Efficient Photoelectrochemical Reduction of Carbon Dioxide to Formic Acid: A Functionalized Ionic Liquid as an Absorbent and Electrolyte.

Photoelectrochemical (PEC) reduction of carbon dioxide (CO2 ) is a potential method for production of fuels and chemicals from a C1 feedstock accumulated in the atmosphere. However, the low solubility of CO2 in water, and complicated processes associated with capture and conversion, render CO2 conversion inefficient. A new concept is proposed in which a PEC system is used to capture and convert CO2 into formic acid. The process is assisted by an ionic liquid (1-aminopropyl-3-methylimidazolium bromide) aqueous solution, which functions as an absorbent and electrolyte at ambient temperature and pressure. Within this PEC reduction strategy, the ionic liquid plays a critical role in promoting the conversion of CO2 to formic acid and suppressing the reduction of H2 O to H2 . At an applied voltage of 1.7 V, the Faradaic efficiency for formic acid production is as high as 94.1 % and the electro-to-chemical efficiency is 86.2 %.