Homojunction type of carbon nitride as a robust photo-catalyst for reduction conversion of CO2 in water vapor under visible light

Abstract The value-added conversion of CO2 by photocatalytic reduction is considered as a potential way to solve the current energy and environmental crisis. In this paper, we report that a mechanical mixture of the as-thermally polymerized melamine (Me)- and 3-amino-1,2,4-triazole (AT)-based nitride carbons (MCN and TCN) can turn into a homojunction material (MTCN) by a calcination under air. A series of characterizations and photo-catalytic tests, combined with DFT calculations, support that the constructed MTCN has an improved porosity and photoelectric conversion efficiency. And the nitrogen-rich structure not only broadens the visible light response range but also provides stronger Lewis basic sites for the adsorption and activation of CO2 at the surface. As a result, MTCN exhibits the most outstanding performance on tetracycline degradation under visible light illumination. In particular, its photo-catalytic efficiency for the visible-triggered CO2 reduction under normal temperature and pressure can reach 7.75 μmol·g−1·h−1, which is 13.8 or 16.1 times higher than the single MCN or TCN. This work provides a facile pathway to construct CN-based homojunction photocatalyst for the efficient conversion of CO2 into valuable products.