65℃ of operation temperature,1.08 ohm·cm2 of cell areal resistance,11.7 mS·cm-1 of ionic conductivity. The effect of water flow rate on performance was negligible. Under above conditions, activation energies of Nafion(?)211 and Nafion(?)115 membranes were calculated as 3.75 and 4.61 kJ·mol-1, respectively. (2) the optimum hot-pressing conditions of polymer electrolyte membrane fuel cells membrane electrode assembly are 140℃ of hot-pressing temperature,210 s of hot-pressing,3 MPa of pressure. (3) the performance of fuel cell and total oxygen generating rate increased with the current of assistant electrolyzer, air flow rate and relative humidity of air. When the current density of assistant unit was 588 mA·cm-2, air flow rate of fuel cell was 100 mL·min-1, relative humidity of air is 100%, the total oxygen generating rate was 20 mL·min-1, the unit area oxygen generating rate and unit current density oxygen generating rate of fuel cell were calculated as 0.4 mL·min-1·cm-2 and 1.9 mL·cm2·min-1·mA-1. |
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