Electric power storage in high-energy chemicals, called “energy carriers”, has received much attention for the efficient storage and on-demand supply of renewable electricity. Here, we demonstrate direct power charge using an alcohol/carboxylic acid redox couple. Highly transportable glycolic acid, an alcoholic compound, was successfully produced by 4-electron reduction of oxalic acid, a dicarboxylic acid, using ubiquitous TiO2 catalysts with high efficiency and selectivity (70-95% Faraday efficiency and &gt;98% selectivity) under mild conditions in the potential region of -0.5 to -0.7 V vs. the RHE at 50 °C. Note that few systems achieved electroreduction of a carboxylic acid to produce an alcoholic compound. The most desirable characteristic of this electroreduction is the suppression of hydrogen evolution even in acidic aqueous media (Faraday efficiency of 70–95%, pH 2.1). The detailed observation of TiO2 catalysts using scanning TEM and eels techniques provided a mechanistic insight into this highly selective catalysis, i.e., whole grain of an active catalyst is composed only of an anatase phase while a rutile phase forms on the surface of an inactive one as shown in Fig. 1, which suggests that detailed structural control is significantly predominant in this process. Recently, we succeeded in the production of glycolic acid via the electrochemical reduction of OX and electrooxidation of water with the help of renewable light energy for the first time. Furthermore, we performed electric power generation via the selective electrooxidation of glycolic acid to oxalic acid without CO2 emission—specifically, carbon-neutral power circulation using liquid carriers.

Inorganic nanocatalysts for the electronic power circulation using alcohol/carboxylic acid redox couples

254th National Meeting (2017)

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