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

Rational architectural design and catalyst components are beneficial to improve the photoelectrochemical (PEC) performance. Herein, hierarchical SnS 2 /CuInS 2 nanosheet heterostructure porous films were fabricated and decorated with C 60 to form photocathodes for PEC water reduction. Large-size CuInS 2 nanosheet films were first grown on transparent conducting glass to form substrate films. Then, small-size SnS 2 nanosheets were epitaxially grown on both sides of the CuInS 2 nanosheets to form uniform hierarchical porous laminar films. The addition of C 60 on the surface of the SnS 2 /CuInS 2 porous nanosheets effectively increased visible light absorption of the composite photocathode. Photoluminescence spectroscopy and impedance spectroscopy analyses indicated that the formation of a SnS 2 /CuInS 2 heterojunction and decoration of C 60 significantly increased the photocurrent density by promoting the electron–hole separation and decreasing the resistance to the transport of charge carriers. The hierarchical SnS 2 /CuInS 2 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 C 60 -decorated SnS 2 /CuInS 2 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 CuInS 2 (2.58 mA cm –2 ) and SnS 2 (1.92 mA cm –2 ) nanosheet film photocathodes. This study not only reveals the promise of C 60 -decorated hierarchical SnS 2 /CuInS 2 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.