Improved purification efficiency and stability of photocatalytic cement-based pavement coated with colloidal graphitic carbon nitride

Abstract

Photocatalytic coatings applied onto cement-based pavement materials have been intensely developed to purify runoff pollution and vehicle exhaust. However, the masking effect of the adhesive incorporation often results in an unsatisfactory purification efficiency. Thus, developing an adhesive-free photocatalytic coating with high stability and purification efficiency on cement-based pavements is still urgently needed. Herein, a colloidal graphitic carbon nitride (g-C3N4) modified with hydroxyl groups was sprayed onto cement pastes to prepare a photocatalytic coating on the cement-based materials. The results of photocatalytic degradation of Rhodamine B (RhB) indicated that the RhB degradation efficiency and stability of the colloidal g-C3N4-coated cement paste were significantly improved compared to pristine g-C3N4-coated cement paste. After a runoff-washing trial, photocatalytic RhB degradation by colloidal g-C3N4-coated cement paste was 13.8-fold higher than that of pristine g-C3N4-coated cement paste. Mechanistic studies suggested that the well-distributed membrane microstructure of colloidal g-C3N4 and coordinate bonds between colloidal g-C3N4 and calcium-silicate-hydrates were mainly responsible for the improved stability and purification efficiency of colloidal g-C3N4-coated cement pastes. These results support the use of colloidal g-C3N4 as a promising strategy to prepare photocatalytic cement-based pavements with good stability and purification efficiency.