The recent literature on photochemical and photoelectrochemical reductions of CO 2 is reviewed. The different methods of achieving light absorption, electron-hole separation, and electrochemical reduction of CO 2 are considered. Energy gap matching for reduction of CO 2 to different products, including CO, formic acid, and methanol, is used to identify the most promising systems. Different approaches to lowering overpotentials and achieving high chemical selectivities by employing catalysts are described and compared.

Review: 67 refs.

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A combinatorial approach is described for screening homogeneous CO 2 reduction electrocatalysts by means of a high-throughput 25-well parallel electrolyzer. Active catalysts were then screened by three methods: (1) the presence of CO gas in the electrolyzer head space; (2) a pH change for the individual solutions before and after bulk electrolysis due to proton consumption during CO 2 reduction; and (3) other physical attributes. Based on these screening methods, two solutions out of the 25 were selected for further study. One out of two selected solutions, nickel cyclam, a well-known CO 2 reduction electrocatalyst, was correctly identified to be the most active.

Review: 67 refs.