Efficient Photoelectrocatalytic Reduction of CO 2 to Selectively Produce Ethanol Using FeS 2 /TiO 2 p-n Heterojunction Photoelectrodes.

Herein, the FeS 2 /TiO 2 p-n heterojunction was first utilized as a photoelectrode for the PEC reduction of CO 2 to selectively produce ethanol. The FeS 2 /TiO 2 photoelectrode was fabricated through electrochemical anodization, electrodeposition, and vulcanization methods. The impact of the FeS 2 loading amount and applied bias on the PEC performance was investigated. The behavior of photocurrent polarity reverse is observed depending on the FeS 2 loading amount, which is related to the energy band structure of the semiconductor/electrolyte interface. The active sites for ethanol production were identified on TiO 2 nanotubes rather than on the FeS 2 surface. Incorporation of FeS 2 not only broadened the visible light absorption range but also formed a p-n heterojunction with TiO 2 . FeS 2 /TiO 2 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 TiO 2 , FeS 2 /TiO 2 showed significantly higher ethanol yield due to its appropriate loading amount of FeS 2 and the synergistic effect of strong UV-Vis light absorption and efficient separation and transfer of charge carriers at the p-n junction.