Single-atom Pt on carbon nanotubes for selective electrocatalysis

Utilizing supported single atoms as catalysts presents an opportunity to reduce the usage of critical raw materials such as platinum,which are essential for electrochemical reactions such as hydrogen oxidation reaction(HOR).Herein,we describe the synthesis of a Pt single electrocatalyst inside single-walled carbon nanotubes(SWCNTs)via a redox reaction.Characterizations via electron microscopy,X-ray photoelectron microscopy,and X-ray absorption spectroscopy show the single-atom nature of the Pt.The electrochemical behavior of the sample to hydrogen and oxygen was investigated using the advanced floating electrode technique,which minimizes mass transport limitations and gives a thorough insight into the activity of the electrocatalyst.The single-atom samples showed higher HOR activity than state-of-the-art 30%Pt/C while almost no oxygen reduction reaction activity in the proton exchange membrane fuel cell operating range.The selective activity toward HOR arose as the main fingerprint of the catalyst confinement in the SWCNTs.

Lignocellulosic biomass as sustainable feedstock and materials for power generation and energy storage

Lignocellulosic biomass has attracted great interest in recent years for energy production due to its renewability and carbon-neutral nature.There are various ways to convert lignocellulose to gaseous,liquid and solid fuels via thermochemical,chemical or biological approaches.Typical biomass derived fuels include syngas,bio-gas,bio-oil,bioethanol and biochar,all of which could be used as fuels for furnace,engine,turbine or fuel cells.Direct biomass fuel cells mediated by various electron carriers provide a new direction of lignocellulose conversion.Various metal and non-metal based carriers have been screened for mediating the electron transfer from biomass to oxygen thus generating electricity.The power density of direct biomass fuel cells can be over 100 mW cm^(-2),which shows promise for practical applications.Lignocellulose and its isolated components,primarily cellulose and lignin,have also been paid considerable attention as sustainable carbonaceous materials for preparation of electrodes for supercapacitors,lithium-ion batteries and lithium-sulfur batteries.In this paper,we have provided a state-of-the-art review on the research progress of lignocellulosic biomass as feedstock and materials for power generation and energy storage focusing on the chemistry aspects of the processes.It was recommended that process integration should be performed to reduce the cost for thermochemical and biological conversion of lignocellulose to biofuels,while efforts should be made to increase efficiency and improve the properties for biomass fuelled fuel cells and biomass derived electrodes for energy storage.

Polar interaction of polymer host-solvent enables stable solid electrolyte interphase in composite lithium metal anodes

The lithium(Li) metal anode is an integral component in an emerging high-energy-density rechargeable battery.A composite Li anode with a three-dimensional(3 D) host exhibits unique advantages in suppressing Li dendrites and maintaining dimensional stability.However,the fundamental understanding and regulation of solid electrolyte interphase(SEI),which directly dictates the behavior of Li plating/stripping,are rarely researched in composite Li metal anodes.Herein,the interaction between a polar polymer host and solvent molecules was proposed as an emerging but effective strategy to enable a stable SEI and a uniform Li deposition in a working battery.Fluoroethylene carbonate molecules in electrolytes are enriched in the vicinity of a polar polyacrylonitrile(PAN) host due to a strong dipole-dipole interaction,resulting in a LiF-rich SEI on Li metal to improve the uniformity of Li deposition.A composite Li anode with a PAN host delivers 145 cycles compared with 90 cycles when a non-polar host is employed.Moreover,60 cycles are demonstrated in a 1:0 Ah pouch cell without external pressure.This work provides a fresh guidance for designing practical composite Li anodes by unraveling the vital role of the synergy between a 3 D host and solvent molecules for regulating a robust SEI.

Enforced Freedom: Electric-Field-Induced Declustering of Ionic-Liquid Ions in the Electrical Double Layer

Ions in the bulk of solvent-free ionic liquids bind into ion pairs and clusters.The competition between the propensity of ions to stay in a bound state,and the reduction of the energy when unbinding in electric field,determines the portion of free ions in the electrical double layer.We present the simplest possible mean-field theory to study this effect."Cracking"of ion pairs into free ions in electric field is accompanied by the change of the dielectric response of the ionic liquid.The predictions from the theory are verified and further explored by molecular dynamics simulations.A particular finding of the theory is that the differential capacitance vs potential curve displays a bell shape,despite the low concentration of free charge carriers,because the dielectric response reduces the threshold concentration for the bell-to camelshape transition.The presented theory does not take into account overscreening and oscillating charge distributions in the electrical double layer.But in spite of the simplicity of the model,its findings demonstrate a clear physical effect:a preference to be a charged monopole rather than a dipole(or higher order multipole)in strong electric field.

Acrylamide fragment inhibitors that induce unprecedented conformational distortions in enterovirus 713C and SARS-CoV-2 main protease

RNA viruses are critically dependent upon virally encoded proteases to cleave the viral polyproteins into functional proteins.Many of these proteases exhibit a similar fold and contain an essential catalytic cysteine,offering the opportunity to inhibit these enzymes with electrophilic small molecules.Here we describe the successful application of quantitative irreversible tethering(qIT)to identify acrylamide fragments that target the active site cysteine of the 3C protease(3Cpro)of Enterovirus 71,the causative agent of hand,foot and mouth disease in humans,altering the substrate binding region.Further,we re-purpose these hits towards the main protease(Mpro)of SARS-CoV-2 which shares the 3C-like fold and a similar active site.The hit fragments covalently link to the catalytic cysteine of Mpro to inhibit its activity.We demonstrate that targeting the active site cysteine of Mpro can have profound allosteric effects,distorting secondary structures to disrupt the active dimeric unit.

Nanoparticle meta-grid for enhanced light extraction from light-emitting devices

Based on a developed theory,we show that introducing a meta-grid of sub-wavelength-sized plasmonic nanoparticles(NPs)into existing semiconductor light-emitting-devices(LEDs)can lead to enhanced transmission of light across the LED-chip/encapsulant interface.This results from destructive interference between light reflected from the chip/encapsulant interface and light reflected by the NP meta-grid,which conspicuously increase the efficiency of light extraction from LEDs.The“meta-grid”,should be inserted on top of a conventional LED chip within its usual encapsulating packaging.As described by the theory,the nanoparticle composition,size,interparticle spacing,and distance from the LED-chip surface can be tailored to facilitate maximal transmission of light emitted from the chip into its encapsulating layer by reducing the Fresnel loss.The analysis shows that transmission across a typical LEDchip/encapsulant interface at the peak emission wavelength can be boosted up to ~99%,which is otherwise mere~84% at normal incidence.The scheme could provide improved transmission within the photon escape cone over the entire emission spectrum of an LED.This would benefit energy saving,in addition to increasing the lifetime of LEDs by reducing heating.Potentially,the scheme will be easy to implement and adopt into existing semiconductor-device technologies,and it can be used separately or in conjunction with other methods for mitigating the critical angle loss in LEDs.

Editorial for “Special Issue on the 2019 and 2020 iGEM proceedings”

Synthetic biology comprises engineering design principles to build biological and biomimetic devices with versatile applicability.This Special Issue is composed of contributions with roots in the 2019 and 2020 international Genetically Engineered Machine(iGEM)competitions,and present platforms that enable the implementation of SynBio to bio-medicine,bio-remediation,and bio-materials.The field of synthetic biology provides a vast and interdisciplinary engineering playground,where researchers harness a wide range of molecular building blocks and machinery to assemble devices that span from bio-engineered organisms displaying new and interesting functionalities[1]to synthetic-cell mimics able to coordinate bio-inspired behaviours[2].SynBio is thus a versatile and comprehensive toolkit for novel technologies with a unique potential for societal impact.