Constructing nitrogen vacancy introduced g-C3N4 p-n homojunction for enhanced photocatalytic activity

p-n homojunction is an efficient structure for a photocatalyst to improve separation of photo-generated carriers, and finally promote its photocatalytic activity. In the present work, the nitrogen vacancies (NVs) have been introduced to the n-type graphitic carbon nitride (g-C3N4) via secondary calcination of bulk g-C3N4 under hydrogen atmosphere for the construction of g-C3N4 p-n homojunction. The NVs were confirmed to be formed in g-C3N4 by a series of characterizations, and the amount of NVs gradually increased with the extension of secondary calcination time. Furthermore, the "V-shaped" Mott-Schottky plots determined the conductivity type of construction was p-n type. The results of photoelectrochemical measurement demonstrate p-n homojunction separated and transferred photo-generated carriers much more efficiently than by-type g-C3N4. Therefore, significantly enhanced photocatalytic activity was obtained for p-n homojunctions g-C3N4. The degradation rate for rhodamine b by p-n homojunction g-C3N4 was about 8.3 times that by bulk g-C3N4. The variety and quantity of reactive radicals were significantly increased in the constructed p-n homojunction system. The successful synthesis of p-n homojunction by introducing NVs into g-C3N4 may be a useful technique for purifying wastewater containing organic pollutants.