Photoelectrocatalytic reduction of CO2 into formic acid using WO3–x/TiO2 film as novel photoanode

A novel WO 3– x /TiO 2 film as photoanode was synthesized for photoelectrocatalytic (PEC) reduction of CO 2 into formic acid (HCOOH). The films prepared by doctor blade method were characterized with X-ray diffractometer (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The existence of oxygen vacancies in the WO 3– x was confirmed with an X-ray photoelectron spectroscopy (XPS), and the accurate oxygen index was determined by a modified potentiometric titrimetry method. After 3 h of photoelectrocatalytic reduction, the formic acid yield of the WO 3– x /TiO 2 film is 872 nmol/cm 2 , which is 1.83 times that of the WO 3 /TiO 2 film. The results of PEC performance demonstrate that the introduction of WO 3– x nanoparticles can improve the charge transfer performance so as to enhance the performance of PEC reduction of CO 2 into formic acid.