With rapid development of industrial processes

in particular more recently influenced by “Haze”

air quality draws more and more attentions. A refill of oxygen in air is one of crucial solutions to improve air quality. In contrast to conventional technologies for oxygen production (i.e. physical separation of air

chemical reactions

water electrolysis)

the innovative technology of electrochemical continuous separation of oxygen from air 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. This technology involves two crucial components of polymer electrolyte fuel cells and solid polymer electrolyte water electrolysis (abbreviated as fuel cell and electrolyzer). In this article

the effect of operation conditions on single cell performance such as operation temperature

reactant gases utilization ratios

relative humidity and pressure

etc. for fuel cell was investigated

as well as the ways of water supply (at anode and/or cathode)

water flow rate and operation temperature

etc. for electrolyzer. In terms of fuel cell

the polarization curve was measured

the electrochemical impedance spectra were conducted and the ionic conductivity and activation energy of Nafion® membrane were calculated. Polarization curve was fitted to obtain intrinsic parameters including Tafel slope

exchange current density of oxygen reduction reaction (i0) and m

n

related to mass transfer etc. It showed that the optimum of fuel cell was under 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) and 41.4 mS·cm-1 of ionic conductivity. The Tafel slope slightly varied with temperature

ca. 120 mV·dec-1

but was influenced by the relative humidity. The relative humidity remarkably affected the fuel cell performances. In electrolyzer

the optimum was under conditions of 65℃ of operation temperature

1.08 ohm·cm2 of cell areal resistance and 11.7 mS·cm-1 of ionic conductivity. The effect of water flow rate on performance was negligible. The ways of water supply follow an order of both anode and cathode≈anode>cathode. Under above conditions

activation energies of Nafion®211 and Nafion®115 membranes were calculated as 3.75 and 4.61 kJ·mol-1

respectively. Based on the optimum of single cell performances of fuel cell and electrolyzer

in this article

the preliminary experimental data were provided for the subsequent implementation of scale up of cell stack system for oxygen production.