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Synthesis of Carbon Aerogel Supported Co-Based Pemfc Catalysts Using Supercritical Ammonia

Alevtina Smirnova1, Yan-Ling Hu1, Mark Aindow1, Daniel Gouberman1, Pete Menard1, and Wendell Rhine2. (1) Cmbe, UCONN, 44 Weaver rd. Unit 5233, Storrs, CT 06269-5233, (2) Aspen Aerogels, 30 Forbes Rd Building B, Northborough, MA 01532

Chemical treatment of four different Co-containing macrocycles impregnated into the carbon aerogel (CA) structure was performed in supercritical ammonia (scNH3). The XPS and XRD results indicated chemical changes of the CA support and Co-containing macrocycles. XPS spectra of unmodified CA demonstrated a presence of two oxygen O(1s) groups and five carbon C(1s) groups in deconvoluted spectra. Chemical acidic (HNO3) or basic (NH4OH) treatment revealed nitrogen N(1s) which had a 1.5eV higher binding energy than nitrogen introduced supercritically in the temperature range of 140-200oC and 2000psi.

Among four studied Co-containing macrocycles only (1R,2R)-(-)-1,2-Cyclohexanediamino-N,N'-bis(3,5-di-t-butylsalicylidene)cobalt(II) showed solubility in scNH3. However, chemical changes of the macrocycle structure after scNH3 treatment were revealed for all four compounds. Sintering of CA impregnated with Co-methoxy-tetra-phenylporfirin (Co-MTOP) at 700 and 900oC in N2 demonstrated a presence of Co-metal nano particles with 20nm in diameter. HRTEM and diffraction patterns of the Co nano-particles showed a "-Co FCC structure with {111} <110> micro-twins. The electrochemical properties of the Co-based CA supported catalysts sintered at 900oC and tested in sulfuric and perchloric acid solutions were evaluated by rotating disc electrode (RDE) and demonstrated catalytic activity in hydrogen oxidation and oxygen reduction reactions.