Other Applications
Besides their applications in energy storage and conversion, MXenes and MXene-based hybrids and composites have also found a wide range of applications in other fields, such as environmental protection, chemical sensors, biosensors, microwave absorbers, E
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Other Applications
5.1 Introduction Besides their applications in energy storage and conversion, MXenes and MXenebased hybrids and composites have also found a wide range of applications in other fields, such as environmental protection, chemical sensors, biosensors, microwave absorbers, EMI shielding and transparent thin films (electrodes or conductors), as well as other applications that are not covered in this book [1–9]. The applications of MXenes and their hybrids/composites in environmental protection will be first introduced, which include the removal of heavy metallic polluting ions (e.g., Hg2+ , Cd2+ , Cr3+ etc.), organic molecules (e.g., Rhodamine B and methyl orange) and radionuclide pollutants. For sensing applications, there will be chemical sensors, biochemical sensors, electrochemical sensors, piezoelectric sensors, gas sensors and so on. Electromagnetic inference (EMI) shielding and microwave absorption are the utilization of the MXene-based materials with different functionalities, where EMI is to use their high electrical conductivity and microwave absorbing is mainly achieved by combining with other components. Finally, MXene-based thin films have been employed as electrodes in flexible electronic devices.
5.2 Environmental Remediating Agents Pollution has been a worldwide issue, which draws attentions from researchers of various fields. Heavy metallic ions, toxic organic compounds, bio-toxins and toxic gases are among the most serious pollutants. To address this problem, various physical, chemical and biological methods have been proposed and implemented, such as membrane filtrations, precipitations, adsorptions, solvent extractions, ion exchanges and so on [10–12]. Comparatively, adsorption is among the most cost-effective and simplest ones [13]. Also, adsorption has no problem of secondary pollution, because
© Springer Nature Switzerland AG 2021 Z. Xiao et al., MXenes and MXenes-based Composites, Engineering Materials, https://doi.org/10.1007/978-3-030-59373-5_5
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5 Other Applications
no harmful substances are produced in the process. To ensure the adsorption to effective and efficient, the adsorbents should have a sufficiently large specific surface area and appropriate functionalities, depending on characteristics of the adsorbates. In this regard, porous materials, such as activated carbons, kaolinites, zeolites, chitosans, metal–organic frameworks and so on, are promising adsorbents to remove the environmental pollutants [14–17]. It is well known that materials with low dimensions usually have large specific surface area and thus can be used as adsorbents for removal of pollutants, such as ordered mesoporous silica, carbon nanotubes, graphenes and phosphorenes [18–21]. Therefore, it is reasonable to expect that 2D MXenes could be promising candidates as adsorbents for the applications in environmental pollutant purification [22].
5.2.1 Adsorption of Heavy Metallic Ions Heavy metal ions, such as Pb(II), Cr(IV), Hg(II), Cd(II) and Cu(II), are highly toxic, so that they are ver
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