Enhanced catalytic properties from platinum nanodots covered carbon nanotubes for proton-exchange membrane fuel cells

An efficient fabrication method for carbon nanotube (CNT)-based electrode with a nanosized Pt catalyst is developed for high efficiency proton-exchange membrane fuel cells (PEMFC). The integrated Pt/CNT layer is prepared by in situ growth of a CNT layer on carbon paper and subsequent direct sputter-deposition of the Pt catalyst. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrate that this Pt/CNT layer consists of a highly porous CNT layer covered by well-dispersed Pt nanodots with a narrow size distribution. Compared with conventional gas-diffusion layer assisted electrodes, the CNT-based electrode with a Pt/CNT layer acting as a combined gas-diffusion layer and catalyst layer shows pronounced improvement in polarization tests. A high maximum power density of 595 mW cm⁻² is observed for a low Pt loading of 0.04 mg cm⁻² at the cathode.     

Effective design of barrier enclosure to contain aerosol emissions from COVID-19 patients

Facing shortages of personal protective equipment, some clinicians have advocated the use of barrier enclosures (typically mounted over the head, with and without suction) to contain aerosol emissions from coronavirus disease 2019 (COVID-19) patients. There is, however, little evidence for its usefulness. To test the effectiveness of such a device, we built a manikin that can expire micron-sized aerosols at flow rates close to physiological conditions. We then placed the manikin inside the enclosure and used a laser sheet to visualize the aerosol leaking out. We show that with sufficient suction, it is possible to effectively contain aerosol from the manikin, reducing aerosol exposure outside the enclosure by 99%. In contrast, a passive barrier without suction only reduces aerosol exposure by 60%.     

Synthesis of PANI‐CaO composite nanofibers with controllable diameter and electrical conductivity

We report the direct evidence of the control of diameter, surface morphology, and conductivity of polyaniline (PANI) nanofibers by systematically varying the addition of CaO in the range from 0.005 to 1.00 g. The possible incorporation of CaO in PANI was revealed by Fourier transform infrared spectroscopy and ultraviolet–visible spectroscopy. The diameter of PANI nanofibers was varied with the variation of CaO loadings. The low diameter, 30 nm was obtained for the highest loading of CaO (1.00 g). Field emission scanning electron microscopy analysis showed that the addition of CaO between the range of 0.005 and 1.00 g, always produces nanofibers with regular and uniform surface morphology and without secondary growth and agglomeration of primary nanoparticles. Conductivity measurements showed that the highest conductivity value of 6.329 S cm⁻¹ could be obtained by the addition of the lowest amount of CaO (0.005 g). Furthermore, we observed the decreasing trend of conductivity with the increasing of CaO loadings. POLYM. COMPOS., 36:359–366, 2015. © 2014 Society of Plastics Engineers     

Hydrothermal Growth of TiO2 Nanorod Arrays and In Situ Conversion to Nanotube Arrays for Highly Efficient Quantum Dot‐Sensitized Solar Cells

TiO₂ nanorod (NR) and nanotube (NT) arrays grown on transparent conductive substrates are attractive electrode for solar cells. In this paper, TiO₂ NR arrays are hydrothermally grown on FTO substrate, and are in situ converted into NT arrays by hydrothermally etching. The TiO₂ NR arrays are reported as single crystalline, but the TiO₂ NR arrays are demonstrated to be polycrystalline with a bundle of 2–5 nm single crystalline nanocolumns grown along [001] throughout the whole NR from bottom to top. TiO₂ NRs can be converted to NTs by hydrothermal selective etching of the (001) core and remaining the inert sidewall of (110) face. A growth mechanism of the NR and NT arrays is proposed. Quantum dot‐sensitized solar cells (QDSCs) are fabricated by coating CdSe QDs on to the TiO₂ arrays. After conversion from NRs to NTs, more QDs can be filled in the NTs and the energy conversion efficiency of the QDSCs almost double.     

A wireless, passive carbon nanotube-based gas sensor

A gas sensor, comprised of a gas-responsive multiwall carbon nanotube (MWNT)-silicon dioxide (SiO₂) composite layer deposited on a planar inductor-capacitor resonant circuit is presented here for the monitoring of carbon dioxide (CO₂), oxygen (O ₂), and ammonia (NH₃). The absorption of different gases in the MWNT-SiO₂ layer changes the permittivity and conductivity of the material and consequently alters the resonant frequency of the sensor. By tracking the frequency spectrum of the sensor with a loop antenna, humidity, temperature, as well as CO₂ , O₂ and NH₃ concentrations can be determined, enabling applications such as remotely monitoring conditions inside opaque, sealed containers. Experimental results show the sensor response to CO₂ and O₂ is both linear and reversible. Both irreversible and reversible responses are observed in response to NH₃, indicating both physisorption and chemisorption of NH₃ by the carbon nanotubes. A sensor array, comprised of an uncoated, SiO₂ coated, and MWNT-SiO₂ coated sensor, enables CO₂ measurement to be automatically calibrated for operation in a variable humidity and temperature environment     

Conventional and holistic urban stormwater management in coastal cities: a case study of the practice in Hong Kong and Singapore

This study compares stormwater management in two coastal cities: Hong Kong and Singapore. Hong Kong adopted conventional urban stormwater management for flood control and embraced hard-engineering infrastructure in the scheme. In contrast, Singapore has put in place a series of holistic management practices to manage urban runoff. By comparing the stormwater management practices in these two cities, the differences in approaches to non-structural and structural practices were elucidated. Life cycle costing and environmental benefit analysis indicate that holistic urban stormwater management can lead to higher economic efficiency, sustainability and environmental friendliness, compared to conventional urban stormwater management.     

Post-combustion carbon dioxide capture: Evolution towards utilization of nanomaterials

Carbon dioxide (CO₂) is not the gas that gives the most severe global warming impact among the greenhouse gases (GHGs). However, its highest annual emission into the atmosphere makes it the most imperative anthropogenic GHG. This elevated emission is primarily coming from fossil fuel power plants. Hence, post-combustion CO₂ removal from power plants becomes crucial in global warming mitigation as it can be retrofitted directly into an existing plant. CO₂ removal technology nowadays is utilizing solvent-based sorbents, such as amine solutions and ionic liquids. Many extensive research works have been carrying out to improve the constraints of existing technology. In this paper, a general review on existing CO₂ removal technologies, existing research works on CO₂ removal sorbents was done. In conjunction with that, we will look into the potential and development of nanomaterials as CO₂ removal sorbents in the future. Nanomaterials have shown their potentials in CO₂ capture with its high surface area and adjustable properties and characteristics. Many limitations in existing technology were found improvable by nanomaterials.     

Global warming mitigation and renewable energy policy development from the Kyoto Protocol to the Copenhagen Accord—A comment

Global warming is a grave environmental issue that has caught the attention of the globe. Due to the consequences of global warming, UNFCCC has established the Kyoto Protocol and the Copenhagen Accord as measures of combating climate change due to the emission of greenhouse gases. It has been three years since the first commitment period of the Kyoto Protocol and the Copenhagen Accord was just newly established. Therefore, there is a necessity to evaluate the performance of the Kyoto Protocol and to comment upon the Copenhagen Accord in its contributions toward climate change mitigation. Major greenhouse gas (GHG) emitters who are among the Kyoto Protocol ratifying developed nations exhibit the potential to achieve the desired Kyoto pledges through the aid of Clean Development Mechanisms (mainly from using renewable energy), as proposed in the Kyoto Protocol. However, the nullifying effects from non-ratified major emitters like the US and ratified but still developing countries have difficulties in adhering to the Kyoto Protocol. The Copenhagen Accord, on the other hand, is considered to be less ambitious and provides limited financial aid through the Copenhagen Green Climate Fund. The formulation of such a document indicates that modern societies continues to waste time in negotiations that emphasize on individual economic and political advantages, rather than taking into account true global considerations. It raises questions regarding how much time is needed before we decide to fully commit to the effective and collective efforts of climate change mitigation.     

Online Ensemble Modeling for Real Time Water Level Forecasts

Accurate and reliable flood forecasting is essential to mitigate the threats brought by floods. Ensemble approaches have been used in limited studies to improve the forecasts of component models. In this paper an ensemble model based on neural-fuzzy inference system (NFIS) and three real time updating approaches were used to synthesize the water level forecasts from a Adaptive-Network-based Fuzzy Inference System (ANFIS) model and the Unified River Basin Simulator (URBS) model for three stations in Lower Mekong. The NFIS ensemble model results are compared with the simple average model (SAM) which is adopted as a benchmark ensemble model. The ensemble model of offline learning without real time updating (EN-OFF), ensemble model with real time updating using offline learning (EN-RTOFF), ensemble model with real time updating using online learning (EN-RTON1) and ensemble model with real time updating using online learning and sub-models (EN-RTON2) were studied in this paper. Statistical analysis of the models for all the three stations indicated the superiority of the EN-RTON2 model over EN-RTOFF, EN-RTON1 models, SAM and the EN-OFF model. Not only the spikes in the URBS model were eliminated, but also the time shift problems in the ANFIS model results were decreased.     

Laser Imagery Technique for Measuring Dispersed Droplets in Water

A nonintrusive method, based on the planar laser imagery technique, was developed to capture images of droplets dispersed in turbulent flow without disturbing the flow field. The methodology and technique of capturing the images, processing, recognition, and measurement were presented. Experimental findings show that this is a workable method in laboratory investigations of droplet dispersion. Results of droplet size distribution obtained and their comparison with those in the literature indicated that the proposed nonintrusive method was successful at capturing fast-moving droplets in turbulent flow without disturbing the flow field. The image processing methodology adopted to recognize and measure the droplets was found to be efficient and effective. The results of the normalized droplet size distribution (number frequency) depicts clearly discernible self-similarity characteristics.