Hierarchical SnS₂/CuInS₂ Nanosheet Heterostructure Films Decorated with C₆₀ for Remarkable Photoelectrochemical Water Splitting

Abstract

Rational architectural design and catalyst components are beneficial to improve the photoelectrochemical (PEC) performance. Herein, hierarchical SnS₂/CuInS₂ nanosheet heterostructure porous films were fabricated and decorated with C₆₀ to form photocathodes for PEC water reduction. Large-size CuInS₂ nanosheet films were first grown on transparent conducting glass to form substrate films. Then, small-size SnS₂ nanosheets were epitaxially grown on both sides of the CuInS₂ nanosheets to form uniform hierarchical porous laminar films. The addition of C₆₀ on the surface of the SnS₂/CuInS₂ porous nanosheets effectively increased visible light absorption of the composite photocathode. Photoluminescence spectroscopy and impedance spectroscopy analyses indicated that the formation of a SnS₂/CuInS₂ heterojunction and decoration of C₆₀ significantly increased the photocurrent density by promoting the electron-hole separation and decreasing the resistance to the transport of charge carriers. The hierarchical SnS₂/CuInS₂ nanosheet heterostructure porous films containing multiscale nanosheets and pore configurations can enlarge the surface area and enhance visible light utilization. These beneficial factors make the optimized C₆₀-decorated SnS₂/CuInS₂ photocathode exhibit much higher photocathodic current (4.51 mA cm^-2 at applied potential -0.45 V vs reversible hydrogen electrode ) and stability than the individual CuInS₂ (2.58 mA cm^-2) and SnS₂ (1.92 mA cm^-2) nanosheet film photocathodes. This study not only reveals the promise of C₆₀-decorated hierarchical SnS₂/CuInS₂ nanosheet heterostructure porous film photocathodes for efficient solar energy harvesting and conversion but also provides rational guidelines in designing high-efficiency photoelectrodes from earth-abundant and low-cost materials allowing widely practical applications.