Photoassisted Oxygen Reduction Reaction in H₂ -O₂ Fuel Cells

The oxygen reduction reaction (ORR) is a key step in H₂ -O₂ fuel cells, which, however, suffers from slow kinetics even for state-of-the-art catalysts. In this work, by making use of photocatalysis, the ORR was significantly accelerated with a polymer semiconductor (polyterthiophene). The onset potential underwent a positive shift from 0.66 to 1.34 V, and the current was enhanced by a factor of 44 at 0.6 V. The improvement was further confirmed in a proof-of-concept light-driven H₂ -O₂ fuel cell, in which the open circuit voltage (V_oc ) increased from 0.64 to 1.18 V, and the short circuit current (J_sc ) was doubled. This novel tandem structure combining a polymer solar cell and a fuel cell enables the simultaneous utilization of photo- and electrochemical energy, showing promising potential for applications in energy conversion and storage.