Rational Modulation of Effective Mass Near Band Edge of Li₂SnO₃ to Increase Photogenerated Carrier Separation Ratio and Photocatalytic Performance

Photogenerated carrier separation is important in photocatalysis. Doping may offer control over the effective masses of the photogenerated electrons and holes. Herein, a doping strategy in Li₂SnO₃ enhanced photogenerated carrier separation, boosting photocatalysis. Substitution of Ge with Sn increased the effective mass of holes and reduced that of electrons; hence, the photogenerated electron/hole lifetime ratio in Li₂Sn_0.90Ge_0.10O₃ was approximately 2.8 times as great as that of Li₂SnO₃. Photocatalytic degradation by Li₂Sn_0.90Ge_0.10O₃ reached 100% within 12 min. However, the opposite effect was achieved upon doping with Pb. Theoretical calculations revealed that the low Ge-4p valence band orbital reduced hole mobility, while the Ge-4s orbital hybridized with O-2p near the conduction band minimum increased the electron mobility. Steady-state and time-resolved photoluminescence spectroscopy, electron spin resonance, and liquid chromatography–mass spectrometry were conducted to explore the photocatalytic mechanism. This study provides an understanding of structure–activity relationships to guide the design of high-performance photocatalysts.