Enhanced Visible-Light-Driven Photoelectrochemical Activity in Nitrogen-Doped TiO<sub>2</sub>/Boron-Doped Diamond Heterojunction Electrodes
Jiangtao Huang, Aiyun Meng, Zongyan Zhang, Shaolei Xiao, Xuanmeng Guo, Xiao‐Yuan Wu, Shuqi Huang, Guanjie Ma, Peigang Han, Bin He
Abstract
Doping and constructing heterojunctions have been demonstrated to be effective for improving the catalytic activity of titanium dioxide (TiO2); however, better performance is still widely expected for practical applications in renewable energy, environmental issues, etc. TiO2/boron-doped diamond (BDD) heterojunction is a promising approach that has been extensively studied in recent years. Herein, nitrogen-doped TiO2 (N-TiO2)/BDD heterojunction is proposed by employing N-TiO2 instead of TiO2. The N-TiO2/BDD heterojunctions were fabricated and systematically characterized to make a detailed comparison between N-TiO2/BDD and TiO2/BDD. The photoelectrochemical (PEC) activity was tested under 1 sun and visible light irradiation, respectively. N-TiO2 showed stronger photoresponse with the extended absorption spectrum that covered both UV and visible ranges. Besides, N-TiO2 also showed higher electrical conductivity due to the higher carrier concentration introduced by N doping. Therefore, larger current density and more efficient charge transport were demonstrated in N-TiO2/BDD heterojunctions, achieving enhanced PEC activity. Interestingly, compared with that of TiO2/BDD, the PEC activity of N-TiO2/BDD was weak at a low applied bias potential (<1.6 VRHE), but it increased dramatically and became much stronger than that of TiO2/BDD at a higher potential (>2.1 VRHE). This was suggested to be caused by the higher carrier concentrations and variation of electronic structures in N-TiO2. The PEC activity could be further promoted if the bias potential was further improved, resulting in excellent PEC performance that could not be realized by TiO2/BDD. Moreover, the doping concentration of N-TiO2 exhibited complicated influences on the PEC performance and needed to be elaborately controlled. Based on the optimized conditions, the largest current density achieved was 0.51 mA/cm2 at 2.8 VRHE and 1 sun irradiation, which was 2.22 times that of TiO2/BDD (0.23 mA/cm2). The carrier transport mechanism was discussed based on the experimental results. The N-TiO2/BDD electrodes showed degradation efficiency 2 times that of tetracycline hydrochloride (TCH) compared with that of undoped TiO2/BDD, which demonstrated promising applications of N-TiO2/BDD in the treatment of organic pollutants.