Photocatalytic Activity of Ga 2 O 3 Supported on Al 2 O 3 for Water Splitting and CO 2 Reduction

Abstract

We have examined the photocatalytic activity of Ga 2 O 3 supported on Al 2 O 3 (Ga 2 O 3 /Al 2 O 3 catalyst) without a noble metal cocatalyst for water splitting and reduction of CO 2 with water under UV light irradiation by changing the loading amount of Ga 2 O 3 . All prepared Ga 2 O 3 /Al 2 O 3 catalysts show photocatalytic activities for both water splitting and CO 2 reduction, and their activities are significantly improved compared to those of nonsupported Ga 2 O 3 and Al 2 O 3 . The water splitting is dominated for Ga 2 O 3 /Al 2 O 3 with less than 1.0 vol % of Ga 2 O 3 loaded, whereas the CO 2 reduction, for higher Ga 2 O 3 -loaded samples (2.6, 4.2 vol %). Crystalline structure characterizations of Ga 2 O 3 /Al 2 O 3 catalysts indicate that active sites for both reactions are different. The water splitting proceeds on nanometer-sized Ga 2 O 3 rods dispersed on an Al 2 O 3 support consisting of a little distorted α-Ga 2 O 3 phase. On the other hand, the CO 2 reduction proceeds on sub-micrometer-sized Ga 2 O 3 particles consisting of mixed phases of α-Ga 2 O 3 and γ-Ga 2 O 3 or with appearance of boundaries between the α and γ phases, which plays a critical role. Al 2 O 3 used as the support of the Ga 2 O 3 particles does not seem to play an important role in the photocatalytic CO 2 reduction.