Recycling of spent alkaline Zn-Mn batteries directly: Combination with TiO2 to construct a novel Z-scheme photocatalytic system

[Display omitted] •A new approach was developed to recycling unpurified spent alkaline Zn − Mn batteries.•A novel Z − scheme TiO2@S − AZMB photocatalyst was synthesized.•The photocatalytic activity of degradation toluene by TiO2@S − AZMB was studied.•The enhancement mechanism of Z − scheme system on photocatalytic performance was explored. Recycling of spent alkaline Zn-Mn batteries (S-AZMB) has always been a focus of attention in environmental and energy fields. However, the current research mostly concentrated in the recovery of purified materials, and ignores the direct reuse of S-AZMB. Herein, we propose a new concept for the first time that unpurified S-AZMB can be used as raw materials for preparation of Z-scheme photocatalytic system in combination with TiO2. A series of characterizations and experiments confirm that the combination with S-AZMB not only extends the response of TiO2 to visible light, but also significantly enhances the separation ability of photogenerated electron-hole pairs. In the toluene removal experiment, the degradation kinetic rate of Z-scheme TiO2@S-AZMB photocatalyst reaches 21.0 and 10.5 times than that of TiO2 and S-AZMB, respectively. More notably, this S-AZMB based Z-scheme photocatalyst can maintain structural and photocatalytic performance stability in cyclic catalytic reactions. We believe that this work not only expands the research concept of recycling S-AZMB, but also provides a new idea for designing highly efficient Z-scheme photocatalysts.