Organic heterojunctions synergize with biochar as catalytic sites for rapid herbicide degradation under natural light

With the increasing pollution of water bodies by herbicides, there is an urgent need to develop an efficient and environmentally friendly photocatalyst using natural light. In this work, we combine the organic heterojunction PBDB-T:BTTIC-TT with biochar to design a low-cost photocatalyst-adsorbent with a higher density of reaction site and reduce the aggregation of the organic catalysts. By tuning the thiophene side chains of the acceptor in organic heterojunction, the visible-light absorption can be enhanced ∼18% for better catalytic efficiency. The ·O2− is verified to play a major role during the photocatalytic process, and the degradation pathway of 2,4,6-trichlorophenol to small carboxylic acids is also revealed. The broader natural light response with the good adsorption of the photocatalyst can effectively enhance the 2,4,6-trichlorophenol removal rate up to 97.4% within 1 h, and the excellent adaptability over a wide pH range as well as the great stability during 15 catalytic cycles shows the practical applications in the treatment of water bodies with different levels of herbicide pollution.