Renewable Energy Global Innovations features: Graphene oxide/WS2/Mg-doped ZnO nanocomposites for solar-light catalytic and anti-bacterial applications

Significance Statement

Semiconductor oxides find an array of applications in water purification for photocatalytic degradation of organic dyes. Zinc oxide is perhaps the most popular component for photocatalytic applications owing to its wide band gap, low cost, environmental friendliness, and large exciton binding energy leading to superior optical activity. This makes zinc oxide an important ingredient for photo catalyst for organic pollutants treatments.

However, high recombination rate of electron-hole pairs in semiconductors as well as insufficient solar spectrum absorption limit its photocatalytic reaction efficiency. Doping, constructing heterojunctions and catalyzer carrier are viewed as solutions to these problems, and are used mainly to enhance the photocatalytic activity of zinc oxide nanostructure. Doping the zinc oxide with a suitable element is an important approach for improving its sunlight absorption.

Catalyzer carrier is viewed as an effective approach for decreasing recombination rate of photo generated electron-hole pairs. Graphene is an important catalyst support, which has been deemed as the most promising building block to trap and transfer the photo-induced electrons because of its large surface area, high carrier capacity, and large electronic storage ability. Graphene can fix zinc oxide nanoparticles defects for conducting electron and function as a conducting network. It can as well prevent zinc oxide from aggregation and result in the improvement of the photocatalytic performance.

A group of researchers led by Professor Yuenhong Tsang at The Hong Kong Polytechnic University Shenzhen Research Institute demonstrated the scalable approach to fabricate large amount of tungsten disulfide Nano plates through the mechanical shear exfoliation approach. They adopted a versatile method to produce 3D reduced graphene oxide-tungsten disulfide nanosheet magnesium doped zinc oxide hybrid implementing a layer-by-layer assembly method. They achieved photocatalytic attributes enhancement adopting the 3D graphene tungsten disulfide hybrid. Their work is published in Solar Energy Materials & Solar Cells.

The authors used Rhodamine as a model dye in a bid to evaluate the photocatalytic activity of the specimens. The research team computed the degradation ratio as the quotient between original concentration and the residual concentration at varying time. After a complete degradation of the Rhodamine, the authors isolated the graphene nanocomposites and added them to a different solution with the same Rhodamine concentration. This was in a bid to analyze the photocatalytic stability of the resulting composites.

The authors observed the adsorption ability of the specimen before opening light in order to differentiate adsorption effect and photocatalytic ability of the samples for Rhodamine. They realized that the adsorption ratio of all samples for Rhodamine was less than 10% in the dark. When exposed to about 100W UV light irradiation, the group without a photo catalyst indicated about 20% photo degradation. However, a 60% photo degradation was recorded when reduced graphene oxide/magnesium doped zinc oxide composites samples were imported.

However, a 90% removed rate of reduced graphene oxide-tungsten disulfide nanosheet magnesium doped zinc oxide hybrid for Rhodamine was recorded after 5 min, and the Rhodeamine was completely removed after 10min.

Inhibition rings sizes against E, coli as well as S. aureus were 8.64mm and 6.07mm respectively for magnesium doped zinc oxide specimen.  However, when graphene was introduced, the rings sizes increased to 9.23mm and 10.21mm.

Tungsten disulfide nanosheet played a critical role in improving photocatalytic and antibacterial activity of the magnesium-doped zinc oxide composite. The outcomes of the study prove that the resulting 3-D tungsten doped zinc oxide composites could be good candidates for sunlight-driven photocatalytic, self-cleaning, environmental protecting, and photovoltaic applications.

About The Author

Dr. Yuen Hong Tsang has completed his undergraduate and PhD study in the School of Physics and Astronomy, The University of Manchester, UK in 2004. He came back to Hong Kong in 2009 and he is now Assistant Professor in Applied Physics Department, The Hong Kong Polytechnic University. He has published >100 SCI international peer reviewed journals with H-index >20 and total citation >1400.

His current research interests include development of novel materials, e.g. graphene, MoS₂, WS₂ etc. for laser photonics, photo-catalysis, solar energy conversion applications, e.g. photo-catalyst, solar heat absorber, saturable absorber, optical limiter, photo detection, fiber laser, Q-switched and mode locked lasers, etc. He has involved and successfully completed several research projects funded by some well-known international companies.

These projects include 1.  Laser range funder for military applications (funded by Thales.) 2. Imaging system for dental applications (funded by Colgate Palmolive) 3. Narrow linewidth tunable lasers (funded by Huawei) 4. Carbon based mode locking laser system (funded by Fianium Asian Ltd.)

Reference

Chuansheng Chen, Weiwei Yu, Tiangui Liu, Shiyi Cao, Yuenhong Tsang. Graphene oxide/WS2/Mg-doped ZnO nanocomposites for solar-light catalytic and anti-bacterial applications. Solar Energy Materials & Solar Cells, volume 160 (2017), pages 43–53.

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Renewable Energy Global Innovations features: Assessment on the Research Trend of Low-Carbon Energy Technology Investment: A Bibliometric Analysis

Significance Statement

As a result of high carbon emission which leads to global warming, there exists a persistent desire to create an alternative route for energy supply from renewable sources. The fusion of low-carbon energy technologies, which is a form of renewable energy to the developing world would not only reduce emission of carbon particles but also satisfy energy demand.

Despite the use of bibliometric analytical method of study and evaluation of previous research with focus on low-carbon technology investment, there exists a need for more detailed bibliometric strategy to provide an encompassing knowledge in this field.

Dr. Zhifu Mi and colleagues conducted a comprehensive bibliometric analysis from obtainable literatures in order to find the research status and trend in line with that of the low-carbon energy technology investment, coupled with measurements of comprehension strength between countries, followed by a frequency analysis of keywords to discover research hot topics as a base for future assessment and lastly, provision of relevant ideas needed for the future development and investment of low-carbon energy technology. The paper is now published in the journal, Applied Energy.

The authors made use of databases of Science Citation Index Expanded from 1981 to date and that of Social Sciences Citation Index dating back to 2002. They also considered some characteristic terms such as general statistics, number of countries’ publications, journal and subject distributions, authors and institution statistics, academic collaboration, article citation and comprehensive strength in the field of low-carbon energy technology investment among countries from 2121 publications.

Following the trends of top 10 productive countries, two stages were observed from the year 1985 to 2013; the first stage with stable development from 1985 to 2014 with research growth rate of 13.15%, and the second, with rapid development from 2005 to 2013 with research growth rate of 29.06%. This shows that the low-carbon energy technology investment has reached the rapid development stage.

The USA had the highest number of publications, followed by European countries of Germany and UK, and the fourth was China. Highest number of publications was observed in developed countries compared to the developing ones, but a decrease in disparity as years go by was also envisaged.

Energy Policy had the highest number of total publications, followed by Renewable Energy and Energy. However, the highest citations per publications were found in the journals of Biomass Bioenergy followed by International Journal of Hydrogen Energy and Solar Energy. They also found Energy Fuel journal followed by the journals of Environmental Sciences Ecology and Engineering to have the highest number of subjects related to the low-carbon energy technology investment.

The national comprehensive strength of the USA, in the field of the low-carbon technology was the highest followed by the UK. European countries dominated the top 15 productive countries with inclusion of developing countries of China and Turkey.

When the authors analysed the frequency of keywords, “renewable energy” was discovered to be the mostly used. “Carbon capture and storage” was observed to be an emerging keyword with an upward trend, followed by the frequently used “electricity”. Research hotspots with keywords such as “policy”, “real option theory” and “uncertainty” are also developing rapidly.

This study was able to provide a broad bibliometric method which analyzed the investment in low-carbon energy technology for future assessments.

About The Author

Dr. Zhifu Mi is a Senior Research Associate in the School of International Development, University of East Anglia (UEA) and Senior Research Fellow in the Tyndall Centre for Climate Change Research. He is a Managing Guest Editor of Journal of Cleaner Production (IF=4.959). His research is focused on climate change mitigation, energy policy, and climate change economic theories and modelling. He has authored over 20 articles in peer-reviewed journals.

He was invited to write a review article entitled Integrated Assessment Models (IAMs) for Climate Change in Oxford Bibliographies which invites top scholars and researchers in the field to contribute. He has served as an Author for Chapter 37 on International Policies and Actions to Tackle Climate Change in the Third National Assessment Report on Climate Change which is known as Chinese “IPCC Assessment Report”.

Journal Reference

H. Yu^1,2,3,4, Y.M. Wei^1,2,3, B.J. Tang^1,2,3, Z. Mi^1,5, S.Y. Pan^1,2,3, Assessment on the Research Trend of Low-Carbon Energy Technology Investment: A Bibliometric Analysis, Applied Energy 184 (2016) 960–970.

Show Affiliations

1. Center for Energy and Environmental Policy Research, Beijing Institute of Technology, Beijing 100081, China
2. School of Management and Economics, Beijing Institute of Technology, Beijing 100081, China
3. Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing 100081, China
4. Visitor of Energy Policy Research Group, University of Cambridge, Cambridge CB2 1AG, UK
5. School of International Development, University of East Anglia, Norwich NR4 7TJ, UK

 

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