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Maritime transport generates substantial amounts of carbon emissions and particulate matter (PM 2.5) particles waste, which is considered as abundant industrial waste. This study presents repurposing the PM as an anode for Li and Na-ion batteries. Structure and morphology properties of the PM particles were characterized with Raman spectroscopy, energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and scanning electron microscopy, respectively. Cyclic voltammetry analysis at various rates indicated a pseudocapacitive charge storage mechanism in the annealed PM electrode, with diffusive contributions dominating at lower scan rates. This study provides insight for waste valorization by repurposing of PM particles from heavy fuel oil into electrochemical energy storage applications. 

In this study, we aim to repurpose diesel soot emissions from maritime ships as carbonaceous anode material for Na-ion batteries. Diesel soot, also known as particulate matter, is considered an air pollutant, which is formed due to the incomplete combustion of diesel fuel and emitted in exhaust streams into the surrounding atmosphere. Due to diesel particulate filters working in tandem with diesel engines, soot accumulation can have negative impacts on the engine operation and needs to be removed, which subsequently creates an abundant waste product with no direct use.^1,2In air, particulate matter is a significant hindrance to human health, as larger particles exacerbate respiratory conditions while ultrafine particles can be absorbed into the blood, leading to cardiovascular, autoimmune, and carcinogenic disease in the body.^3,4Previous research in using soot as an anodic material has made annealing treatment a cornerstone in the application of waste carbon in battery systems.^1,5,6 In exploring applications of diesel soot in energy systems, we collect particulate matter emissions from a cruise ship, ball mill the soot and anneal the material at a temperature of 650℃. The composite electrode is then prepared by mixing annealed or unannealed particulate matter and PVDF polymer additive in an 8.5:1.5 mass ratio. Using a coin cell setup, we use the particulate matter electrode and Na metal as working and counter electrodes, with an electrolyte of 1M NaPF6 in PC. Electrochemical performance was tested with cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. Electrochemical behavior illustrates significant gains with annealing treatment, in tandem with SEI development after initial cycling, promoting ion diffusivity and stable columbic efficiency after development. Further analysis of the charge storage mechanism revealed that the diesel soot stores charge pseudo-capacitively, where diffusive mechanisms tend to dominate at lower scan rates. Acknowledgment:This work is supported by the National Science Foundation (award number 2344722). 

Cetyltrimethylammonium bromide (CTAB) has been used to enhance the selectivity of CO2 electrochemical reduction. Traditionally, this selectivity was attributed to repulsion of water molecules due to a CTAB self-assembled monolayer, which forms under negative potential and disassembles at positive voltage due to electrostatic repulsions. In this report, using in operando interface sensitivity sum frequency generation spectroscopy, we investigated the self-assembly behavior of CTAB across a broad electrochemical potential range. We observed that CTAB molecules form a stable monolayer at the Stern layer over the entire potential scan, even when the electrodes are positively charged. Rather than disassembling, the CTAB molecules reorient themselves to balance the electrostatic interactions and the non-covalent hydrophobic effects, the latter being the primary driving force maintaining the monolayer at a positive potential. This finding contrasts the traditional view that CTAB monolayers are absent when the electrodes are positively charged, indicating a stable and ordered monolayer with respect to the electrostatic repulsions at liquid/electrode interfaces. The balance between non-covalent and electrostatic interactions offers a facile and reversible electrochemical method to control the local environment and dominating interactions at the Stern layer of the electrode surface, thus providing a means for engineering a micro-electrochemical environment. 

Becauseof thehighdielectricstrengthofwater, it isextremelydifficult todischargeplasmainacontrollablewayin the aqueous phase. By using lithographically defined electrodes andmetal/dielectric nanoparticles, we create electric field enhancementthatenablesplasmadischargeinliquidelectrolytesatsignificantlyreducedappliedvoltages.Here,weusehighvoltage (10−30kV)nanosecondpulse(20ns)dischargestogenerateatransientplasmaintheaqueousphase.Anelectrodegeometrywitha radiusofcurvatureofapproximately10μm,agapdistanceof300μm,andanestimatedfieldstrengthof5×106V/cmresultedina reductionintheplasmadischargethresholdfrom28to23kV.Asecondstructurehadaradiusofcurvatureofaround5μmanda gapdistanceof100μmhadanestimatedfieldstrengthof9×106V/cmbutdidnotperformaswellasthelargergapelectrodes. Addinggoldnanoparticles(20nmdiameter) insolutionfurther reducedthethresholdforplasmadischargeto17kVduetothe electricfieldenhancementatthewater/goldinterface,withanestimatedE-fieldenhancementof4×.Addingaluminananoparticles decoratedwithPtreducedtheplasmadischargethresholdto14kV. Inthisscenario, theemergenceofatriplepointatthejuncture ofalumina,Pt,andwaterresultsinthecoexistenceofthreedistinctdielectricconstantsatasingularlocation.Thisleadstoanotable concentrationof electric field, effectively aiding in the initiationof plasma discharge at a reduced voltage. To gain amore comprehensive and detailed understanding of the electric field enhancement mechanism, we performed rigorous numerical simulations.Thesesimulationsprovidevaluableinsights intotheintricateinterplaybetweenthelithographicallydefinedelectrodes, thenanoparticles, andthe resultingelectricfielddistribution, enablingus toextract crucial informationandoptimize thedesign parameters forenhancedperformance.