Fuel Cell Geared in Reverse: Photocatalytic Hydrogen Production Using a TiO₂/Nafion/Pt Membrane Assembly with No Applied Bias

A polymer membrane electrode assembly (MEA) consisting of a TiO 2 photoanode, a Pt cathode, and a proton exchange membrane (PEM) was constructed to generate hydrogen continuously under UV excitation with no applied bias. The acidified methanol is oxidized at the UV-irradiated TiO 2 photocatalyst, and H + ions are driven to the Pt cathode surface through the Nafion membrane. Photocurrent generation of 0.34 mA/cm 2 under UV irradiation (λ > 300 nm) shows effective operation of the fuel cell in reverse for solar hydrogen production. A polarization curve of the photoelectrolysis cell exhibits an open circuit voltage of 0.5 V and a maximum power of 45 μW/cm 2 . The reduction of H + at a Pt cathode under no applied bias was confirmed from the evolution of H 2 gas with a rate of 69 μL h −1 cm −2 .