Defect engineering in metal sulfides for energy conversion and storage

Defect engineering is regarded as one of the efficient approaches to modulating the physical and chemical properties of materials for energy-related applications. Metal sulfides (MSs) have increasingly aroused research concerns in energy conversion and storage fields for their tunable electronic structure, semiconducting traits and outstanding redox reversibility. Therefore, introducing defects into MSs is considered to be a promising way to construct highly-efficient materials for energy conversion and storage. However, the reviews about the comprehensive applications of defective MSs for the above application are rare. Herein, this review first summarizes different types of defects, including vacancies, doping, edge/screw dislocation, grain/twin boundaries, lattice disorders and voids, and diverse synthetic strategies, such as thermal treatment, plasma etching, elemental doping, chemical reduction, and phase transformation in MSs. More importantly, we elaborately discuss the diversified applications of the defective MSs in photocatalytic H2 evolution, CO2 reduction, N2 fixation, pollutant degradation, electrocatalytic H2 evolution, O2 evolution, O2 reduction, CO2 reduction, N2 reduction, photoelectrochemical water splitting, metal-ion/air batteries, lithium-sulfur batteries and supercapacitors. Finally, the current challenges and future perspectives for precisely synthesizing defective MSs (either with diverse defects or multinary MSs) applied in interdisciplinary domains and their advanced characterization techniques are also proposed.