Stable NO purification over S-scheme Bi2O3/Bi4O5Br2 with dynamic oxygen defects: Interfacial electric field steering charge separation and molecular activation

The construction of cost-effective photocatalytic systems is crucial for industrial NOx purification. This study developed S-scheme Bi 2 O 3 /Bi 4 O 5 Br 2 heterojunctions, revealing the interfacial charge transfer mechanism through systematic characterization. Experimental results showed that when the molar ratio of Bi 2 O 3 to Bi 4 O 5 Br 2 was 5:1, the composites showed an excellent NO removal, with the initial concentration of 705.40 ppb decreased to 224.28 ppb under visible light, and the activity was attenuated only by 6.72% (NO removal efficiency from 65.83% to 59.11%) after five cycles, showing excellent stability. The combination results of density functional theory and experiments indicated that the interface electrons of the heterojunction tended to transfer from Bi 2 O 3 to Bi 4 O 5 Br 2 , forming a built-in electric field, which significantly improved the separation efficiency of the photogenerated electron-hole pairs. The S-scheme Bi 2 O 3 /Bi 4 O 5 Br 2 heterojunction combined with dynamic photo-induced oxygen defects could significantly enhance the O 2 and H 2 O adsorption activation, which was conducive to the reactions of photogenerated e − /h + with O 2 /H 2 O to generate •O 2 − /•OH under visible light, greatly improving NO oxidation removal efficiency. The oxidation reaction pathway of NO on the surface of Bi 2 O 3 /Bi 4 O 5 Br 2 heterojunctions was revealed by in situ DRIFTS (NO→NO 2 →NO 3 − ). This work establishes novel theoretical perspectives and experimental paradigms for designing highly efficient lattice-matched heterojunction photocatalysts. The S-scheme heterojunction constructed from Bi 2 O 3 /Bi 4 O 5 Br 2 exhibits a built-in electric field at its interface. Under visible light irradiation, the dynamics oxygen defects were formed, which could combine with this built-in electric field drove the directional migration of photogenerated electrons and holes, thereby facilitating the separation of photogenerated carriers. Simultaneously, H 2 O and O 2 molecules were effectively activated at the interface, which facilitated the conversion of photogenerated e − and h + into ·O 2 − and ·OH. and under the action of these free radicals, NO was gradually converted into intermediate products such as NO 2 , and ultimately oxidized to NO 3 − . • S-scheme Bi 2 O 3 /Bi 4 O 5 Br 2 removes 68.2 % NO with >93 % stability over 5 cycles. • Built-in electric field and dynamic oxygen defects synergistically accelerate charge separation/transport. • Promoting O 2 /H 2 O activation to generate abundant .•O 2 − /•OH radicals, selectively oxidizing NO to NO 3 − .