Photo-thermal-piezo multi-field coupling accelerating spatial charge separation and surface reaction kinetics in S-scheme heterojunctions for efficient photocatalysis

The simultaneous optimization of light utilization, charge-carrier separation/transport, and surface reaction kinetics remains a challenge in the design of high-performance photocatalysts. Although S-scheme heterojunctions improve charge separation, their performance is often constrained by the limited built-in electric field and insufficient utilization of near-infrared (NIR) light: the former fails to effectively drive bulk charge separation, while the latter directly restricts the spectral range of the photoresponse. Herein, a photo–thermal–piezo multi-field coupling strategy based on an atomically shared Bi 3 O 4 Br:Er 3 + /Bi 19 S 27 Br 3 S-scheme heterojunction is developed. This architecture overcomes interfacial transport barriers typical of ternary systems and integrates the upconversion functionality of Er 3+ , the photothermal effect of Bi 19 S 27 Br 3 , intrinsic piezoelectric polarization, and an S‑scheme charge-transfer pathway. The system achieves broad-spectrum solar harvesting, enhanced spatial charge separation, and accelerated surface reaction kinetics, as validated by multiscale characterization and theoretical simulations. Under photo–thermal–piezo multi‑field conditions, the optimized Bi 3 O 4 Br:Er 3+ /Bi 19 S 27 Br 3 heterostructure achieves complete Cr(VI) reduction within 16 min, a 35.3-fold enhancement compared with the performance of Bi 3 O 4 Br:Er 3+ . Additionally, it delivers a CO yield of 410.1 μmol·g −1 ·h −1 . This work demonstrates that multi-field synergy can concurrently optimize the three fundamental steps of photocatalysis, providing a novel design paradigm and mechanistic insight for the development of advanced photocatalytic systems.