An efficient, formic acid selective CO2 electrolyzer with a boron-doped diamond cathode

We fabricated a CO2 electrolyzer in order to investigate the energy requirements and the electrical-to-chemical energy conversion efficiency obtained when using boron-doped diamond as the cathode. The main product in the electrochemical reduction of CO2 using a boron-doped diamond electrode is formic acid, with a faradaic efficiency of 96%. The electrical-to-chemical energy conversion efficiency was investigated at various bias voltages, and it reached 43%, very close to the predicted maximum value, at a cell voltage of 3 V. If the secondary products, hydrogen and carbon monoxide, are also considered, the total electrical-to-chemical energy conversion efficiency was as much as 45%.