Anion-Intercalation-Induced Symmetry Breaking in Layered BiOIO3 Boosts Macroscopic Polarization toward High-Performance Photoelectrochemical Iodide Ion Sensing.

The development of innovative photoelectrochemical (PEC) sensing strategies with exceptional selectivity and operational efficiency holds paramount strategic importance for advancing the frontiers of PEC technology. In this work, we present a novel congruent intercalation-induced symmetry breaking strategy to construct a highly selective PEC analysis platform. The near-perfect dimensional match between the ionic diameter of iodide (I-, 4.40 Å) and the interlayer spacing of BiOIO3 (4.41 Å) enables selective intercalation of I- while effectively excluding analogous halide ions (Br-, Cl-, and F-). This unique intercalation process induces charge distribution symmetry breaking around the IO3 motifs, resulting in a remarkable enhancement of the macroscopic polarization electric field in BiOIO3 and consequently amplifying photocurrent generation. The proposed system achieves ultrasensitive I- detection with an outstanding detection limit of 0.06 μM (S/N = 3), while maintaining exceptional selectivity. Furthermore, the PEC assay demonstrates superior operational efficiency, featuring a simplified workflow and rapid response time (3 min). This study offers a promising approach to induce symmetry breaking through spontaneous intercalation of exogenous species, circumventing the harsh high-temperature/pressure conditions typically required for chemical bond cleavage in conventional doping methods. The proposed strategy offers distinct advantages, including low energy consumption, mild operational conditions, and fast kinetics. More significantly, the introduction of symmetry breaking opens a new avenue for exploration of PEC sensing mechanisms, demonstrating broad application prospects and considerable potential for future development in advanced PEC systems.