High-Density Two-Dimensional SnS2 Nanoflake Array on Carbon Paper for Effective Photoelectrochemical Water Splitting

Abstract

Photoelectrochemical water splitting is a promising strategy to harvest energy from the sun; it utilizes a photoactive material, coupled with a slight electrical input, to convert water into hydrogen and oxygen. These generated gases are stored as chemical energy and can later be used as fuels. Among many reported photoactive materials, tin disulfide (SnS2) offers unique advantages due to the earth abundance of tin and its appropriate bandgap. Here, we report the fabrication of high-density two-dimensional vertically aligned SnS2 nanoflakes anchored on a conductive substrate for photoelectrochemical water splitting application. The as-fabricated nanoflakes were carefully studied, where crystalline, hexagonal SnS2 flakes can clearly be observed; their crystal structure has been indexed with the assistance of high-resolution transmission electron microscopy. For photoelectrochemical testing, a Solartron potentiostat was used to perform the indicative electrochemistry tests, including linear polarization, electrochemical impedance spectroscopy, and potential static with a light on–off current. A Horiba Hal-320 solar simulator was used as a light source to illuminate the active samples placed in a 0.5 M Na3PO4 aqueous electrolyte. The incident photon to converted electron figure was also calculated and was found to have 2.66% efficiency at zero bias (i.e., spontaneous evolution reaction) and 20.53% efficiency at 1 V bias. This high efficiency is probably due to both the high optical gap of ∼2.4 eV obtained from these 2D nanostructures and their physical structure that maximizes light trapping of the incident source.