Photothermal catalytic degradation of volatile organic compounds (VOCs) has been deemed as a promising strategy for the air purification. In this work, LaMnO3/N-doped biochar (NBC) composites with rich oxygen defects and nitrogen-containing functional groups were successfully synthesized by co-pyrolysis of soybean dregs and Mn/La salts, and they were employed for photo-thermal catalytic decomposition of p-xylene. N atoms from soybean dregs were successfully embedded into the biochar framework by the La3+ and Mn2+ modification. The abundant nitrogen-containing functional groups promoted the adsorption and enrichment of p-xylene on the catalysts surface. The carbon doping from soybean dregs increased oxygen defects of LaMnO3, which acted as the active center for p-xylene degradation. The p-xylene degradation rate reached as high as 99.6 % for LaMnO3/NBC-1.5 composite, which was significantly higher than that of pristine LaMnO3 (65.2%). The biochar introduction enhanced the visible light absorption of LaMnO3/NBC composites and then converted them into thermal energy, serving as extra heat source for p-xylene degradation. Moreover, the photogenerated electron-hole pairs of LaMnO3/NBC composites further generated active radicals such as •OH and •O2− with strong oxidative properties on the catalysts surface, which participated and enhanced the oxidative degradation of p-xylene.

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