The vapor-phase decomposition of formic acid was studied over Au supported on various materials, with the aim of producing COfree H 2. With regards to the decomposition and H 2 formation, Au/SiO 2 was found to be the most active catalyst. The reaction started at 373 K and was complete at 523 K. Depending on the nature of the supports, significant differences were experienced in the reaction pathways. On Au deposited on SiO 2 , CeO 2 , and carbon Norit, dehydrogenation predominated, whereas on Al 2 O 3 , ZSM-5, and TiO 2-supported Au, dehydration of formic acid was favored. Pure CO-free H 2 was obtained on Au/SiO 2 and Au/CeO 2 at and below 473 K. No changes in activity or selectivity were observed within ∼10 h. For most of the catalysts, the selectivity was improved by the addition of water to formic acid. In situ infrared spectroscopic studies revealed the formation of formate species even on Au/SiO 2 , located exclusively on Au particles. The decomposition of HCOOH over Au/SiO 2 followed zero-order kinetics. The activation energy for the decomposition was 60.7 kJ mol À1 , and that for H 2 production was 58.5 kJ mol À1 .

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The adsorption and reactions of methanol have been investigated on Au metal supported by various oxides and carbon Norit of high surface area. Infrared spectroscopic studies revealed the dissociation of methanol at 300 K, which mainly occurs on the oxide-supports yielding methoxy species. The presence of Au already appeared in the increased amounts of desorbed products in the TPD spectra. The reaction pathway of the decomposition and the activity of the catalyst sensitively depend on the nature of the support. As regards the production of hydrogen the most effective catalyst is Au/CeO 2 followed

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The adsorption and reactions of dimethyl ether (DME) were investigated on Au nanoparticles supported by various oxides and carbon Norit. Infrared spectroscopic and temperature programmed desorption studies revealed that DME adsorbs readily on most oxidic supports. A limited dissociation of DME to methoxy species was established on Au particles by IR spectroscopy. As regards the formation of hydrogen, Au/CeO 2 is the most effective catalyst. On Au/Al 2 O 3 catalyst the main process was the formation of methanol with a very small amount of hydrogen. Deposition of Au on CeO 2 -Al 2 O 3 mixed oxide resulted in a very active catalyst for H 2 production. The yield for H 2 in the reforming of DME approached the value of 73% at 723-773 K. This feature was explained by the hydrolysis of DME to methanol on alumina, and the fast decomposition of methanol at the Au/CeO 2 interface. Adding potassium promoter to Au/CeO 2 -Al 2 O 3 catalyst further enhanced the production of hydrogen as indicated by the increase of the yield to ∼87%. No deactivation of the catalyst was experienced at 773 K for the measured time, ∼10 h.

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The interaction and the reaction between H 2 + CO 2 have been investigated on supported Au catalysts. By means of infrared spectroscopy, the formation of formate species was detected. The reaction between H 2 + CO 2 occurred above 475-500 K. The main reaction pathway was the formation of CO. The catalytic efficiency of Au sensitively depended upon the nature of the support. Highest conversion of CO 2 was found on Au particles dispersed on n-type oxides, TiO 2 , ZnO, and CeO 2. Au deposited on insulating oxides exhibited much less activity. At higher pressure, at 8.5 atm, a small amount of CH 4 and CH 3 OH were also produced. Illumination of the active catalysts induced the reaction even at room temperature resulting in the formation of CH 4. The high activity of Au particles supported by n-type semiconducting oxides was ascribed to the electronic interaction between Au and oxides leading to the activation of CO 2 .