Surface modifications of nanostructured thin films of copper sulphide: a novel approach to improve hydrogen gas generation and carbon dioxide reduction

Abstract

The use of fossil fuels for energy purposes releases substantial amount of pollutant gases into the atmosphere, such as carbon dioxide, which could result in a number of serious implications for the environment. In the light of these issues, urgent strategies need to be established to exploit new sources of energy, which must be abundant, renewable, sustainable, and resulting in minimised environmental impact. Regarding such requirements, the sun stands as a great candidate because it is the most abundant and clean natural source of energy. In addition, solar energy is versatile since it can be used in different manners, such as to produce chemical energy, that is, fuels, in photoelectrochemical cells. Such approach can be explored for the generation of hydrogen gas, which stands out as a clean and sustainable fuel, via photoelectrochemial water splitting, or even for the generation of methanol, ethanol, etc., via carbon dioxide reduction. Several semiconductor materials are under investigation to drive such reactions in photoelectrochemical cells. A particular class of semiconductors named as sulphur-based chalcogenides, e.g., copper sulphide, is gaining notable attention for being green and having fine optoelectronic properties for application in photoelectrochemical cells. In this context, herein we propose to obtain nanostructured thin films of copper sulphide by electrodeposition and to study their (photo)electrocatalytic properties for the generation of hydrogen gas via (photo)electrolysis of water and other fuels via (photo)electroreduction of carbon dioxide. Aiming to improve the photoelectrochemical performance of these reactions, it is also proposed to obtain the copper sulphide/protective layer/cocatalyst system. The protective layer will consist of titanium(IV) oxide, whilst the cocatalyst will be molybdenum sulphide. The physical and chemical properties of the copper sulphide films before and after surface modifications will be thoroughly characterised by means of X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The optoelectronic properties will be assessed by ultraviolet-visible-near infrared spectroscopy, (photo)electrochemical experiments, electrochemical impedance spectroscopy, and Mott-Schottky analysis. (AU)