Understanding Self-Photorechargeability of WO3 for H2 Generation without Light Illumination

This work presents insight into the self-photorechargeability of WO3, whereby the intercalation of positive alkali cations is accompanied by the simultaneous storage of photo-excited electrons. The cyclic voltammetry studies verify the photo-assisted intercalation and de-intercalation of Na+ and K+ from the flower structured WO3. A storage capacity of up to 0.722 Ccm(-2) can be achieved in a saturated (0.68M) K2SO4 electrolyte solution. However, the best photo recharge-discharge stability of the electrode are observed at a lower (0.1 M) cation concentration. At high electrolyte concentrations, the intercalated cations are firmly trapped, as indicated by the structural modifications observed in Raman analysis, resulting in much less photocharging and discharging abilities in subsequent cycles. The study also shows that the stored electrons can be successfully used to generate H-2 with 100% faradaic efficiency in the absence of light.