Hydrogen dissociation is a critical step in many hydrogenation reactions central to industrial chemical production and pollutant removal. This step typically utilizes the favorable band structure of precious metal catalysts like platinum and palladium to achieve high efficiency under mild conditions. Here we demonstrate that aluminum nanocrystals (Al NCs), when illuminated, can be used as a photocatalyst for hydrogen dissociation at room temperature and atmospheric pressure, despite the high activation barrier toward hydrogen adsorption and dissociation. We show that hot electron transfer from Al NCs to the antibonding orbitals of hydrogen molecules facilitates their dissociation. Hot electrons generated from surface plasmon decay and from direct photoexcitation of the interband transitions of Al both contribute to this process. Our results pave the way for the use of aluminum, an earth-abundant, nonprecious metal, for photocatalysis.

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Zirconia-supported iron-based Fischer-Tropsch catalysts were prepared using incipient wetness impregnation. The choice of the precursor, in this case the chelating ammonium iron(III) citrate, and the applied calcination temperature determine the final distribution of the precursor on the zirconia support. Several techniques reveal that both an unpromoted and a potassium-promoted catalyst can be prepared, of which the iron(III) oxide exhibits a high dispersion and is, moreover, monodisperse.

The reduction behaviour (the activation process) of two iron-based Fischer-Tropsch catalysts viz. an unpromoted and a potassium-promoted zirconia-supported iron catalyst is investigated. The initial dispersion of both catalysts is very high. To establish the nature of the iron species under hydrogen atmosphere, experiments were performed at ambient pressure. It is demonstrated for both catalysts that during reduction the carbon originating from the citrate complex used in the preparation procedure is not completely removed, whereby the largest amount of the carbon species is encountered on the potassium-promoted catalyst. During reduction at ambient pressure this residual carbon reacts with metallic iron and forms cementite (θ-Fe 3 C). The iron oxide of the potassium-promoted catalyst turns out to reduce more easily than the oxide of the unpromoted catalyst. Upon formation of divalent iron, this divalent species readily reacts with the support to give a stable mixed oxide. This mixed oxide is suggested to be a prerequisite in maintaining a high dispersion of the metallic iron particles. Based on the analyses presented here, a reduction model is proposed.

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