Influence of Copper as a Co-Catalyst of Potassium Hexaniobate Nanotubes on the Photocatalytic Hydrogen Evolution from a Methanol Aqueous Solution

Abstract

In the presence of Cu2+ ions, the photocatalytic hydrogen evolution from a methanol aqueous solution was achieved when potassium hexaniobate nanotubes were used as the catalyst. It was found that there existed a photo-induced period in the initial reaction stage. Furthermore, the photo-induced period was prolonged by increasing the amount of Cu2+ ions. After that, the rate of hydrogen evolution was dramatically improved. Combined with the reaction phenomena and the result of the photocatalytic hydrogen evolution, it was deduced that the Cu2+ ions captured the photo-generated electrons of potassium hexaniobate nanotubes in the photo-induced period. Consequently, the Cu2+ ions were reduced and deposited on the potassium hexaniobate nanotubes. When the mass ratio of Cu to potassium hexaniobate nanotubes was 3 wt%, the rate of hydrogen evolution over the catalyst reached 21.9 mmol·g-1·h-1, which could almost match with Pt as a co-catalyst. These results showed that Cu was an effective alternative to Pt as a co-catalyst of potassium hexaniobate nanotubes for the photocatalytic hydrogen evolution from the methanol aqueous solution.