Photocatalytic Overall Water Splitting Promoted by an α-β phase Junction on Ga2O3

Direct overall water splitting with semiconductor-based photocatalysts is one of the most ideal routes for hydrogen production using solar energy. However, most of the semiconductor photocatalysts thus far investigated show only low activity for overall water splitting, the simultaneous splitting of water into H2 and O2. One of the key issues related to this problem is the limited charge separation efficiency upon photo-excitation, which largely depends on the intrinsic electronic and structural properties of semiconductors. To improve the photocatalytic activity of overall water splitting, it is highly desirable to develop approaches that can efficiently promote charge separation in semiconductor based photocatalysts. Fabrication of junctions (such as p-n junctions) between different semiconductors has been demonstrated to be an effective strategy for promoting charge separation in photovoltaics. Proper junctions formed in semiconductor-based photocatalysts could also lead to enhanced activity in either hydrogen or oxygen half reactions.[ 5] However, fabricating efficient junctions for the overall water splitting reaction still remains a challenge. More importantly, the essential relation between the junction and the photocatalytic activity is far less well understood. An indepth understanding of junction-related issues may be a great aid in the design and preparation of efficient semiconductor based photocatalysts. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.