Efficient Photoelectrocatalytic Reduction of CO2 to Selectively Produce Ethanol Using FeS2/TiO2 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.