1:30pm - 2:00pmInvited
Solar Steam Generation for Water Treatment
Nanjing University, China
Water scarcity is one of the most pressing global challenges. Nanomaterials with carefully tailored properties can be used to manipulate the flow of phonons, electrons and photons, to enable unconventional solution to addressing this issue. In this talk, I will present our recent progress in solar steam generation for water treatment. We report a plasmon-enhanced solar desalination device. This most efficient and broad-band plasmonic absorber is fabricated through self-assembly of metallic nanoparticles onto a nanoporous template by one step deposition process. Because of its efficient light absorption and strong field enhancement, it can enable very efficient and effective solar desalination by using low cost aluminum nanoparticles. Inspired by the transpiration process in plants, we report an artificial transpiration device with a unique design of two dimensional water path. With efficient two dimensional water supply and suppressed heat loss, it can enables an efficient (80% under one-sun illumination) and effective (four orders salinity decrement) solar desalination device. More strikingly, the energy transfer efficiency of this artificial transpiration device is independent of water quantity and can be achieved without extra optical or thermal supporting systems, therefore significantly improve the scalability and feasibility of this technology.
2:00pm - 2:15pmOral
Plasmonic Photothermic Directed Broadband Sunlight Harnessing for Seawater Catalysis and Desalination
1Department of Electrical and Computer Engineering, National University of Singapore, Singapore; 2Engineering Science Programme, National University of Singapore, Singapore; 3Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), Singapore
Using readily available renewable resources i.e. solar energy and seawater to secure sustainable fuel and freshwater for humanity is an impactful quest. Here, we have designed solar thermal collector nanocomposites (SiO2/Ag@TiO2 core-shell) that possess efficient photothermic properties for highly targeted interfacial phase transition reactions that are synergistically favorable for both seawater catalysis and desalination reactions. The photothermic effect arises from plasmonic metal nanoparticles exhibits localized interfacial heating which directly triggers surface-dominated catalysis and steam generation processes, with minimal heat losses, reduce thermal masses and optics implementation. The solar thermal collector nanocomposites are seawater and photo stable for practical solar conversion of seawater to simultaneously produce clean energy and water. Finally, a proof-of-concept all-in-one compact solar hydrogen and distillate production prototype demonstrates the viability of sustainable photothermic driven catalysis and desalination of seawater under natural sunlight. Importantly, this approach holds a great promise for enhancing energy and water productivity without considerable capital, infrastructure and environment ramifications.
2:15pm - 2:30pmOral
Core-Shell Based Composite SnO2NPs@ZIF-8 as an Effective Photo-catalyst for Degradation of Methylene Blue in Wastewater Treatment
Indian Institute of Technology Roorkee, India
The development of an easily executable heterogeneous photocatalytic method/material used for wastewater treatment to degrade organic pollutants (dyes) is the most challenging industrial problem from the environmental pollution point of view. Organic dyes are usually toxic, carcinogenic and mutagenic with low biodegradability and their discharge into the water bodies misbalances the aquatic ecosystem. Several semiconducting metal oxides nanoparticles (e.g., ZnO, Fe2O3, TiO2, SnO2 etc.) were extensively used for their removal prior to the discharge of wastewater effluents, but the problem of agglomeration of NPs reduces their efficiency which can be partially solved by their immobilization/encapsulation. An easily executable method to synthesize core-shell based composite, SnO2NPs@ZIF-8 by in situ encapsulation of SnO2NPs within ZIF-8 (zeolitic-imidazolate frameworks) in methanol at room temperature was developed. Encapsulation of SnO2NPs within ZIF-8 cavity was confirmed by powder X-ray diffraction, transmission electron microscopic and evidenced by lowering of the surface area determined by Brunauer‒Emmet‒Teller adsorption studies. ZIF-8 and SnO2NPs@ZIF-8 have similar morphology as evidenced by scanning electron microscopic images and have high thermal stability in air and N2 atmosphere. A slight lowering of band gap (determined by UV-DRS spectra) of SnO2NPs from 3.54 to 3.18 eV and that of ZIF-8 from 5.26 to 4.93 eV indicates the definite shift of micro-environment of SnO2NPs within the ZIF-8 cavity. SnO2NPs@ZIF-8 composite was used as a photo-catalyst for degradation of methylene blue under UV-Visible irradiation and we studied the effects of various factors such as loading amount of SnO2NPs (150, 300 and 500 µL suspension of SnO2NPs), catalyst’s amount, pH and initial dye concentration. The composite (10 mg; prepared by encapsulation of 150 µL suspension of SnO2NPs) photo-degraded 95% of methylene blue (5×10-5M) solution at pH 11.5. The experiments on the electrochemical performance of SnO2NPs@ZIF-8 composite are under progress.
2:30pm - 2:45pmOral
Nanostructured Carbon film for Electricity Generation from Evaporation Driven Water Flow
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, China
Evaporation of water is a ubiquitous process in natural environmental, which is also a dominant form of energy transfer in the earth’s climate. Due to the large latent heat of vaporization, water evaporation process involves with large amount of energy exchange, thus has been utilized as an efficient way to enhance thermal energy transfer in many important daily and industrial applications, such as transpiration cooling and heat pipe. Here we present that water evaporation from the porous carbon film, the lowest-cost nanostructured carbon material, can reliably generate voltage up to 1 V under ambient conditions, which are orders of magnitude higher than recent reports of electrical potential from carbon materials (e.g. CNT, graphene) and large enough for powering existing electronic devices directly. Intensive investigations revealed that the evaporation-induced water flow within the porous carbon generates the electricity. The output performance of the device can be easily scaled up and used to power low-power consumption electronic devices or for energy storage. Furthermore, the device was successfully used without electric storage as a direct power source for electrodeposition and organic dye degradation. Due to the ubiquity of evaporation in nature and the low cost of materials involved, our study presents here shows a novel avenue to harvest ambient energy and has great potential in the low cost, green self-powered devices and systems.
 Jun Zhou, Wanlin Guo et al., Water-evaporation-induced electricity with nanostructured carbon materials, Nat. Nanotechnol. 2017, DOI: 10.1038/nnano.2016.300
 J. Zhou et al., Induced Potential in Porous Carbon Films through Water Vapor Absorption, Angew. Chem. Inter. Edit. 2016, 55, 8003-8007.
 J. Zhou et al., Flexible microfluidics nanogenerator based on the electrokinetic conversion, Nano Energy 2016, 30, 684-690.
2:45pm - 3:00pmOral
Electrospun TiO2 Mesostructures Sensitized by Quantum Dots for Photovoltaic Application
1State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, China; 2Centre for Nanofibers and Nanotechnology, National University of Singapore, Singapore
Development of low-cost quantum dot-sensitized solar cells (QDSCs) with intermediate efficiency is of great interests among global researchers. Here a rice grain-shaped TiO2 mesostructure was produced by electrospinning a polymeric solution containing titanium isopropoxide, polyvinyl acetate and acetic acid in N,N-dimethyl acetamide followed by calcination at 500 oC. CdS quantum dots were then deposited on the mesoporous ‘rice grains’ by successive ionic layer adsorption and reaction (SILAR) method. Promising photovoltaic performance of an overall power conversion efficiency was obtained in the presence of a methanol-free polysulfide electrolyte under standard 1-sun illumination of 100 mW/cm2. We attribute the superior performance to the compromise of the high surface area of spherical nanoparticles and the directed electron transport capability of continuous nanofibers due to the unique inter-connected rice grain-like structure. Without any elaborate and complicated fabrication procedures typically involved in dye-sensitized solar cells (DSCs), the present methodology is also believed to provide a promising mass production way for alternative low-cost solar cells in view of the fact that both electrospinning and SILAR are generally considered as simple and scalable techniques.
3:00pm - 3:30pmKeynote
Solar Energy to Chemical Energy: From Photocatalysis to Photothermal Catalysis
Peking University, China
Converting solar energy to chemical energy is one of the efficient way to overcome its intermittency. In this talk, I will introduce the recent progress in our group on this research topic, which include: 1) A hybrid system consist of CdS nanocrystals, CoCl2•6H2O and 2,2’-bipyridine was studied for photocatalytic reduction of CO2. The results showed the hybrid system could reduce CO2 into CO coupling in acetonitrile under visible light irradiation. The measured photonic efficiency of CO formation was 1.0% under monochromatic irradiation at λ = 470 nm. 2) Splitting of alcohols into hydrogen and corresponding carbonyl compounds has potential applications in hydrogen production and chemical industry. We have developed a heterogeneous photocatalyst (Ni-modified CdS nanoparticles) which could efficiently split alcohols into hydrogen and corresponding aldehydes or ketones under visible light irradiation. 3) Photothermal-enhanced catalysis was achieved in the core-shell Cu7S4 hollow microsphere@ZIF-8 heterostructures via the near-infrared localized surface plasmon resonance. Under the laser irradiation (1450 nm, 500 mW), the cyclocondensation reaction rate increased 4.5-5.4 fold compared to that of the process at room temperature. More generally, this approach provides a platform to improve the reaction activity with efficient utilization of solar energy.