Effects of operating temperature on photoelectrochemical performance of CuWO4 film photoanode

Abstract

Photoelectrochemical (PEC) water splitting is a kind of strategy to produce hydrogen by using renewable energy. Copper tungstate (CuWO4) with a suitable bandgap (∼2.3 eV) is a potential candidate, but its poor charge transfer ability limits the real performance. According to the fact that the real reaction temperature is different from the normal temperature (298 K) in the laboratory, the testing temperature was considered as a potential influence factor for the PEC performance of photoelectrodes. In this study, the effects of temperature on the PEC properties of CuWO4 photoanode were discussed from the viewpoint of charge transfer in the photoanode, specific conductance and pH of the electrolyte, and the reaction Gibbs free energy. An increasing photocurrent is achieved by increasing the testing temperature, which is from 0.11 mA/cm2 (1.23 V vs RHE) at 5 ℃ to 0.31 mA/cm2 at 70 ℃. A similar increasing trend was seen between the carrier concentration and photocurrent, indicating the main influence factors are considered as improved carrier concentration and accelerated charge transfer ability of semiconductors. At higher temperatures, the risk of collisions of electrons and holes increases, although this negative effect is smaller than the positive effect brought on by greater carrier densities, as indicated by the smaller rise in current density compared to that of carrier density at 60/70/80/90 °C. This research suggests that a real-world factor favoring PEC water splitting is an increase in temperature.