Abstract
A photoelectrochemical device was achieved by interfacial self-assembly of macrocyclic π-conjugated copper phthalocyanine (CuPc) on surface of TiO2 nanorod arrays (NRs). The photocurrent density of the elegant TiO2@CuPc NRs photoanode reaches 2.40 mA/cm2 at 1.23 V vs. RHE under the illumination of 100 mW/cm2 from AM 1.5G sun simulator, which is 2.4 times higher than that of the pure TiO2. At the same time, the photoelectrochemical device constructed through this strategy has good stability and the photocurrent density remain almost no decline after 8 h of continuous operation. The Mott-Schottky and LSV curves demonstrate that CuPc act as a co-catalyst for water oxidation and a possible mechanism is proposed for water oxidation based on careful analysis of the detailed results. The holes from VB of TiO2 photogenerated by electrons exciting are consumed by a process in which Cu2+ is oxidized to Cu3+ and Cu4+, and then oxidize water to produce oxygen. CuPc species is considered to be a fast redox mediator to reduce the activation energy of water oxidation in and effectively promote charge separation.
Highlights
Photoelectrochemical (PEC) water splitting is considered as one of the most promising technologies to address the challenges of impending worldwide energy consuming and associated climate change resulting from combustion of fossil fuels (Du and Eisenberg, 2012; Wang et al, 2016; Seh et al, 2017)
The results shown that: (1) the morphology of the electrode after operation is almost the same as that before operation (Figure S5); (2) X-ray photoelectron spectroscopy (XPS) measurement (Figures S11, S12) confirmed the exist of conjugated copper phthalocyanine (CuPc) on the sample after operation, but the Inductively coupled plasma (ICP) measurement show that the loaden amount of CuPc is declined compared to the sample before operation
In order to further understand the enhanced PEC performance, the inherent electronic properties of CuPc assembled TiO2 nanorod arrays (CTNRAs) were characterized by measuring electrochemical impedance spectroscopy (EIS), the onset OER potential and linear Tafel plots
Summary
TiO2 nanorod arrays (Akira and Kenichi, 1972; Liu L. et al, 2013; Li et al, 2015, 2016c) had been applied extensively in PEC water splitting as for its low cost, non-toxic, and stable performance. Another effective way is selecting a suitable co-catalyst to improve the photo electrochemical performance and water oxidation activity in the process of assembling photo electrochemical device (Ran et al, 2014; Ding et al, 2017; Zhang Y. et al, 2018).
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