Precise Lattice‐Strain Modulation of Hematite Enabled by Gradient Doping of Mn for Enhanced Photoelectrocatalytic Oxidative C─C Bond Scission

The high‐value utilization of biomass feedstock is fascinating but limited by efficient C─H activation to break C─C bonds. Herein, F‐Fe2O3‐Mn photoanodes with modulable compressive strain are fabricated by gradient infusion of Mn into F‐doped hematite (F‐Fe2O3), which is illustrated to be highly efficient for oxidative C─C bond cleavage of various bio‐based 1,2‐diols to produce benzoic acids or aromatic ketones (94.5–97.2% yields) in photoelectrocatalytic (PEC) device, coupling with a high H2 production of 1180 μmol cm−2 (≈96% yield). The gradient doping of Mn species into the photoelectrode bulk results in improved photoexcited carriers separation and transfer efficiency of the photoelectrode (3.41 mA cm−2). On the other hand, the lattice distortion induced by Mn doping also leads to a strain effect on F─Fe2O3─Mn, which can precisely modulate the photoelectrode electronic structure. Control experiments, in situ characterization, and theoretical calculations elaborate that compressive strain is capable of adjusting the position of the d‐band center to facilitate C─H activation, remarkably enabling PEC oxidative C─C bond breaking of 1,2‐diol and the desorption of the oxidized product. This “one‐stone‐two‐bird” strategy presents a straightforward protocol for efficiently breaking C─C bonds in organic and biomass transformations via PEC oxidation. Gradient doping of Mn can improve photoexcited carriers separation/transfer efficiency and modulate lattice strain on the photoelectrode to adjust its d‐band center position for enhanced C─H bond activation and C─C bond breaking activity. High‐efficiency oxidative upgrading of bio‐based 1,2‐diols to benzoic acids or ketones (94.5–97.2% yields) is achieved in a photoelectrocatalytic device, coupling with high H2 evolution (1180 μmol cm−2).