Dynamic Oxygen Vacancy Formation via Photoexcitation in Sn-Modified Defective BiOCl Nanoflowers for Enhanced Photocatalytic Nitrogen Fixation
Dongrui Hou, Li Han, Ziyue Hou, Zirui Yang, Tianliang Lu, Xiaoqin Si, Xin liu, Jinrong Li, Wenbo Luo, Jianfeng Wang
Abstract
Oxygen vacancies (OVs) play a crucial role in photocatalytic nitrogen fixation, yet current studies predominantly focus on preconstructed OVs (PC-OVs), with limited attention given to photoexcitation-induced OVs (PE-OVs). In this work, Sn-doped BiOCl-V O (Sn-BOC-V O ) was synthesized via a facile one-pot hydrothermal method to actively generate PE-OVs. EPR analysis confirmed that Sn doping promotes the formation of PE-OVs. Quasi in situ XPS revealed that light irradiation further enhances OVs generation in Sn-BOC-V O and induces electron transfer from the O and Bi to the Sn. Photoelectrochemical tests demonstrated that Sn-BOC-V O improves visible-light absorption, facilitates charge separation, and suppresses carrier recombination, collectively leading to a 16.8-fold increase in the nitrogen fixation rate compared to BOC-V O . In situ DRIFTS spectroscopy tracked key reaction intermediates, while DFT calculations indicated electron transfer from Sn-BOC-V O to adsorbed N 2, highlighting the synergy between Sn and OVs in promoting N 2 activation and improving the photocatalytic nitrogen reduction reaction (pNRR) efficiency. Importantly, Sn-BOC-V O exhibits a reduced energy barrier of 1.81 eV for the rate-determining step, which is significantly lower than that of BOC-V O (2.22 eV), underscoring the critical role of Sn in optimizing reaction kinetics. This study offers insights into the design of photoexcited OV-active sites and emphasizes the dynamic role of OVs in catalytic reactions.