A Study On Electrochemical Oxygen Pump

Electrochemical oxygen pump?EOP? is a kind of electrochemical device based on air electrode for oxygen generation, which can separate oxygen from air driven by electrical potential difference. However, EOPs based on proton exchang membrane suffer from the sluggish oxygen electrode kinetics and high costs of precious metal electrocatalysts, while EOPs based on on alkaline aqueous solution are obsessed by the leakage of electrolyte, electrolyte crystallization during electrolysis, and waste of the solution. In this dissertation, a series of research centered on EOPs were conducted, including the preparation of bi-functional electrocatalysts for oxygen electrode with biomass as a precursor, the synthesis of high strength double network?DN? hydrogel electrolyte and the measurement of EOPs fabricated with different electrocatalysts.A heteroatoms doped carbon?HDC? electrocatalyst was prepared by one step pyrolysis in molten salt with hen's egg yolk as precursor. Nitrogen was in-situ doped into the carbon matrix with a content as high as 5.89 wt.% during pyrolysis, and a small amount of doped phosphorus and sulfur were detected. The XPS results revealed it that Graphitic-N and Pyridinic-N dominated in all four kind of N species. Cyclic voltammetry, linear sweep voltammetry and chronoamperometry were employed on a rotating disk electrode to evaluate the electrocatalytic activity of the HDC catalysts towards the oxygen reduction reaction?ORR? and the oxygen evolution reaction?OER? in alkaline media. The yolk pyrolyzed at 800? not only shows a superior performance to other yolk derived HDC catalysts, but also demonstrates similar ORR activity and higher OER activity and duarability as compared with a commonly used commercial Pt/C catalyst. CoCl2·6H2O, which changed the HDC into porous spongy structure with Co₂ P nanoparticles supported on the inner wall of the bubbles, was mixed into yolk precursor to enhance its ORR activity and OER duarability.Polyacrylamide/polyvinyl alcohol?PAM/PVA? DN hydrogel with high tensile strength was synthesized via a facile pre-mixed two-step crosslink method with acrylamide and PVA as precursors. This could lead to a homogeneous mixture of the two precursors before they crosslinked into a certain shape, and improve the homogeneity of the hydrogel. The as-obtained hydrogel possessed a loosly interchange pore structure, with the elastic modulus more than 50 kPa and the tensile fracture up to 113.4 kPa. Alkaline doped DN hydrogel electrolyte was obtained by immersing the PAM/PVA hydrogel in a KOH solution. The alkaline doped DN hydrogel electrolyte performed a high conductivity reaching the magnitude of 10^-2 S·cm^-1 and a wide electrochemical stabilitywindow, which was ca. 2.0 V, and was expected to find application in fuel cells, electrochemical oxygen pumps and other electrochemical devices.Three different EOPs were fabricated with precious metal catalyst, homemade HDC catalyst pyrolyzed at 800 ? and homemade Co₂P-HDC catalyst as electrocatalyst, respectively. Alkaline doped PAM/PVA DN hydrogel electrolyte membranes were employed as the the electrolyte. The EOP fabricated with homemade Co₂P-HDC catalyst performed a onset potential of 0.587 V, and retained 62 % of its current density after 1 hour of chronoamperometry test with a electrolysis voltage of 1.0 V. It also performed a voltage increasing rate of 2.66 mV·h^-1 at a low current density of 50 mA·cm^-2 during chronopotentiometric test, which is much smaller than that of precious metal catalysts catalyzed EOP.