Combinatorial materials research can provide valuable insight into the relations between a materials composition, structure and properties of interest, especially when a broad understanding of these relations is lacking. Photocatalytic decomposition of water is one such research area in which the combinatorial process can be useful. The ability to synthesize and characterize many material combinations quickly and inexpensively can be very advantageous when properties of these combinations are unknown. This thesis reports on the construction of a specialized electrochemical test cell designed to measure the photocatalytic properties of novel materials. The experimental setup utilizes various laser wavelengths and externally applied voltages to probe the effective band gap of the semiconductor materials. Furthermore, the results of this study clarify the techniques needed to identify a good photocatalyst and suggest improved experiments which could significantly expand on the current knowledge base. 2|Page