Herein, the FeS2/TiO2 p-n heterojunction was first utilized as a photoelectrode for the PEC reduction of CO2 to selectively produce ethanol. The FeS2/TiO2 photoelectrode was fabricated through electrochemical anodization, electrodeposition, and vulcanization methods. The impact of the FeS2 loading amount and applied bias on the PEC performance was investigated. The behavior of photocurrent polarity reverse is observed depending on the FeS2 loading amount, which is related to the energy band structure of the semiconductor/electrolyte interface. The active sites for ethanol production were identified on TiO2 nanotubes rather than on the FeS2 surface. Incorporation of FeS2 not only broadened the visible light absorption range but also formed a p-n heterojunction with TiO2. FeS2/TiO2 with an electrodeposition time of 15 min exhibits the highest ethanol yield of 1170 μmol L-1 cm-2 for 3.5 h of reaction under ultraviolet-visible (UV-Vis) illumination at an applied bias of -0.7 V. Compared to TiO2, FeS2/TiO2 showed significantly higher ethanol yield due to its appropriate loading amount of FeS2 and the synergistic effect of strong UV-Vis light absorption and efficient separation and transfer of charge carriers at the p-n junction.
Keywords: CO2 reduction; TiO2; ethanol; photoelectrocatalysis; p–n heterojunction.