Light-Driven Heterogeneous Reduction of Carbon Dioxide: Photocatalysts and Photoelectrodes

Light-Driven Heterogeneous Reduction of Carbon Dioxide: Photocatalysts and Photoelectrodes

James L. White,† Maor F. Baruch,† James E. Pander III,† Yuan Hu,† Ivy C. Fortmeyer,† James Eujin Park,† Tao Zhang,† Kuo Liao,† Jing Gu,‡ Yong Yan,‡ Travis W. Shaw,† Esta Abelev,† and Andrew B. Bocarsly*,†
† Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States ‡ Chemical and Materials Science Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States

Chemical Reviews: http://pubs.acs.org/doi/pdf/10.1021/acs.chemrev.5b00370
DOI: 10.1021/acs.chemrev.5b00370

Abstract: Although modern photoelectrochemistry is often traced back to 1972 and the report by Honda and Fujishima1 that a TiO2 photoanode in an electrochemical cell caused the splitting of water into O2 and H2 when illuminated, the first report of this type of phenomenon dates back to Becquerel’s studies, published in 1839.2 This makes photoelectrochemistry one of the oldest investigated techniques for the conversion of sunlight into usable energy. Over this time frame, two general types of photoelectrochemical cells have been developed. The first, typified by Honda’s electrochemistry, is focused primarily on the storage of light energy as high-energy chemical products. Initially, this was termed “artificial photosynthesis” and was focused for the most part on splitting water to generate H2 as an environmentally benign fuel. The second type of photoelectrochemical cell utilizes a chemically reversible redox couple that undergoes a redox change of state at the photoelectrode, followed by conversion of the product species back to the reactant at the counter electrode. The net effect of this reaction is a chemically invariant system that generates electricity from light. The initial implementation of the Gratzel cell, which used ̈ a reversible I2/I3 − couple and a dye-sensitized TiO2 photoanode, is an example of this type of system.3 The work under consideration in this paper focuses on the photosynthetic cells and related systems. However, an analysis of these systems, as is more obviously critical to electricity-generating systems, must take into account whether the system is merely catalytic for the reaction of interest or is a system that actually converts light energy into stored chemical energy. Thus, how one parametrizes and evaluates a heterogeneous photoinduced charge transfer process becomes a critical issue that is therefore reviewed in this work.