Engineering graphitic carbon nitride (g-C3N4) for catalytic reduction of CO2 to fuels and chemicals: strategy and mechanism

Abstract

The reduction of carbon dioxide to useful fuels/chemicals, such as methane, formic, and methanol, is an innovative way to address looming energy and environmental issues. Graphitic carbon nitride (g-C₃N₄), as a greener and low-cost catalyst for the electrocatalytic and photocatalytic carbon dioxide reduction reaction (CO₂RR) to provide usable fuels, is endowed with numerous appealing attributes, e.g., Earth-abundant resources, facile synthesis, metal-free nature, catalytic properties, and unique thermal-physical–chemical stability. Articles on the use of g-C₃N₄ for CO₂ transformation have increased significantly in the past decade, and it is important to provide timely updates in this emerging and active research area. This review emphasizes the rational structural engineering of g-C₃N₄, including doping (i.e., metal, non-metal, and molecular) and heterojunction formation (i.e., metal, metal oxide, metal phosphide, metal hydroxide, metal complex, Ag-halides, and carbon materials) for electrocatalytic, photoelectrocatalytic, and photocatalytic CO₂RR. Besides, an in-depth deciphering of the CO₂RR mechanism from experimental, theoretical, and fundamental concepts is provided, including deliberation on the sources/emission and strategies to avoid/reduce CO₂ emission. Lastly, a brief conclusion and outlook on the challenges and future prospects are highlighted to assist further in the rational design of the g-C₃N₄-based catalyst as a selective and efficient catalyst for the CO₂RR.