Construction of Heterostructured Sn/TiO2/Si Photocathode for Efficient Photoelectrochemical CO2 Reduction

Graphical CO 2 to formic acid : A novel kind of Sn/TiO 2 /Si photocathode is developed for CO 2 reduction reaction (CO 2 RR), which shows excellent selectivity to HCOOH under applied potential. The improved light performance and heterojunction composite structure, together with the modulated electronic configuration, co-contribute to the high CO 2 RR performance. Using renewable energy to convert CO 2 into liquid products, as a sustainable way to produce fuels and chemicals, has attracted intense attention. Herein, a novel heterostructured photocathode composed of Si wafer, TiO 2 layer, and Sn metal particles has been successfully fabricated by combining of a facile hydrothermal and electrodeposition method. The obtained Sn/TiO 2 /Si photocathode shows enhanced light absorption performance by the surface plasmon resonance effect of Sn metal. Especially, the Sn/TiO 2 /Si photocathode together with rich oxygen vacancy defects jointly promote photoelectrochemical CO 2 reduction, harvesting a high faradaic efficiency of HCOOH and a desirable average current density (−4.72 mA cm −2 ) at −1.0 V vs. reversible hydrogen electrode. Significantly, the photocathode Sn/TiO 2 /Si also shows good stability due to the design of protecting layer TiO 2 . This study provides a facile strategy of constructing an efficient photocathode to improve the light absorption performance and the electron transfer efficiency, exhibiting great potential in the CO 2 reduction.