Production of H2 in the photocatalytic reactions of ethane on TiO2-supported noble metals

• Photocatalytic decomposition of C2H6.
• TiO2-supported Pt metals.
• Production of hydrogen by illumination.
• Role of the electronic interaction in the support effect.

The effect of illumination on the adsorption and reaction of ethane was investigated on TiO2 and TiO2-supported Pt metals. IR studies showed that new absorption bands developed as a result of illumination of the catalysts. The photocatalytic decomposition of ethane was very limited on pure TiO2: the conversion was only ∼4% at 300 K in 210 min. Deposition of Pt metals onto TiO2 markedly enhanced the rate of photo-induced decomposition of C2H6. Highest conversion of C2H6, 23.5%, was measured over Pt/TiO2 and the turnover frequency was also the highest on this catalyst. Addition of CO2 to ethane exerted no influence on the photocatalysis of ethane. Surprisingly, the main gaseous product of the photocatalytic reaction is H2 with a small amount of CH4. Ethylene was not detected even in traces, indicating the complete degradation of C2H6 to H2 and carbon containing deposit. Temperature programmed reduction (TPR) revealed that the carbonaceous deposit on the catalysts is very stable. On Rh/TiO2 it reacted with H2 to give CH4 (Tp = 453 and 604 K), C2H6 and C3H8 (Tp = 602 K). Similar values were found on Pt/TiO2. The promoting effect of metals was explained by a better separation of charge carriers induced by illumination and by the enhanced electronic interaction between metals and TiO2.

Photocatalytic reaction of C2H6 on various catalysts. TiO2 (A). Formation of H2 (B).Figure optionsDownload as PowerPoint slide