Abstract
The results of these studies were divided into three parts. The first part demonstrate that ZnO nanowire (NW) arrays were successfully fabricated via a hydrothermal method in two steps. Prolonging the calcination time of the seed layer makes the ZnO NWs improve the photo-electrochemical performance. The ZnO NWs array electrode prepared from the seed layer with calcination at 350oC for 5 h shows a maximum half-cell solar-to-hydrogen (HC-STH) efficiency of 0.26% was obtained at a relatively low potential bias (0.6 V vs. RHE). In addition, we use design of experiment (DOE) to optimize the seed layer condition. In the second part, the TiO2 deposited onto ZnO NWs were synthesized via a sol–gel method with the varied concentration of titanium precursor. This heterojunction structure enhanced photocurrent densities, reaching values of about 720 A cm-2 under 100 mW cm−2 simulated solar light, which is 130% folds better than the bare ZnO NWs. In the third part, we conduct the stability of ZnO NWs in varied electrolytes under the solar light and UV light. The photocurrent of ZnO photoanodes measured in the sodium sulfate electrolyte decayed rapidly, whereas ZnO photoanodes exhibited the long-term stability when tested in a borate buffer.