Water-Resistance-Based S-Scheme Heterojunction for Deep Mineralization of Toluene.

Deep mineralization of low concentration toluene (C 7 H 8 ) is one of the most significant but challenging reactions in photocatalysis. It is generally assumed that hydroxyl radicals (⋅OH) as the main reactive species contribute to the enhanced photoactivity, however, it remains ambiguous at this stage. Herein, a S-scheme ZnSn(OH) 6 -based heterojunction with AlOOH as water resistant surface layer is in situ designed for tuning the free radical species and achieving deep mineralization of C 7 H 8 . By employing a combination of in situ DRIFTS and materials characterization techniques, we discover that the dominant intermediates such as benzaldehyde and benzoic acid instead of toxic phenols are formed under the action of holes (h + ) and superoxide radicals (⋅O 2 - ). These dominant intermediates turn out to greatly decrease the ring-opening reaction barrier. This study offers new possibilities for rationally tailoring the active species and thus directionally producing dominant intermediates via designing water resistant surface layer.