Photocatalysis and electrocatalysis are essential for achieving efficient photochemical and electrochemical conversion, which have been regarded as promising technologies to address ever-increasing environmental problems and energy crises. To date, transition metals and their derivatives (oxides, sulfides, nitrides, and selenides) as well as nonmetal nanocarbons (carbon nanotubes, graphene, and graphitic carbon nitride) have been found to be potential photocatalysts or electrocatalysts. Despite research efforts, the single-component catalysts still show relatively low catalytic activity, which is mainly impeded by its intrinsic electron structure and limited active sites.

In recent years, defect creation in nanostructured materials - which attracts a lot of research attention - has proved to be an effective approach to increase the active site, modulate the electron structure, and thus improve catalytic activity. However, the foundational understanding of defect creation characterization, especially the relationship between defect and enhanced catalytic activity, is inadequate.

The aim of this Special Issue is to extend the defect-related understanding by collating original research and review articles focusing on defect engineering in nanomaterials for photocatalysis and electrocatalysis.

Potential topics include but are not limited to the following:

• Methods creating (intrinsic and impurity) defects in nanomaterials
• Defect quality (type, concentration, and spatial distribution)
• Elaborately control of defects
• Characterization of defects
• Relationship between defects and photocatalytic activity
• Relationship between defects and electrocatalytic activity