Graphitic Carbon Nitride for Electrochemical Energy Conversion and Storage

Owing to the rising pressure on the requirement of commercializing sustainable and environmentally friendly energy technologies such as proton exchange membrane fuel cells (PEMFCs), metal–air batteries, and water splitting electrolyzers, it is urgent to develop highly efficient electrocatalysts to replace costly platinum group metals. Graphitic carbon nitrides (g-C3N4) have attracted intensive focus due to their unique properties and impressive performance in challenging the widely accepted nitrogen-doped carbon materials in electrocatalytic fields. However, the relatively poor conductivity limits further improvement of g-C3N4-based electrocatalysts. Thus, this Review is primarily focused on recent progress in the functionalization of g-C3N4 materials for oxygen reduction and water splitting reactions. Especially, an innovative and in-depth understanding of g-C3N4 materials is presented by systematically summarizing the function of g-C3N4 materials, such as serving as active sites, coordination complexes, and supporter/protective coatings, in contributing to the catalytic performance. Finally, the main challenges and future perspectives of g-C3N4-based nanomaterials in electrocatalytic fields are also discussed. It should be noted that in the text we acknowledge that "many" (in fact, most) of the g-C3N4 materials have been polymeric amorphous phases within the C–N–H system. To avoid debate and confusion on the naming of previously reported "graphitic carbon nitride" materials in our Review, we decided to call all these of materials "g-C3N4" in accordance with previous reports.