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We demonstrate the first device to our knowledge that uses a solar panel to power the electrochemical reduction of dissolved carbon dioxide (carbonate) into formate that is then used in the same device to operate a direct formate fuel cell (DFFC). The electrochemical reduction of carbonate is carried out on a Sn electrode in a reservoir that maintains a constant carbon balance between carbonate and formate. The electron-rich formate species is converted by the DFFC into electrical energy through electron release. The product of DFFC operation is the electron-deficient carbonate species that diffuses back to the reservoir bulk. It is possible to continuously charge the device using alternative energy (e.g., solar) to convert carbonate to formate for on-demand use in the DFFC; the intermittent nature of alternative energy makes this an attractive design. In this work, we demonstrate a proof-of-concept device that performs reduction of carbonate, storage of formate, and operation of a DFFC., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A device was constructed that converts dissolved carbon dioxide to power. In a central reservoir this device wholly contains the electrochemical conversion cycle of carbonate to formate and formate to carbonate. At one end of the reservoir is a cation exchange membrane containing Sn and Pt catalysts to reduce carbonate and oxidize water, respectively. At the other end is an anion exchange membrane containing Pd and Pt catalysts to oxidize formate and reduce oxygen, respectively (the direct formate fuel cell). The electrochemical reduction of carbonate produced 54 mM formate after 15 min. The formate produced within this device produced a power density of 2 mW cm −2 . The overall efficiency of a 15 min run of this device was 40%. This device represents a two order of magnitude increase in the time efficiency with which carbonate is reduced to formate compared with the first reported device that converts carbon dioxide to power. [ABSTRACT FROM AUTHOR]