An efficient oxygen reduction reaction (ORR) is crucial for deoxygenation electrolyzers. However, the use of metal catalysts in electrolyzer designs is challenging due to their high cost, catalyst dissolution, and susceptibility to poisoning. Conductive polymers have emerged as a promising new class of metal-free catalysts for ORR, combining electron conductivity and a lack of an insulating oxidation layer. In this study, a new n-type polymer is explored, poly(benzimidazobenzophenanthroline) (BBL), as an ORR catalyst to enhance deoxygenation efficiency in carbon-based electrolyzers. Electrocatalytic studies show that BBL film improves ORR kinetics via a four-electron pathway with a mass activity of the order of 100 A g-1. A low-voltage electrolyzer is constructed and tested using BBL-coated carbon fiber paper (CFP) as the cathode for ORR and CFP as the anode to drive the oxidation of catechol as a compensating faradaic reaction to facilitate ORR. The deoxygenation electrolyzer with a drop-cast BBL cathode achieves fast deoxygenation kinetics, reaching below 0.1 mg L-1 DO in salty solution with 0.001 m catechol. The findings introduce a new approach to deoxygenating thermal fluids by employing an ORR polymer catalyst and a compensating redox additive (RA) in water.

Lignin, a central renewable carbon resource in the biosphere, has recently emerged as a promising redox-active material for organic batteries. Currently, the main challenge lies in finding a form of lignin that combines water-based processability with good cyclic stability, as the two industrially common forms, kraft lignin and lignosulfonate, each offers only one of these advantages. In this work, we demonstrate that lignin nanoparticles (LNPs) act as redox-active centers that are insoluble but exhibit colloidal stability in aqueous media, allowing for straightforward processing into electrodes for zinc-ion batteries. Electrodes based on conductive composites of LNPs with poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) were shown electrochemically to achieve specific capacities reaching 42.5 mAh/g at a current density of 1 A/g. A zinc-ion battery prototype using this composite demonstrated a specific energy of 54 Wh/kg, outperforming previous lignin-based energy storage devices. This zinc-lignin battery exhibited excellent Coulombic efficiency of around 100%, with a specific capacity of 82.5 mAh/g at 0.05 A/g and a capacity retention of approximately 61% after 2000 charge/discharge cycles. Our results highlight the potential of LNPs in advancing eco-friendly, cost-effective, and high-performance lignin-based energy storage devices.

Electrocatalysis enables the industrial transition to sustainable production of chemicals using abundant precursors and electricity from renewable sources. De-centralized production of hydrogen peroxide (H2O2) from water and oxygen of air is highly desirable for daily life and industry. We report an effective electrochemical refinery (e-refinery) for H2O2 by means of electrocatalysis-controlled comproportionation reaction (2(H)O + O -> 2(HO)), feeding pure water and oxygen only. Mesoporous nickel (II) oxide (NiO) was used as electrocatalyst for oxygen evolution reaction (OER), producing oxygen at the anode. Conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) drove the oxygen reduction reaction (ORR), forming H2O2 on the cathode. The reactions were evaluated in both half-cell and device configurations. The performance of the H2O2 e-refinery, assembled on anion-exchange solid electrolyte and fed with pure water, was limited by the unbalanced ionic transport. Optimization of the operation conditions allowed a conversion efficiency of 80%.

The two-electron oxygen reduction reaction (ORR), powered by affordable renewable energy, presents a more promising and sustainable approach to hydrogen peroxide production than traditional methods. In this study, we introduce a membrane electrolyzer for ORR-to-H2O2 generation. The conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) acts as the cathode that aids the oxygen reduction reaction through a two-electron pathway to produce H2O2. At the anode, we employed the oxidation of a model organic molecule, 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt monohydrate (tiron). This catalyst-free anode process, as an alternative to the sluggish water oxidation reaction commonly used in classical electrolyzers, reduces voltage loss to release protons, cross the membrane, and feed the ORR at the cathode. Our study investigated the often-neglected issue of organic crossover during electrolyzer operation and its significant impact on transport behavior. This research paves the way for the development of crossover-free flow cells, extending the realm of electrochemical devices based on the electrolyte fed and the membrane. We introduce a membrane electrolyzer for the generation of hydrogen peroxide via oxygen reduction and catalyst-free oxidation of quinones. The study reports the effect of the applied coulombic forces on ions, which is the origin of crossover.

The redox-diffusion (RD) battery concept introduces an environmentally friendly solution for stretchable batteries in autonomous wearable electronics. By utilising plant-based redox-active biomolecules and cellulose fibers for the electrode scaffold, separator membrane, and current collector, along with a biodegradable elastomer encapsulation, the battery design overcomes the reliance on unsustainable transition metal-based active materials and non-biodegradable elastomers used in existing stretchable batteries. Importantly, it addresses the drawback of limited attainable battery capacity, where increasing the active material loading often leads to thicker and stiffer electrodes with poor mechanical properties. The concept decouples the active material loading from the mechanical structure of the electrode, enabling high mass loadings, while retaining a skin-like young's modulus and stretchability. A stretchable ion-selective membrane facilitates the RD process, allowing two separate redox couples, while preventing crossovers. This results in a high-capacity battery cell that is both electrochemically and mechanically stable, engineered from sustainable plant-based materials. Notably, the battery components are biodegradable at the end of their life, addressing concerns of e-waste and resource depletion. A stretchable battery design that uses sustainable plant-based materials and enables high electrochemical and mechanical performance and is biodegradable at the end-of-life.

Ionic thermoelectric materials can generate large thermal voltages under temperature gradients while also being low-cost and environmentally friendly. Many electrolytes with large Seebeck coefficients are reported in recent years, however, the mechanism of the thermal voltage is remained elusive. In this work, three types of polyelectrolytes are studied with different cations and identified a significant contribution to their thermal voltage originating from a concentration gradient. This conclusion is based on studies of the loss and gain of water upon temperature changes, variations in conductivity with water content and temperature, and the voltages induced by changes in water content. The results are analyzed by the "hopping mode" dynamics of charge transport in electrolytes. The hydration of different cations influences the water concentration gradient, which affects the barrier height and ion-induced potential in the electrodes. This work shows that the hydro-voltage in ionic thermoelectric devices can be one order of magnitude larger than the contribution from thermodiffusion-induced potentials, and becomes the main contributor to energy harvesting when implemented into ionic thermoelectric supercapacitors. Together with the rationalized theoretical discussion, this work clarifies the mechanism of thermal voltages in electrolytes and provides a new path for the development of ionic thermoelectric materials. The thermal voltage of polyelectrolyte films largely depends on the water concentration gradient under a temperature difference, which can be optimized to promote the generated total voltage up to over 30 mV K-1.image

Ice formation detection is important in telecommunications and aeronautics, e.g., ice on the wings of an aircraft affects its aerodynamic performance and leads to fatal accidents. While many types of sensors exist, resistive sensors for ice detection have been poorly explored. They are however attractive because of their simplicity and the possibility to install an array of sensors on large areas to map the ice formation on wings. Hygroscopic ionic conductors have been demonstrated for resistive ice sensing but their high resistance prevents the readout of sensor arrays. In this work, mixed ionic-electronic polymer conductors (MIEC) are considered for the first time for ice detection. The polymer blend poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is solution deposited on a pair of electrodes. The sensor displays an abrupt rise in electrical resistance during the transition phase between water liquid to solid. It is proposed that the morphology and electronic transport in PEDOT are affected by the freezing event because the absorbed water in the PSS-rich phase undergoes dilatation upon forming ice crystals. For the aeronautics application, successful tests of integration of sensing layer in pre-preg layers of aeronautical grade and freezing detection are carried out to validate the ice detection principle.

Desalination by capacitive deionization (CDI) is a promising technique to combine desalination and energy storage. The efficiency of charge storage process, which is equivalent to the desalination process, depends strongly on the presence of Faradic side reactions on the electrode. Herein, the performance of a new low-cost designed flow-through electrode with porous carbon nanoparticles (CP) coating on carbon-fiber paper (CFP) is evaluated. The CP layer enables high capacitance while the CFP core makes fluid dynamics along and across the electrode. The electrodes are evaluated by studying the effective operational CDI parameters, such as operational voltage, degassing of electrolyte, and salt concentration. The Faradic side reaction and its effect on charge efficiency (CE) are evaluated which are estimated to decrease to 46% by liquid flow bringing dissolved oxygen from the air-electrolyte interface to the electrode. The CE enhances to 59% with a salt concentration of 1 m. By purging N-2 gas, CE is much higher (>85%) with a maximum efficiency of 97% at 0.6 V. Three regimes of the complex kinetic of side reactions are found involving various species such as O-2, H2O2, H-2, and carbon oxidation and the implication of those regimes for real applications are discussed.

We propose a simple and low-cost flow-through electrode for electrochemical cells used for instance in capacitive desalination. We have coated macro-porous carbon fiber papers with various loads of carbon microporous particles to combine both a high surface area and an open structure for good fluid dynamics. In this first study, we restrict our investigation to the charging/discharging behavior, the identification of side reactions, and the effect of geometry on the diffusion of ions. The electrochemical performance was first investigated by cyclic voltammetry and galvanic charge-discharge techniques. The specific capacitance increases by three orders of magnitude upon adding the carbon particles. Then, electrochemical impedance spectroscopy revealed the presence of charge transfer phenomena and modification in the mass transport by the diffusion process for the coated electrode.

Hydrogen technology, as a future breakthrough for the energy industry, has been defined as an environmentally friendly, renewable, and high-power energy carrier. The green production of hydrogen, which mainly relies on electrocatalysts, is limited by the high cost and/ or the performance of the catalytic system. Recently, studies have been conducted in search of bifunctional electrocatalysts accelerating both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR). Herein, we report the investigation of the high efficiency bifunctional electrocatalyst TaS2 for both the HER and the HOR along with the asymmetric effect of inhibition by organic intercalation. The linear organic agent, to boost the electron donor property and to ease the process of intercalation, provides a higher interlayer gap in the tandem structure of utilized nanosheets. XRD and XPS data reveal an increase in the interlayer distance of 22%. The HER and the HOR were characterized in a Pt group metal-free electrochemical system. The pristine sample shows a low overpotential of -0.016 Vat the onset. The intercalated sample demonstrates a large shift in its performance for the HER. It is revealed that the intercalation is a potential key strategy for tuning the performance of this family of catalysts. The inhibition of the HER by intercalation is considered as the increase in the operational window of a water-based electrolyte on a negative electrode, which is relevant to technologies of electrochemical energy storage.