Construction of biochar-modified TiO2 anatase-rutile phase S-scheme heterojunction for enhanced performance of photocatalytic degradation and photocatalytic hydrogen evolution

Abstract

Constructing step-scheme (S-scheme) heterojunction photocatalysts with high charge migration efficiency could enhance photocatalytic performance. In this study, biochar(BC)-modified TiO2 anatase(A)-rutile(R) phase S-scheme heterojunction photocatalysts was prepared through pyrolysis and hydrothermal methods. Results from various characterization techniques indicated a substantial improvement in the photocatalytic performance of BC/A/R-TiO2(550) under optimized conditions. This enhancement was attributed to the construction of a biochar-modified TiO2 anatase-rutile phase S-scheme heterojunction, which promoted the transfer of photogenerated carriers through the anatase-rutile interface. Moreover, when the interface of BC/A/R-TiO2(550) was irradiated with simulated sunlight, the built-in electric field, band edge bending, and coulomb force synergistically promoted the recombination of oxidized photogenerated electrons with reduced photogenerated holes while inhibiting the transfer of oxidized photogenerated holes with reduced photogenerated electrons. This phenomenon resulted in the high redox ability of both electrons and holes. Furthermore, photocatalytic degradation experiments revealed that the BC/A/R-TiO2(550) photocatalyst exhibited excellent photocatalytic activity, surpassing pure TiO2 and BC. The photocatalytic degradation performance of tetracycline (TC), ciprofloxacin (CIP), and norfloxacin (NOR) using BC/A/R-TiO2(550) was particularly high. Within 6 h, BC/A/R-TiO2(550) generated a hydrogen evolution amount of 159.7 μmol·h−1, which was 11.5 times higher than that of pure TiO2 (13.9 μmol·h−1). Additionally, the photocatalyst demonstrated good cycling stability. Through a series of studies on BC/A/R-TiO2(550), a possible photocatalytic mechanism on the as-formed S-scheme heterojunctions was proposed. Developing these novel S-scheme heterojunction photocatalysts presents a promising strategy for solar-driven photocatalysis, particularly in resolving the problems related to organic environmental pollutants.