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Active non-metal catalysts for the Oxygen Reduction Reaction (ORR) were prepared by decomposition of acetonitrile vapor at 900°C over a pure alumina support, and supports containing 2 wt% Fe or 2 wt% Ni on alumina. The exposed alumina and metal in the samples were subsequently washed away with HF acid to purify the solid carbon material. The sample prepared with iron was the most active sample for the ORR, with only 100 mV greater overpotential than a commercial 20 wt% Pt / Vulcan Carbon catalyst. However, nitrogen-containing carbon deposited on pure alumina (which contained less than 1 ppm metal contamination) was also quite active, demonstrating that platinum or iron is not required for ORR activity. Characterization by XPS and TEM revealed that the more active samples had nanostructured carbon with more edge plane exposure than the less active tube structures formed from the nickel sample.

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A photostable p-type NiO photocathode based on a bifunctional cyclometalated ruthenium sensitizer and a cobaloxime catalyst has been created for visible-light-driven water reduction to produce H2. The sensitizer is anchored firmly on the surface of NiO, and the binding is resistant to the hydrolytic cleavage. The bifunctional sensitizer can also immobilize the water reduction catalyst. The resultant photoelectrode exhibits superior stability in aqueous solutions. Stable photocurrents have been observed over a period of hours. This finding is useful for addressing the degradation issue in dye-sensitized photoelectrochemical cells caused by desorption of dyes and catalysts. The high stability of our photocathodes should be important for the practical application of these devices for solar fuel production.

Noble-metal-free active catalysts for the oxygen reduction reaction (ORR) in an acidic environment were prepared from the pyrolysis of acetonitrile at 900 degrees C over alumina and metal-doped alumina. This work includes analyses of the nitrogen-doped carbon preparation process, characterization of the carbon materials formed, and activity testing for the ORR. The nitrogen-containing carbon nanostructures that formed during the pyrolysis of acetonitrile could be purified by washing the product with hydrofluoric acid. A wide range of techniques were used to characterize the solid carbon products of the acetonitrile decomposition. While the samples have many similar physical properties, X-ray photoelectron spectroscopy and transmission electron microscopy showed evidence that differences in the nanostructure and surface functional groups of the samples are likely to account for observed differences in oxygen reduction activity. The most active catalysts were prepared over alumina impregnated with up to 2 wt % Fe, although the catalysts that were prepared by acetonitrile pyrolysis over alumina with no metal doping still had significant activity. In comparison to a 20 wt % platinum on Vulcan carbon catalyst, the most active samples only have an additional 100 mV overpotential. The selectivity of the catalysts for complete oxygen reduction to water followed a trend similar to activity. The best selectivity to water versus peroxide obtained was 99%, or equivalently, an n of 3.98 (i.e., 3.98 electrons transferred out of a maximum of 4 electrons per mole of oxygen that is reduced), as determined by rotating ring-disk electrode testing.

Nitrogen-containing carbon nanostructure (CN x ) catalysts developed by acetonitrile pyrolysis have been studied to better understand their role in the oxygen reduction reaction (ORR) in PEM and direct methanol fuel cell environments. Additional functionalization of the CN x catalysts with nitric acid has the ability to improve both the activity and selectivity towards ORR.

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The role that nanostructure plays in carbon-based oxygen reduction reaction (ORR) catalysts is unclear. In this publication, the role that graphitic edge plane exposure in carbon-based ORR catalysts was examined using two types of nanofibers: one with high edge plane exposure and one with minimal edge plane exposure. These nanofibers were grown, acid oxidized, and then treated with ammonia to incorporate nitrogen. They were characterized using electron microscopy, hydrophobicity imaging, X-ray photoelectron spectroscopy, and temperature-programmed oxidation experiments to verify their nanostructure, surface species, and overall composition. Rotating ring disk electrode experiments were performed to study their activity for ORR. It was found that nanostructure on its own is not a factor for improved ORR activity. Rather, nanofibers with high edge plane exposure, like stacked platelets, provide the appropriate locations for nitrogen to incorporate into the graphitic matrix. It was also found that gross nitrogen content did not play a role in ORR activity. Nitrogen had to be incorporated into the graphitic matrix, not attached as part of a surface functional group.