In-situ stabilizing surface oxygen vacancies of TiO2 nanowire array photoelectrode by N-doped carbon dots for enhanced photoelectrocatalytic activities under visible light

Oxygen vacancy was considered to act as electron scavengers, delaying electron-hole pair recombination for their critical impacts on the electronic-band structural modulation and optical absorption of a semiconductor. However, the generation and stabilization of oxygen vacancies (V-o) remains a considerable challenge. Herein, a N-doped carbon dots/V-o-rich TiO2 nanowire array (NCDs/TiO2 NA-V-o) photoelectrode with a stable oxygen vacancy layer in TiO2 energy band was constructed successfully by doping with NCDs. This optimized NCDs/TiO2 NA-V-o photoelectrode exhibited high activity and durability with a degradation reaction constant that was similar to two and three fold higher than that of TiO2 NA-V-o and TiO2 NA electrodes, respectively, and maintained a high degradation efficiency after eight consecutive degradation cycles. Moreover, the NCDs/TiO2 NA-V-o photoelectrode demonstrated a photocurrent density of 0.56 mA cm(-2), which was more than three times that of TiO2 NA electrode. These excellent visible light-driven photoelectrocatalysis (PEC) activities could be attributed to the stabilized and regulated oxygen vacancy layer induced by NCDs, which further accelerated the interfacial charge separation to generate more free radicals (e.g., (OH)-O-center dot, O-2(center dot-) and O-1(2)) confirmed by electron-spin resonance (ESR) and Photoluminescence Spectra (PL). Our work provides an effective strategy to regulate the defected TiO2 electrodes in the applications of visible light-driven wastewater treatment. (C) 2019 Elsevier Inc. All rights reserved.