Mutually supportive growth strategy to engineer a hollow biochar sphere-supported TiO2 composite with improved interfacial compatibility for efficient visible light-driven photocatalysis

Improving the interfacial compatibility between active components and support is significant and challenging. Herein, a mutually supportive growth strategy was created to engineer a Fe-Cu-doped hollow biochar sphere (HBS)-supported TiO2 (TiO2/Fe-Cu-HBS) composite with strong interfacial interaction via simultaneous growth of crystalline TiO2 and epitaxial carbonization of mechanical activation-treated starch-FeCl3-CuCl2. The TiO2/Fe-Cu-HBS composite with highly dispersed distribution and embedding of spherical TiO2 particles on the Fe-Cu-HBS shell had a narrow bandgap, favorable visible light capture and absorption capability, high separation efficiency of electron–hole pairs, and high transfer efficiency of photogenerated carriers. The superior photogenerated electron transport, high specific surface area, and enriched surface oxygen vacancies led to the generation of abundant reactive radicals on TiO2/Fe-Cu-HBS under visible light stimulation, contributing to efficient photocatalytic degradation of tetracycline hydrochloride (removal rate of 95.4% within 120 min; mineralization rate of 75.3% within 180 min), rhodamine B (removal rate of 99.2% within 100 min), and carbamazepine (removal rate of 67.5% within 120 min). Moreover, TiO2/Fe-Cu-HBS maintained high photocatalytic degradation efficiency after five cycles ascribed to its favorable structural stability. A mechanism of photocatalytic degradation of tetracycline hydrochloride and possible degradation pathways were proposed. This work provides a new growth strategy for constructing highly active and stable visible light-driven TiO2-based composite photocatalysts for effectively treating organic pollutants.