The CuS/SnS2 heterojunction with enhanced photo-assisted energy storage performances

Abstract

As a novel energy storage system, the combination of Pseudo-capacitance materials with photosensitive semiconductors to construct heterojunctions is regarded as a promising strategy for constructing advanced supercapacitors. For the design of composite materials, how to use heterojunctions to simultaneously achieve high capacitance and excellent photoreaction activity is of great significance. Although SnS₂ is a material that possesses two advantages simultaneously, there is no report on its enhancement behavior of photo-assisted capacitance, for the easy recombination with photogenerated charge carriers. Herein, a CuS/SnS₂ composite material supported on carbon cloth (CuS/SnS₂@CC) was fabricated using a two-step hydrothermal method and tested as a binder-free photo-electrode for photo-assisted electrochemical charge storage applications. The results showed that the construction of a CuS/SnS₂ p–n-type heterojunction greatly reduced the recombination efficiency of photogenerated electrons and holes. Consequently, the photo-assisted charging capacity of the electrode increased by 17.4%. The electrode also displayed a superior specific capacitance of 1043 mF cm⁻² at a current density of 0.5 mA cm⁻² in the dark and increased to 1155 mF cm⁻² under visible light illumination. Additionally, the electrode maintained a capacitance retention rate of 79.81% even at a high current density of 3 mA cm⁻². Meanwhile, the charge storage mechanism and band structure of CuS/SnS₂ were studied and discussed in detail. The proposed mechanism can also be expanded to other metal sulfide materials for better solar energy conversion and storage.