Advances in the synthesis and functionalization of two-dimensional iron sulfides for energy applications: Advances in the synthesis: J. Lee, J. Yang

Abstract: Transition metal dichalcogenides (TMDs) composed of 4d or 5d elements exhibit intrinsic two-dimensional layered structures, whereas 3d transition metals typically form non-layered structures when combined with chalcogens, which have received relatively less attention. Recent studies have focused on synthesizing two-dimensional structures from inherently non-layered materials to exploit their enhanced surface activity and improved electrochemical performance. Iron sulfides have attracted attention due to their nature abundance, low environmental toxicity, and high stability, making them suitable for energy applications. FeS₂, in particular, has an appropriate band gap, high electrical conductivity, and high absorption coefficient, making it suitable for use in electronic devices and energy storage systems. Elucidating the methodologies for synthesizing two-dimensional iron sulfide structures is crucial for advancing their potential applications in these fields. This review aims to systematically present the synthesis strategies for two-dimensional structures of 3d transition metal chalcogenides, emphasizing iron sulfides. It also explains physicochemical properties such as electrical conductivity, surface activation, and structural stability when synthesized into two-dimensional structures and discusses their impact on energy-related applications. Highlights: This review explores the synthesis of two-dimensional iron sulfides and their promising applications in energy storage and conversion systems. The discussion highlights the importance of overcoming challenges related to material quality to enhance performance in various energy-related technologies. Discussion: Iron sulfides exhibit diverse physicochemical properties depending on their crystal structures, demonstrating significant potential for applications in energy storage and conversion systems. Particularly, two-dimensional iron sulfide structures have garnered attention as next-generation materials due to their amenability to surface modification and structural advantages suitable for various electronic device applications. However, systematic research on efficient synthesis methods and characterization of two-dimensional structures remains insufficient at present.