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

Herein, the FeS/TiO p-n heterojunction was first utilized as a photoelectrode for the PEC reduction of CO to selectively produce ethanol. The FeS/TiO photoelectrode was fabricated through electrochemical anodization, electrodeposition, and vulcanization methods. The impact of the FeS loading amount and applied bias on the PEC performance was investigated. The behavior of photocurrent polarity reverse is observed depending on the FeS 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 nanotubes rather than on the FeS surface. Incorporation of FeS not only broadened the visible light absorption range but also formed a p-n heterojunction with TiO. FeS/TiO with an electrodeposition time of 15 min exhibits the highest ethanol yield of 1170 μmol L cm for 3.5 h of reaction under ultraviolet-visible (UV-Vis) illumination at an applied bias of -0.7 V. Compared to TiO, FeS/TiO showed significantly higher ethanol yield due to its appropriate loading amount of FeS and the synergistic effect of strong UV-Vis light absorption and efficient separation and transfer of charge carriers at the p-n junction.