Mercury pollution threatens the environment and human health across the globe. This neurotoxic substance is encountered in artisanal gold mining, coal combustion, oil and gas refining, waste incineration, chloralkali plant operation, metallurgy, and areas of agriculture in which mercury‐rich fungicides are used. Thousands of tonnes of mercury are emitted annually through these activities. With the Minamata Convention on Mercury entering force this year, increasing regulation of mercury pollution is imminent. It is therefore critical to provide inexpensive and scalable mercury sorbents. The research herein addresses this need by introducing low‐cost mercury sorbents made solely from sulfur and unsaturated cooking oils. A porous version of the polymer was prepared by simply synthesising the polymer in the presence of a sodium chloride porogen. The resulting material is a rubber that captures liquid mercury metal, mercury vapour, inorganic mercury bound to organic matter, and highly toxic alkylmercury compounds. Mercury removal from air, water and soil was demonstrated. Because sulfur is a by‐product of petroleum refining and spent cooking oils from the food industry are suitable starting materials, these mercury‐capturing polymers can be synthesised entirely from waste and supplied on multi‐kilogram scales. This study is therefore an advance in waste valorisation and environmental chemistry.
A polymer prepared by co-polymerisation of sulfur and canola oil removed Fe3+ from water. Microwave irradiation was convenient in promoting the polymerisation.
The
triboelectric effect (TE), simply described as the generation
of electricity from tribology or friction, has been known for over
1500 years. TE arises from charge transfer between surfaces under
contact, typically attributed to electron transfer. However, emerging
understanding shows how the ion transfer and material transfer (bond
cleavage) mechanisms play a key role in TE. An engineering focus on
increasing the porosity, surface roughness, and use of heterogeneous
materials has resulted in a recent explosion in triboelectric literature,
particularly toward soft and flexible polymer devices. Here, we critically
evaluate recent progress in TE generators and link engineered performance
to the fundamental driving forces of triboelectricity using the exemplar
triboelectric polymer poly(dimethylsiloxane).
Piezoelectric polymers are emerging as exceptionally promising materials for energy harvesting.While the theoretical figures of merit for piezoelectric polymers are comparable to ceramics, the measurement techniques need to be retrofitted to account for the different mechanical properties of the softer polymeric materials. Here, how contact electrification is often mistaken for piezoelectric charge is discussed, through friction and contact separation, and a perspective for how to separate these effects is provided. The state of the literature is assessed, and recommendations are made for This article is protected by copyright. All rights reserved.clear and simple guidelines in reporting, for both sample geometry and testing methods, to enable accurate determination of piezoelectric figures of merit in polymers. Such improvements will allow an understanding of what types of material manipulation are required in order to enhance the piezoelectric output from polymers and enable the next generation of polymer energy harvester design.
Contact
electrification and the triboelectric effect are complex
processes for mechanical-to-electrical energy conversion, particularly
for highly deformable polymers. While generating relatively low power
density, contact electrification can occur at the contact–separation
interface between nearly any two polymer surfaces. This ubiquitousness
of surfaces enables contact electrification to be an important phenomenon
to understand energy conversion and harvesting applications. The mechanism
of charge generation between polymeric materials remains ambiguous,
with electron transfer, material (also known as mass) transfer, and
adsorbed chemical species transfer (including induced ionization of
water and other molecules) all being proposed as the primary source
of the measured charge. Often, all sources of charge, except electron
transfer, are dismissed in the case of triboelectric energy harvesters,
leading to the generation of the “triboelectric series”,
governed by the ability of a polymer to lose, or accept, an electron.
Here, this sole focus on electron transfer is challenged through rigorous
experiments, measuring charge density in polymer–polymer (196
polymer combinations), polymer–glass (14 polymers), and polymer–liquid
metal (14 polymers) systems. Through the investigation of these interfaces,
clear evidence of material transfer via heterolytic bond cleavage
is provided. Based on these results, a generalized model considering
the cohesive energy density of polymers as the critical parameter
for polymer contact electrification is discussed. This discussion
clearly shows that material transfer must be accounted for when discussing
the source of charge generated by polymeric mechanical energy harvesters.
Thus, a correlated physical property to understand the triboelectric
series is provided.
Piezoelectric fluoropolymers convert mechanical energy to electricity and are ideal for sustainably providing power to electronic devices. To convert mechanical energy, a net polarization must be induced in the fluoropolymer, which is currently achieved via an energy-intensive electrical poling process. Eliminating this process will enable the low-energy production of efficient energy harvesters. Here, by combining molecular dynamics simulations, piezoresponse force microscopy, and electrodynamic measurements, we reveal a hitherto unseen polarization locking phenomena of poly(vinylidene fluoride–co–trifluoroethylene) (PVDF-TrFE) perpendicular to the basal plane of two-dimensional (2D) Ti3C2Tx MXene nanosheets. This polarization locking, driven by strong electrostatic interactions enabled exceptional energy harvesting performance, with a measured piezoelectric charge coefficient, d33, of −52.0 picocoulombs per newton, significantly higher than electrically poled PVDF-TrFE (approximately −38 picocoulombs per newton). This study provides a new fundamental and low-energy input mechanism of poling fluoropolymers, which enables new levels of performance in electromechanical technologies.
High-performance, unpoled and recyclable piezoelectric generators are produced by combining dipole templating via single-walled carbon nanotubes with shear-induced polarisation via 3D printing of fluoropolymers.
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