Enhanced degradation toward Levofloxacin under visible light with S-scheme heterojunction In2O3/Ag2CO3: Internal electric field, DFT calculation and degradation mechanism

Abstract

• A novel S-scheme heterojunction In 2 O 3 /Ag 2 CO 3 composite was successfully synthesized. • The degradation rate reaches 86.1% of Levofloxacin during 90 min under visible light. • Heterojunction In 2 O 3 /Ag 2 CO 3 accelerates the separation of photogenerated carriers. • Reaction mechanism, intermediate product and electron transfer pathway are discussed. As we know, constructing a heterojunction with two semiconductors by matching energy bands can greatly promote photocatalytic performance. For this reason, a novel S-scheme heterojunction of In 2 O 3 /Ag 2 CO 3 was synthesized with in-situ hydrothermal precipitation methods. The characteristics and DFT calculation prove that the transfer of photogenerated electrons in the In 2 O 3 /Ag 2 CO 3 system follows the mechanism of S-scheme heterojunction. And the internal electric field (IEF) resulted from the S-scheme heterojunction of In 2 O 3 /Ag 2 CO 3 drives the direct transferring of photogenerated electrons from the conduction band of Ag 2 CO 3 to valence band of In 2 O 3 , resulting in an efficient separation of photogenerated electron-hole pairs and great accumulation of e – and h + on the CB of In 2 O 3 and VB of Ag 2 CO 3 , respectively. The photoluminescence lifetime of In 2 O 3 /Ag 2 CO 3 is greatly extended to 8.42 ns, and holes and hydroxyl radicals are the most important active radicals. As-prepared S-scheme heterojunction of In 2 O 3 /Ag 2 CO 3 shows the highest photodegradation rate (86.1%) and mineralization ability (46.2%) toward Levofloxacin under visible light. Finally, both probable degradation pathway and mechanism were presented. This work suggests a feasible method to construct a S-scheme heterojunction to optimize the redox ability of photocatalyst and promote the photocatalytic degradation capability toward harmful pollutants under visible light.