Hydrogen Production from Methanol over Gold Supported on ZnO and CeO2 Nanoshapes

In the present study we have found that gold supported on CeO2 and ZnO with well-defined crystal structures or shapes is an excellent catalyst for the low-temperature (175-225 degrees C) steam reforming of methanol (SRM). We have compared the active nature of gold dispersed on {0001} surfaces of ZnO nanorods and polyhedra to our previous work, which demonstrates that TEM-invisible gold dispersed on the {110} surfaces of CeO2 catalyzes the SRM reaction in a cooperative mechanism with CeO2. Similar to Au-CeO2, we have found that Au-O bonds are essential species for SRM over Au-ZnO and the same apparent activation energy (110-120 kJ . mol(-1)) of the reaction was calculated for both catalysts. On the basis of temperature-programmed surface reaction/mass spectrometry analysis, we determined that the SRM reaction on both Au-ZnO and Au-CeO2 involves methanol dehydrogenation, methyl formate hydrolysis, and formic acid decomposition steps to produce CO2 and H-2. Better than 95% catalyst selectivity to CO2 was found over the temperature range from 175 to 250 degrees C for both catalysts. In the presence of methanol, the water-gas shift reaction is suppressed and is not part of the mechanism at temperatures below 250 degrees C. The SRM stability of the Au-ZnO and Au-CeO2 systems is good for practical application of this type catalyst.