Energy energy. SCI.: incredible! Cigarette butts are the best hydrogen storage materials

Hydrogen is a very attractive energy, especially for motor vehicles Because it has a high energy to weight ratio and does not produce carbon dioxide emissions Water is the main product of combustion, which is an excellent solution to the greenhouse gas problem caused by carbon dioxide emission from fossil fuel combustion Compared with the huge risk of nuclear energy, hydrogen is extremely rich, and the risk is similar to that of natural gas when it is used Moreover, there is no problem of carbon monoxide generated due to insufficient combustion, and the emission is non toxic water, which can be said to be the perfect zero emission green energy Hydrogen can be used to make fuel cells Hydrogen fuel cell is a kind of redox cell, in which the chemical energy of hydrogen is converted into electric energy by using oxidant (usually oxygen) Cars that use hydrogen fuel cells will burn hydrogen in a similar way to internal combustion engines The 2020 target set by the United States Department of energy (DOE) for hydrogen powered vehicles includes an energy to weight ratio of 1.8kwh kg-1 (5.5wt% H2) and an energy density of 1.3kwh L-1 (0.040 kgl-1) The use of solid materials is considered to be a feasible way to achieve the desired goal of hydrogen storage At present, the hydrogen storage materials under study can be roughly divided into two categories, one is to store hydrogen through chemical adsorption, including various metal hydrides The other kind of hydrogen storage materials use physical adsorption, usually using highly porous materials with high surface area, such as metal organic frameworks (MOFs) and covalent organic frameworks (COFS) Now it is clear that the hydrogen storage capacity of porous solid materials depends on the surface area and the existence of micropores High surface area is favorable for good absorption, while the existence of micropores improves porosity, and then improves surface area Element analysis of Hydrochar (source: Energy Environ.Sci The goal of looking for new hydrogen storage materials is to have new or improved performance materials, to be easier and cheaper to prepare, and to be sustainable The improved performance can be generated by customized design based on the knowledge needed for hydrogen storage, and sustainability can be achieved by increasing production routes relative to starting materials As a part of carbon materials with optimized hydrogen storage, cellulose based precursors have recently been found to be good starting materials for porous carbon materials This is particularly beneficial in terms of waste recycling, as cellulose derivatives (i.e cellulose acetate) are the main components of cigarette filter tips The waste cigarette filter tip in the form of cigarette butts is a kind of common waste and harmful to the environment Because cellulose acetate is not biodegradable Every year, the number of cigarettes smoked in the world is up to 5.8 trillion, generating 800000 tons of cigarette butts Pollutants in cigarette filter, especially toxic heavy metals, will be further harmed These pollutants will penetrate into the water and may cause harm to human beings and wildlife Therefore, it is obvious that cigarette butts are environmental problems that need to be solved If cigarette butts are not discarded, but can make high-value products and gain value-added, it will be a very ideal situation Since they are mainly composed of cellulose acetate, it is a potential idea to make cigarette butts into porous materials Hydrochar's thermogravimetric analysis (source: energy energy SCI.) Robert mokaya and Troy Blankenship of the University of Nottingham are exploring how to convert this hazardous waste into hydrogen storage materials It has been used to filter cigarettes into porous carbon However, so far, there is no precedent for the preparation of activated carbon from cigarette filter tip and waste cigarette butts In this study, they explored the preparation of activated carbon from cigarette filters and discarded cigarette butts, and evaluated the hydrogen absorption capacity of the carbon produced This study revealed the activation conditions and the properties of the activated carbon In particular, some unexpected cases of porosity, and how to affect hydrogen absorption capacity The research team first collected cigarette butts and heated them to 250 ℃ with water Under high pressure, a kind of material called hydrochar, which contains carbon and oxygen spheres at nanometer level, will be produced Next, they activated the material with potassium hydroxide at 800 ℃ to produce carbonates that can be broken down into carbon dioxide, leaving behind highly porous materials The hydrogen absorption data of hydrochar (source: energy energy SCI.) the hydrothermal carbonization of cigarette filter tip and waste cigarette end produces hydrochar When it is activated, it produces porous carbon (up to 4300m2g-1) with extremely high apparent surface area (with oxygen functional groups such as COOH, c-oh and C = O) and large surface area (up to 3867m2g-1), which are produced by micropores The effect of temperature on the porosity of activated cigarette butts shows abnormal behavior, that is, the highest surface area and pore volume are achieved at 600 ℃, and then the activation is reduced at higher temperature This abnormal trend is due to the presence of a large number of divalent metals in hydroquinone derivatives used as starting materials in cigarettes In addition to Koh, metal additives (k, CA, Na, Mg, etc.) also act as activators Due to the combined effect of high surface area, high porosity and oxygen rich properties, the hydrochar shows an unprecedented hydrogen storage capacity of 8.1wt% The total absorption of 9.4wt% at - 196 ℃ and 20bar was 10.4wt% and 11.2wt% at 30 and 40 bar, respectively The hydrogen content of most activated carbon is between 4% and 6wt% Hydrochar, a new material from cigarette butts, has a high application value Their results provide new insights into the value of major waste treatment as attractive energy materials and the highest hydrogen absorbing material reported to date for any carbon or porous material The research results are directly related to the environmental pollution, which provides a new research direction for the research of carbon based sustainable energy storage materials At the same time, it also puts forward a problem worthy of attention, that is, whether raising the price can solve the thorny problem of cigarette butts Brief introduction of corresponding author: http:// paper link: http://pubs.rsc.org/en/content/articlelanding/2017/ee/c7ee02616a ා! 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