N-doped carbon dots@layer facilitated heterostructure of TiO2 polymorphs for efficient photoelectrochemical water oxidation

Abstract

Abstract A cocktail strategy was developed to fabricate sandwich nanostructure of hydrogenated C-doped anatase TiO2 nanocrystals/N-doped carbon dots@layer/rutile TiO2 nanorod array as an efficient photocatalyst for photoelectrochemical water oxidation. The one-dimensional, single crystalline nature of the innermost rutile TiO2 nanorod facilitates charge transport. The middle N-doped carbon dots@layer offers dual functionalities, with the N-doped carbon dots as the photosensitizer to harvest long wavelength lights and the N-doped carbon layer as the conductive layer for fast charge transport toward the current collector. The outermost hydrogenated C-doped anatase TiO2 nanocrystals serve to increase the visible light absorption and to form a type II heterostructure with the innermost rutile TiO2 nanorods to enahnce the charge separation. An enhancement of 86% in photocurrent density was achieved at 1.23 V (vs. RHE) under illumination of simulated sun light of 100 mW/cm2 by the sandwich nanostrcuture, as compared to that of the plain rutile TiO2 nanorod array. The enhancement was boosted to 228% under visible simulated sun light (λ > 400 nm) illumination. The photoconversion efficiency and photocurrent density retention rate were significantly improved from 0.23% and 60% for the plain rutile TiO2 nanorod array to 0.65% and 84% for the sandwich nanostructure, respectively.