Flexible solid-state supercapacitors (FSSCs) are frontrunners in energy storage device technology and have attracted extensive attention owing to recent significant breakthroughs in modern wearable electronics In this study, we review the state-of-the-art advancements in FSSCs to provide new insights on mechanisms, emerging electrode materials, flexible gel electrolytes and novel cell designs The review begins with a brief introduction on the fundamental understanding of charge storage mechanisms based on the structural properties of electrode materials The next sections briefly summarise the latest progress in flexible electrodes (ie, freestanding and substrate-supported, including textile, paper, metal foil/wire and polymer-based substrates) and flexible gel electrolytes (ie, aqueous, organic, ionic liquids and redox-active gels) Subsequently, a comprehensive summary of FSSC cell designs introduces some emerging electrode materials, including MXenes, metal nitrides, metal–organic frameworks (MOFs), polyoxometalates (POMs) and black phosphorus Some potential practical applications, such as the development of piezoelectric, photo-, shape-memory, self-healing, electrochromic and integrated sensor-supercapacitors are also discussed The final section highlights current challenges and future perspectives on research in this thriving field

Towards flexible solid-state supercapacitors for smart and wearable electronics

Biological cell template synthesis of nitrogen-doped porous hollow carbon spheres/MnO2 composites for high-performance asymmetric supercapacitors

The solid-liquid interface reaction between phosphate rock (PR) and metals (Pb, Cu, and Zn) was studied. Phosphate rock has the highest affinity for Pb, followed by Cu and Zn, with sorption capacities of 138, 114, and 83.2 mmol/kg PR, respectively. In the Pb-Cu-Zn ternary system, competitive metal sorption occurred with sorption capacity reduction of 15.2%, 48.3%, and 75.6% for Pb, Cu, and Zn, respectively compared to the mono-metal systems. A fractional factorial design showed the interfering effect in the order of Pb>Cu>Zn. Desorption of Cu and Zn was sensitive to pH change, increasing with pH decline, whereas Pb desorption was decreased with a strongly acidic TCLP extracting solution (pH = 2.93). The greatest stability of Pb retention by PR can be attributed to the formation of insoluble fluoropyromorphite [Pb(10)(PO(4))(6)F(2)], which was primarily responsible for Pb immobilization (up to 78.3%), with less contribution from the surface adsorption or complexation (21.7%), compared to 74.5% for Cu and 95.7% for Zn. Solution pH reduction during metal retention and flow calorimetry analysis both supported the hypothesis of retention of Pb, Cu, and Zn by surface adsorption or complexation. Flow calorimetry indicated that Pb and Cu adsorption onto PR was exothermic, while Zn sorption was endothermic. Our research demonstrated that PR can effectively remove Pb from solutions, even in the presence of other heavy metals (e.g. Cu, Zn).

https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1014&context=ersc_fac

Understanding the Mechanisms of Lead, Copper, and Zinc Retention by Phosphate Rock

The movement of drops in electric fields plays a role in processes as diverse as storm cloud formation, ink-jet printing and lab-on-a-chip manipulations. An important factor in practical applications is the tendency for adjacent drops to coalesce, usually assumed to be favoured if drops are oppositely charged and attracted to each other. Now Ristenpart et al. show that when oppositely charged drops move towards each other in an electric field whose strength exceeds a critical value, the drops simply 'bounce' off one another. This observation calls for a re-evaluation of our understanding of all processes involving electrically induced drop motion. Adjacent drops of fluid coalesce, and oppositely charged drops have long been assumed to experience an attractive force that favours their coalescence. However, here it is observed that oppositely charged drops moving towards each other in a strong electric field do not coalesce when the field strength exceeds a certain value but rather 'bounce' off one another. This observation calls for a re-evaluation of our understanding of processes such as storm cloud formation and ink-jet printing, which involve electrically induced droplet motion. Electric fields induce motion in many fluid systems, including polymer melts1, surfactant micelles2 and colloidal suspensions3. Likewise, electric fields can be used to move liquid drops4. Electrically induced droplet motion manifests itself in processes as diverse as storm cloud formation5, commercial ink-jet printing6, petroleum and vegetable oil dehydration7, electrospray ionization for use in mass spectrometry8, electrowetting9 and lab-on-a-chip manipulations10. An important issue in practical applications is the tendency for adjacent drops to coalesce, and oppositely charged drops have long been assumed to experience an attractive force that favours their coalescence11,12,13. Here we report the existence of a critical field strength above which oppositely charged drops do not coalesce. We observe that appropriately positioned and oppositely charged drops migrate towards one another in an applied electric field; but whereas the drops coalesce as expected at low field strengths, they are repelled from one another after contact at higher field strengths. Qualitatively, the drops appear to ‘bounce’ off one another. We directly image the transient formation of a meniscus bridge between the bouncing drops, and propose that this temporary bridge is unstable with respect to capillary pressure when it forms in an electric field exceeding a critical strength. The observation of oppositely charged drops bouncing rather than coalescing in strong electric fields should affect our understanding of any process involving charged liquid drops, including de-emulsification, electrospray ionization and atmospheric conduction.

http://absimage.aps.org/image/DFD09/MWS_DFD09-2009-001564.pdf

Non-coalescence of oppositely charged drops

In this work, an Euler–Euler multiphase CFD model is proposed for continuous fast pyrolysis of biomass in a fluidized-bed reactor. In the model, a lumped, multi-component, multi-stage kinetic model is applied to describe the pyrolysis of a biomass particle. Variable particle porosity is used to account for the evolution of the particle's physical properties. Biomass is modeled as a composite of three reference components: cellulose, hemicellulose, and lignin. Pyrolysis products are categorized into three groups: gas, tar vapor (bio-oil), and solid char. The particle kinetic processes and their interactions with the reactive gas phase are modeled with a multi-fluid description derived from the kinetic theory of granular flows. A time-splitting approach is applied to decouple the convection and reaction calculations using a synchronized time step. The CFD model is employed to study the fast pyrolysis of both cellulose and bagasse in a lab-scale fluidized-bed reactor. The dynamics, particle heating, reaction of the biomass phase, char formation, elutriation, and spatial distribution of tar and gas inside the reactor are investigated. The yields of tar, gas, and char are also discussed.

/pdf/a-cfd-model-for-biomass-fast-pyrolysis-in-fluidized-bed-3v18n78a94.pdf

A CFD model for biomass fast pyrolysis in fluidized-bed reactors

Hierarchical porous carbon from hazardous waste oily sludge for all-solid-state flexible supercapacitor

Experimental study on catalytic pyrolysis of oil sludge under mild temperature.

Oil sludge (OS) pyrolysis was conducted with a tube furnace reactor. Production distributions and compositions were investigated under different conditions of pyrolysis temperature, heating mode, and atmosphere (N2/CO2). Little change was detected with the product yields of char, oil, and gas when the final temperature exceeded 600 °C. Compared with slow pyrolysis, oil and char yields decreased and gas yield increased in fast pyrolysis. CO2 could promote OS pyrolysis, resulting in a reduction of char yield. SEM images showed that the surface of OS was smooth with a dense texture while the surface of OS char was rough with a well-developed pore structure that formed after pyrolysis. Simulated distillation results showed that light fractions from OS pyrolysis were more than 30% higher than those of oil from OS extraction. With the increase of pyrolysis temperature, light fractions (gasoline, diesel, and jet fuel) in pyrolysis oil decreased. During fast pyrolysis, the heavy fractions produced can be cracked ...

Experimental Study on Pyrolysis Characteristics of Oil Sludge with a Tube Furnace Reactor

A TG-MS study on the coupled pyrolysis and combustion of oil sludge

Integrated thermal treatment of OS is a promising method for massive and effective treatment of the waste. The present work investigated the tank OS pyrolysis by a thermogravimetric analyzer and a tube furnace reactor. Pyrolysis char combustion performance was studied with the thermogravimetric analyzer. Results showed that OS pyrolysis mainly occurred between 200 °C and 700 °C. With the increase of pyrolysis temperature, char yield decreased while gas yield increased. When pyrolysis temperature exceeded 600 °C, the oil yield decreased. Simulated distillation showed that oil products properties barely changed when pyrolysis temperature exceeded 600 °C. Light fractions (gasoline and diesel) from OS pyrolysis were more than 28% higher than those of oil from OS extraction. Major components of pyrolysis gas include H2, CO, CO2, and hydrocarbons (CHS). CHS content was more than 40% in the pyrolysis gas in all cases. The molar H/C ratio and O/C ratio were lower for OS chars from higher temperature pyrolysis. The surface of OS char was rough with a well-developed pore structure formed during pyrolysis, which was conducive to the combustion reaction. The combustion characteristic of OS char from higher temperature pyrolysis was poorer than that of OS char from lower pyrolysis temperature, resulting from the less volatile content and more carbon crystal degree for OS char from higher temperature pyrolysis. With well-developed pore structure, relative simple composition, good ignition and burnout characteristics, OS char could perform well in actual combustion in CFB boilers.

Zhenbo Wang

Papers

Hierarchical porous carbon from hazardous waste oily sludge for all-solid-state flexible supercapacitor

Experimental study on catalytic pyrolysis of oil sludge under mild temperature.

Experimental Study on Pyrolysis Characteristics of Oil Sludge with a Tube Furnace Reactor

A TG-MS study on the coupled pyrolysis and combustion of oil sludge

Study on pyrolysis characteristics of tank oil sludge and pyrolysis char combustion