Engineering defects in materials to tune their properties for different applications has gained momentum in recent years. Chemistry - An Asian Journal and ChemNanoMat, together with Prof. Shuangyin Wang (Hunan University, China), Prof. Qiang Zhang (Tsinghua University, China), Prof. Wei Zhang (Shaanxi Normal University, China), and Prof. Yi Jia (Griffith University, Australia) are greatly honored to assemble a special collection of the latest works on Defect Chemistry, directed mainly towards electrocatalysis, photocatalysis, and electrochemical energy storage.