Synergistic Effect of Photochromism and Vacancy Engineering within Z‐Scheme Doped BiOBr‐BaTiO ₃ Heterostructures Promoting CO ₂ Photocatalysis

Abstract Realizing solar‐driven CO ₂ conversion into high ‐ value fuels in pure water using non ‐ noble metal photocatalysts without sacrificial agents is challenging, with low conversion efficiency due to poor charge transfer and catalyst deactivation. Herein, a novel strategy is proposed by synergizing the vacancy engineering and photochromic effect enabling the enhanced photocatalytic CO ₂ reduction performance. Through the above strategy, BaTiO ₃ /Cl, I co‐doped BiOBr (BTO‐BCBI) Z‐Scheme heterojunctions are developed, which achieve pre‐catalytic attributes via water and UV irradiation, enabling excellent light absorption, and carrier transfer. The BTO‐BCBI composite exhibits superior performances of CO ₂ conversion into CO with a selectivity of 94% and CO yield rate of 192.0 µmol g ⁻¹ under 6 h solar irradiation without sacrificial agents while maintains robustness after five cycles. The CO evolution rate for BTO‐BCBI is 4.2 times that of the Cl, I‐co‐doped BiOBr (BCBI) composite and 9.7 times that of BaTiO ₃ ‐BiOBr (BTO‐BB). Comprehensive spectroscopic characterizations disclose that the increased activity is attributed to the increased separation of charge carriers resulting from the construction of heterostructure and the synergistic effect of photochromic effect and vacancy engineering. This highlights the key value of such synergy of photochromism and vacancy engineering for heterojunction photocatalyst development.