9:00 AM - EN07.06.02
Interfacial Engineered Colloidal “giant” Core/Shell Quantum Dots Sensitized Carbon Nanotubes-TiO2 Hybrid Photoanode for High-Efficiency Hydrogen Generation
Gurpreet Selopal1,2,Mahyar Mohammadnezhad2,Omar Abdelkarim2,Haiguang Zhao3,François Vidal2,Zhiming Wang1,Federico Rosei2,1
Solar-driven photoelectrochemical (PEC) hydrogen (H2) generation is an attractive approach for the sustainable production of clean and renewable fuels, to address future global energy demands [1-2]. However, the low photon-to-fuel conversion efficiency and long-term stability of PEC devices are major challenges to be addressed to enable large-scale commercialization. The sensitization of the wide band gap semiconductors with colloidal chalcogenide quantum dots (QDs) as light harvesters is an effective approach to extend the absorption spectrum toward the visible and near infrared region (NIR) region, leading to significant improvement of the PEC performance. A specially designed “giant” core/shell QDs exhibit superior optoelectronic properties such as better photophysical/chemical stability, suppressed non-radiative Auger recombination, improved quantum yield (QY), and improved exciton lifetime and the formation of quasi-type-II core/shell by tailoring the shell thickness/composition as well as the core size . Also, the carbon nanomaterials such as carbon nanotubes (CNTs), graphene, graphene nanoribbons and graphene oxide are widely used in various optoelectronic devices due to their unique structural and optoelectronic properties such as excellent conductivity, high mechanical strength and optical transparency . Herein, for the first time, we explore a simple, fast and cost-effective approach to fabricate high efficiency and stable PEC devices for H2 generation, by using a specially designed colloidal “giant” CdSe/(CdSexS1-x)5/(CdS)2 core/shell QDs as sensitizer and a hybrid photoanode with small amounts of CNTs into a TiO2 mesoporous film.
We will discuss the synergistic effect of promising optoelectronic properties of specially designed colloidal giant” CdSe/(CdSexS1-x)5/(CdS)2 core/shell QDs and improved electron transport (reduced charge transfer resistance) within the TiO2-CNTs hybrid anodes enabled by the directional path of CNTs to the photo-injected electrons towards FTO. Resulting, PEC devices based on TiO2/QDs-CNTs (T/Q-C) hybrid photoanode with optimized amount of CNTs (0.015 wt%), yield a saturated photocurrent density of 15.90 mA.cm-2 (at 1.0 VRHE) under one sun illumination (AM 1.5 G, 100 mW×cm-2), which is 40% higher than the reference device based on TiO2/QDs (T/Q) photoanodes. In addition, enhanced stability of the PEC device based on T/Q-C hybrid photoanodes (~19% loss of its initial photocurrent density) as compared with the T/Q photoanode (~35% loss) after two hours of continuous one sun illumination will be also presented and discussed in details. These results provide fundamental insights and a different approach to improve the efficiency and long-term stability of PEC devices and represent an essential step towards the commercialization of this emerging solar-to-fuel conversion technology.
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