ZnFe2O4/ ZnO 0D-1D heterojunction for efficient photoelectrochemical water splitting

Abstract

In this work, both ZnO nanorods (NRs) thin films and ZnO NRs powder were successfully synthesized by open aqueous solution bath technique. Further, the residual ZnO nanorods (NRs) powder was used to synthesize ZnFe2O4 (ZFO) nanoparticles (NPs) by hydrothermal method. Finally, ZFO/ZnO heterojunction thin films were prepared and tested for photoelectrochemical water splitting application. The ZFO loading was controlled and tuned by drop-casting various numbers of drops (10, 20, 30 and 40) on the ZnO NRs films keeping the area constant. An improved photocurrent density ∼0.82 mA/cm2 was observed for optimized 30 ZFO/ZnO NRs thin films as compared to ∼0.19 mA/cm2 for pristine ZnO NRs thin films at 1.23 V vs RHE under 100 mW/cm2 light in a 0.1 M Na2SO4 neutral electrolyte. This remarkable enhancement in photocurrent for 30 ZFO/ZnO heterojunction compared to pure ZnO NRs array is attributed to increased light absorption induced electron-hole pairs generation, effective charge transfer and better charge separation at the ZFO/ZnO interface due to a favorable band alignment. This was confirmed with the incident photon to current conversion efficiency (IPCE) measurements which exhibit a significantly high value (∼14%) for 30 ZFO/ZnO films than pristine ZFO and ZnO thin films. It is worthy to note that ZFO NPs coated ZnO thin films deliver long term stability of the electrode against photocorrosion.