Mechanism of p-Type Heteroatom Doping of Lithium Stannate for the Photodegradation of 2,4-Dichlorophenol: Enhanced Hole Oxidative Capability and Concentrations

Abstract

A systematic evaluation of enhancing photocatalysis via aliovalent cation doping is conducted. Cation In 3+ , being p-type-doped, was chosen to substitute the Sn site (Sn 4+ ) in Li 2 SnO 3 , and the photodegradation of 2,4-dichlorophenol was applied as a model reaction. Specifically, Li 2 Sn 0.90 In 0.10 O 3 exhibited superior catalytic performance; the photodegradation efficiency reached about 100% within only 12 min. This efficiency is far greater than that of pure Li 2 SnO 3 under identical conditions. Density functional theory calculations reveal that introducing In 3+ increased the electron mobility, yet decreased the hole mobility, leading to photogenerated carrier separation. However, photoluminescence and time-resolved photoluminescence suggest that In 3+ induced nonradiative coupling in the matrix, reducing the photogenerated carrier separation ratio compared with that of Li 2 SnO 3 . The optical band gap of Li 2 Sn 0.90 In 0.10 O 3 was almost unchanged compared with that of Li 2 SnO 3 via ultraviolet−visible absorption. The increased photocatalytic efficiency was ascribed to the lower valence band position and enhanced hole concentrations by valence band X-ray photoelectron spectroscopy and electrochemical measurements. Finally, a 2,4-dichlorophenol degradation pathway, an intermediate toxicity assessment, and a photocatalytic mechanism were proposed. This work offers insights into designing and optimizing semiconductor photocatalysts with high performance.