Abstract
Highly ordered multi-leg TiO2 nanotubes (MLTNTs) functionalized with platinized cyanographene are proposed as a hybrid photoelectrode for enhanced photoelectrochemical water splitting. The platinized cyanographene and cyanographene/MLTNTs composite yielded photocurrent densities 1.66 and 1.25 times higher than those of the pristine MLTNTs nanotubes, respectively. Open circuit VOC decay (VOCD), electrochemical impedance spectroscopy (EIS), and intensity-modulated photocurrent spectroscopy (IMPS) analyses were performed to study the recombination rate, charge transfer characteristics, and transfer time of photogenerated electrons, respectively. According to the VOCD and IMPS results, the addition of (platinized) cynographene decreased the recombination rate and the transfer time of photogenerated electrons by one order of magnitude. Furthermore, EIS results showed that the (platinized) cyanographene MLTNTs composite has the lowest charge transfer resistance and therefore the highest photoelectrochemical performance.
Highlights
Photoelectrochemical (PEC) water splitting is a promising approach to the production of hydrogen, representing a clean, renewable, and sustainable technology for future energy systems
The results demonstrate that the surface functionalization of multi-leg TiO2 nanotubes (MLNTs) with G-CN and G-CN/Pt successfully decreased the overall charge carrier recombination rate and improved the charge transfer kinetics
The characteristic fingerprint of Pt was detected in the X-ray photoelectron spectroscopy (XPS) survey spectra, accompanied by the photoelectron peaks of G-CN
Summary
Photoelectrochemical (PEC) water splitting is a promising approach to the production of hydrogen, representing a clean, renewable, and sustainable technology for future energy systems. Hydrogen can yield more energy per unit mass than other fuels [1,2,3] and can be utilized in fuel cells producing only water as the reaction product. The core component of PEC cells is a semiconductor electrode, in which electron–hole pairs can be generated upon the light absorption [4,5], and can be further separated to provide corresponding redox half-reactions. TiO2 suffers from a few significant drawbacks that restrict its broader practical application. These are mainly the low solar light absorption due to its wide bandgap (~3.2 eV for anatase and 3.0 eV for rutile) and a relatively high recombination rate of photogenerated charge carriers [10,11,12]
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