Experimental Identification of New Photocatalytic Semiconductors for Water Splitting and Carbon Dioxide Reduction

Abstract

The photocatalytic splitting of water and reduction of CO2 by a photostable semiconductor using visible light is an important problem yet to be resolved. An assay to screen for photocatalytic activity of previously uncharacterized materials is created, looking for either H2 or O2 production indicative of water splitting, CO production indicative of CO2 reduction, or H2O2 production. Numerous candidates for water splitting and H2O2 production are found, along with three candidates for CO2 reduction, but many are plagued by low activity or photodecomposition. Promising materials are characterized and synthesized with the goal of increasing activity by doping or varying elemental composition. From these syntheses, a case can be made for photocatalytic selectivity of either hydrogen evolution or CO2 reduction for the CuxTiSe2 (0<x<0.08) series, wherein as the amount of copper is varied, different pathways appear to dominate, with x=0.01 favoring CO2 reduction and x=0.03 favoring water splitting. This material, however, does not have good photostability, especially in basic conditions where it is most active, yielding it an undesirable photocatalyst. With the success of the screening process, numerous pathways for future work are suggested using other candidate materials identified in the assay.