Enhancing photoactivity of defective g-C3N4 via self-polarization effect of tourmaline for CO2 reduction

Graphite carbon nitride (g-C3N4) has been extensively studied as a non-metallic catalyst for photocatalytic reduction of CO2. However, its efficiency and selectivity in CO2 reduction still require further enhancement. In this study, we have incorporated the silicate mineral tourmaline, known for its spontaneous polarization properties, into g-C3N4 with nitrogen defects. The novel composite catalyst, named TM/CN(NH), was synthesized by a two-step method of high-temperature calcination. The optimal composite ratio of the sample (25TM/CN(NH)) can achieve a CO yield rate of 118.17 μmol g-1 h-1, which is 6.4 times that of the bulk g-C3N4(CN) and 2.9 times that of g-C3N4 containing N defects (CN(NH)). Our findings indicate that the self-polarization effect of tourmaline and the introduction of nitrogen vacancies can remarkably upgrade the photocatalytic efficiency of g-C3N4. On one hand, the nitrogen vacancies can broaden the light absorption range of g-C3N4, optimize its band gap structure, and improve its efficiency in utilizing light energy. On the other hand, the electric field generated by the self-polarization effect of tourmaline can enhance the migration of electrons in the lattice of g-C3N4, promote the migration and separation of electrons and holes, and thus increase the reduction efficiency of CO2 by g-C3N4. This research innovatively integrates cost-effective mineral materials into g-C3N4, significantly elevating the photocatalytic capabilities of g-C3N4. Furthermore, it paves the way for the rational design of abundant and inexpensive catalysts, aiming to achieve efficient photocatalytic carbon dioxide reduction.