The construction of lattice-matched CdS-Ag2S heterojunction photocatalysts: High-intensity built-in electric field effectively boosts bulk-charge separation efficiency

Abstract

The built-in electric field of heterojunction can effectively promote carrier separation and transfer. While, its interface orientation is often random, leading to lattice mismatch and high resistance, thus limiting the efficiency of interfacial charge transfer. Herein, the lattice-matched heterojunction (CdS-Ag2S) was constructed by ion-exchange epitaxial growth. The results of surface photovoltage spectroscopy (SPV), transient photovoltage spectroscopy (TPV), and time-resolved photoluminescence (TRPL) show that the lattice-matched heterojunction has higher charge separation efficiency and longer photogenerated carrier lifetime than that of lattice-mismatched one. The lattice-matched CdS-Ag2S has a high built-in electric field (BIEF) value of 103.42 and a bulk-charge separation (BCS) efficiency of 68.71%, which is about three times higher than that of the lattice-mismatched heterojunction (CdS-Ag2S-M). In addition, the photodegradation efficiency of CdS-Ag2S towards norfloxacin (NOR) was also 3.4 times higher than that of CdS-Ag2S-M. The above results and density functional theory (DFT) calculations indicate that improving the lattice matching at the heterojunction is beneficial for establishing a high-intensity built-in electric field and effectively promoting bulk-charge separation efficiency, thus achieving excellent photocatalytic performance. This work provides an essential reference for the research of high-performance heterojunction photocatalysts.