Synergistic effect of polyoxometalate solution and TiO2 under UV irradiation to catalyze formic acid degradation and their application in the fuel cell and hydrogen evolution

The synergistic effect of H3PMo12O40 or H3PW12O40 polyoxometalate solution (POM) and TiO2 to catalyze formic acid oxidation was investigated. Under UV irradiation, hole and electron were photogenerated by TiO2. Formic acid was oxided by the photogenerated hole and photogenerated electron was transferred to reduce polyoxometalate. With this design, formic acid can be converted into electricity in the fuel cell and hydrogen can be generated in the electrolysis cell without noble metal catalyst. Unlike other noble metal catalysts applied in the fuel cells and electrolysis cell, POM and TiO2 are stable and low cost. The maximum output power density of liquid formic acid fuel cell after 12 h UV irradiation is 5.21 mW/cm2 for phosphmolybdic acid and 22.81 mW/cm2 for phosphotungstic acid respectively. The applied potential for the hydrogen evolution is as low as 0.8 V for phosphmolybdic acid and 0.6 V for phosphotungstic acid. Keywords: TiO2, UV, Polyoxometalate solution (POM), Fuel cell, Hydrogen evolution