This first ever reference book that focuses on metalchalcogenide semiconductor nanostructures for renewable energyapplications encapsulates the state-of-the-art in multidisciplinaryresearch on the metal chalcogenide semiconductor nanostructures(nanocrystals, nanoparticles, nanorods, nanowires, nanobelts,nanoflowers, nanoribbons and more).
The properties and synthesis of a class of nanomaterials isessential to renewable energy manufacturing and this book focuseson the synthesis of metal chalcogendie nanostructures, their growthmechanism, optical, electrical, and other important properties andtheir applications in different diverging fields likephotovoltaics, hydrogen production, theromelectrics, lithiumbattery, energy storage, photocatalysis, sensors.
An important reference source for students, scientists,engineers, researchers and industrialists working onnanomaterials-based energy aspects associated with chemistry,physics, materials science, electrical engineering, energy scienceand technology, and environmental science.
Introduction: An Overview of Metal Chalcogenide Nanostructures for Renewable Energy Applications
Center of Research Excellence in Nanotechnology and Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia
*Corresponding author: email@example.com
In this chapter in the beginning global fossil fuel resources their current status and future anticipation and CO2 emissions its direct and indirect consequences are presented. Also significance of materials for renewable energy conversion systems as an alternative energy source is discussed. An overview of different metal chalcogenide semiconductors and their fascinating properties is reviewed. Various important (0-, 1-, 2-, and 3-dimensional) morphologies of chalcogenide nanostructures developed by different intriguing methods are illustrated followed by their important applications in renewable energy devices and their future outlook are discussed. The new class of metal chalcogenide nanostructures and their heterostructures offer outstanding prospect for the development of cost-effective, high-performance, smart, robust, and efficient energy conversion devices.
Keywords: Metal chalcogenide nanostructures, semiconductors, renewable enregy, metal sulphide, metal telluride, metal selenide nanostructures
Sustainable energy supply is essential for the profitable and societal structure of nations, and for the comfort of human lives. In the times when the demand of traditionally subjugated natural resources is surpassing supply, industrial growth has resulted in unwanted climatic changes and developing regions are contending for bigger share of restricted fuel stocks, the exploration for new methods to meet these supplies becomes more imperative. At present, more than 80% energy use is based on oil gas and coal. Figure 1.1 shows world energy usage from different sources including oil gas and coal . International energy agency (IEA) data from 1990 to 2008 reveal that the average energy use per person increased 10% whereas world population increased 27% [2, 3]. In the year 2008, total worldwide energy consumption was 474 exajoules (132,000 TWh) . This is equivalent to an average power use of 15 terawatts (TW) (2.0×1010 hp) .
Figure 1.1 Rates of energy usage (Ref. ).
Presently, the world uses energy at a rate of approximately 4.1 × 1020 joules/yr, which is equivalent to a continuous power consumption of 13 trillion watts, or 13 TW . With insistent conservation and advancement of energy efficiency measures, an increase in the Earth's population to 9 billion people escorted by fast technology expansion and economic growth worldwide, is anticipated to generate more than double the requirement for energy (to 30 TW) by 2050 . Sunlight is the largest source of all carbon-neutral energy. It is estimated that more energy from sunlight strikes the Earth in one hour (4.3 × 1020 J) than all the energy being consumed on the planet in a year (4.1 × 1020J) .
On the other hand, fossils fuel a major source of present energy will start depleting in coming decades. According to recent studies, anticipation of fossil fuel depletion by 2050 is shown in the figure (which is carried out by peak oil and gas 2007) . On the basis of these studies, it is important to understand that without viable options for supplying double or triple of today's energy use, the speedily developing world's economic, industrial, and technological prospects will be relentlessly restricted.
According to the recent report World Energy Outlook published by the IEA, world primary energy use will raise from 12 Gtoe (metric gigatons oil equivalent) in 2007 to 17 Gtoe in 2030, for typical yearly growth of 1.5% .
On the basis of IEA reports, which uses an energy production mix that comprises 80% fossil fuels, CO2 emissions will increase nearly 50% between 2007 and 2030 . The Intergovernmental Panel on Climate Change (IPCC) has shown that this increase could result in a 6°C elevation in temperature by the end of the century [6, 7]. Figure 1.3 shows photo-graphic image of a CO2 emission at site of an industrial plant .
Source: Association for the Study of Peak Oil and Gas, 2007 (Ref. ).
Figure 1.3 Photographic image for CO2 emission at an industrial plant (Ref. ).
Carbon dioxide emissions resulting from energy production are an environmental predicament. Recent efforts to resolve the CO2 emission include the famous summit (Kyoto Protocol) which is a UN agreement that intends to decrease harmful climate impacts signed by many countries . The main deliberation of this debate was to reduce green house gases (GHGs) emission in a time framework to be monitored by United Nations Framework Convention on Climate Change (UNFCCC) . Due to continuous unregulated industrial growth of developing and under-developed nations and struggle to attain technological progression by developed nations, air quality standards are decreasing tremendously. Figure 1.4 shows continuous CO2 production by 2050 and effect of alternative policy scenario (APS) if the IPCC policies are implemented apolitically and meritoriously [10, 11]. Very recent studies include dangerous effect of air pollution including size-dependent particulate matters (PMs) on lung cancer and cardiac diseases [12, 13]. There are apparent policies adopted by developed nations as a result of tight environmental regulations to transfer substantial production of their products to under-developed and developing nations due to low manufacturing cost and high-profit margin which also enormously contribute in CO2 emissions.
Figure 1.4 Global CO2 emissions based on IEA scenarios. Black line: the Reference Scenario (RS). Blue line: the APS from 2005 to 2030 and extrapolation to the ACT Map scenario in 2050. Red line: extrapolation from APS in 2030 to the TECH Plus scenario in 2050. Green line indicates CO2 emissions reduced by 2/3 in 2050 compared to emissions today. As such, the green line represents the IPCC target of 50-80% reduction in global CO2 emissions by 2050 (Ref. ).
Consequently, a paramount responsibility for IEA and other international institutions arises to sternly implement global standard with respect to increasing industrial growth and regulate physically the climate changes, which can minimize its harmful effects on humans in particular and living organism in general. Considering all these important prospective of fossil fuels' depletion, increasing pollution by the massive production of energy by various conventional sources, it is essential to explore the sources of renewable energy and more efficient strategies for energy storage and conversion into electrical or mechanical powers. The performance of conversion and storage devices strongly depends on the properties of their materials. Inventive materials chemistry predominantly new materials hold the key to indispensable advances in energy conversion and storage, both of which are essential in order to meet the challenge of global warming . The purpose of materials science is to endow with key solutions for the sustainable development of renewable energy. New and engineered materials science can meet the intimidating challenges, to harvest renewable energy from natural resources. It nevertheless has an essential part to play in attaining the ambitious target. In the past, material science has contributed drastically to progress in the safe, consistent and proficient use of energy and existing natural resources. The overall efficiency, effectiveness, and expediency of potential future energy sources or systems are directly related to many imperative materials factors. These important factors include nature of the materials, cost, availability and improvement in optical, chemical, mechanical, electrical, and thermal properties as well as capability to produce materials in different forms and shapes that work effectively in areas of energy generation storage and conversion. There is a significant relationship between energy efficiency, new avenues of energy, and materials science.
The worldwide market for advanced materials and devices used in renewable energy system was $18.2 billions in 2010; it is projected to approach 31.8 billion in 2016 increasing at compound annual growth rate (CAGR) of 7.4% which includes electromechanical and electronic devices, photovoltaic materials and devices, composite and reflective materials, and so on . Consequently, the need of materials study for energy conversion systems is a field of incredible opportunities for pragmatic and socially momentous applications.
1.2 Metal Chalcogenide Nanostructures
Systematic choice is a paramount for the material of a particular application which begins with desired properties and costs of candidate materials. Various organic and inorganic materials till now have been profoundly investigated for renewable energy conversion devices. Among them, semiconductor metal chalcogenides (sulfide, selenide, and telluride) received remarkable attention due to their intriguing chemical, optical, thermal, electrical, mechanical properties and optimal combination of decent conversion efficiency, ability to grow and deposit in ambient conditions, low band gap, band gap engineering, diverse crystal structures, nature to grow in layer forms, and so on . A chalcogenide is a chemical compound comprises of...