Hydrogen Production by Photoelectrochemically Splitting Solutions of Formic Acid

Abstract A TiO 2 /FTO (FTO=fluorine‐doped tin oxide) electrode was prepared by dip‐coating FTO in a suspension of TiO 2 prepared from a sol–gel method and was used as a photoanode to split an aqueous solution of formic acid to produce hydrogen. The surface of the TiO 2 /FTO film was covered with assemblies of TiO 2 nanoparticles with a diameter of approximately 20 nm. Under irradiation by using a Xe lamp, splitting of formic acid was performed at different applied current densities. Compared to splitting water or utilizing FTO and Pt foil as the anode, the splitting voltage is much lower and can be as low as −0.27 V. The results show that the splitting voltage is related to the concentration of free formate groups. The evolution rate of hydrogen measured by using gas chromatography is 130 μmol h −1 at a current density of 20 mA cm −2 and the energy‐conversion efficiency can be 1.79 %. Photoelectrolysis of formic acid has the potential to be an efficient way to produce hydrogen with a high energy‐conversion efficiency.