High-Efficiency g-C3N4 Based Photocatalysts for CO2 Reduction: Modification Methods

Photocatalysis is an effective means to solve the greenhouse effect caused by the large amount of carbon dioxide (CO2) emissions from fossil fuel consumption. Graphitic carbon nitride (g-C3N4) has the advantages of suitable band gap, easy preparation, low price, and good stability, making it a promising semiconductor photocatalyst. However, bulk g-C3N4 also has disadvantages such as low gas adsorption, low photocatalytic efficiency, narrow spectral response, and easy recombination of electron–hole pairs. The modification method based on g-C3N4 photocatalyst helps to improve the above-mentioned problems. This review summarizes the research progress in recent years from four aspects: morphology adjustment, co-catalysts, heterostructures and doping. Each aspect includes the pros and cons of different improvement methods, the comparison of theoretical calculations and experimental results, the application of different characterization methods, and the detailed listing of product yield and selectivity. Prior to this, there was an explanation of the basic theory of semiconductor photocatalytic CO2 reduction. Finally, the future challenges and development prospects are also briefly prospected.