Temperature Dependence of Reaction Kinetics in a Hybrid GaAs Solar-Fuel Cell Device.

The recently proposed single-electrode fuel cell (SEFC) is based on the chemovoltaic effect in a semiconductor p-n junction and as a hybrid device also allows operation as a photovoltaic cell. This study investigates the temperature dependence of the chemovoltaic effect in GaAs/GaInP p-n double heterojunction SEFC devices in the presence of both liquid and vapor methanol as a fuel. The experimental results reveal that increasing the temperature from room temperature to around 45 °C significantly enhances the fuel cell's performance by accelerating the electrochemical oxidation and reduction reactions injecting electrons and holes into the semiconductor bands. However, further increase in the fuel temperature, nearing the boiling point of methanol, leads to adverse effects on the cell's performance when submerged in the liquid fuel but still shows moderate improvement when operating with the vapor-phase fuel. These results provide insight into the kinetics of the chemovoltaic effect in a hybrid solar-fuel cell device.