Interfacial charge redistribution in carbon nitride/bismuth-based heterostructures confined by inverse-opal silica

An electrically insulating inverse-opal silica scaffold was used to confine graphitic carbon nitride/bismuth-based oxide-oxyhalide heterostructures and to examine whether a nonconductive porous host can regulate local photocatalytic interfacial behavior without acting as a long-range electron-transport pathway. Kelvin probe force microscopy, irradiated X-ray photoelectron spectroscopy, time-resolved photoluminescence, electrochemical impedance spectroscopy, transient photocurrent measurements, electron paramagnetic resonance spin trapping, radical-scavenging tests, and adsorption-separated pollutant reactions were jointly evaluated. Upon illumination, the optimized confined heterostructure exhibited a surface-potential increase from approximately 520 ± 12 to 601 ± 17 mV and an apparent work-function decrease from 4.78 to 4.70 eV, while its average photoluminescence lifetime decreased from 1.71 to 1.51 ns. Despite attenuated electrode-collected photocurrent, enhanced local reactive-species signals and irradiation-stage transformation were observed. Ciprofloxacin removal reached approximately 88.15%, including 41.01% dark adsorption, whereas rhodamine B removal reached 99.54%, with 86.96% occurring during dark adsorption. These results demonstrate that long-range charge collection and local surface redox utilization can respond differently in confined particulate photocatalysts. The combined observations support, but do not uniquely prove, a dielectric-confinement-assisted interfacial model and provide a framework for designing nonconductive porous hosts for adsorption-assisted surface photoredox processes.