Ch3oh Selective Oxidation To Hcho On Z-Scheme Fe2o3/G-C3n4 Hybrid: The Rate-Determining Step Of C-H Bond Scission

Fe2O3 as photoanode photoelectrocatalytic (PEC) CH3OH conversion is a promising approach for industrial preparation of high value-added HCHO. However, the conversion efficiency is limited by its poor charge separation and sluggish oxidation mechanism. This study reports a direct Z-scheme system consisting of 1D nanotubes oxygen-deficient alpha-Fe2O3 and g-C3N4 (ZOF@CN NTs) with great enhancement of PEC CH3OH oxidation to HCHO activity. The ZOF@CN NTs presents a CH3OH oxidation photocurrent density of 1.05 mA cm 2 at 0.6 V vs Ag/AgCl, 5.25 times than that of oxygen-deficient alpha-Fe2O3 alone (0.20 mA cm(-2)), and HCHO selectivity of 81.5%. Combining by UV-vis, UPS, PL spectroscopy, PEC performance and density functional theory calculations, the mechanism of CH3OH oxidation to HCHO on Z-scheme ZOF@CN NTs photoanode was found along following pathway: CH3OH*-CH3O*-CH2O*-CH2O (g), which is starting from the O-H bond scission and then followed by C H scission. The CH3O* via the C-H bond scission to form CH2O* is the key step for the reaction, and N atoms from g-C3N4 with higher electronegativity compared with O atoms, which is useful for C-H bond scission. This work serves as a solid foundation for understanding Fe2O3-based Z-scheme system photoanodes for CH3OH oxidation to HCHO.