Electrochemical Regeneration of Highly Stable and Sustainable Cellulose/Graphene Adsorbent Saturated with Dissolved Organic Dye

Electrochemical regeneration of adsorbents presents a cost-effective and environmentally friendly approach. Yet, its application to 3D structured adsorbents such as cellulose/graphene-based aerogels remains largely unexplored. This study introduces a method for producing these aerogels, highlighting their significant adsorption capacity for dissolved organic pollutants and resilience during electrochemical regeneration. By adjusting the ratio of hydrophobized cellulose nanofibers to graphene, the aerogels demonstrate a tunable adsorption capacity, ranging from 56 to 228 mg/g. Hydrophobization using oleic acid is vital for maintaining the aerogels’ structural stability in water. Notably, the aerogels maintain structural integrity and efficiency over at least 18 electrochemical regeneration cycles, underscoring their potential for long-term environmental applications. The increase in adsorption capacity observed after regeneration cycles, approximately 10–20% by the fifth cycle, is attributed to electrochemical surface roughening and the creation of new adsorption sites. The tunability and durability of these aerogels offer a sustainable solution for adsorption with electrochemical regeneration technology

Electrochemical Regeneration of Highly Stable and Sustainable Cellulose/Graphene Adsorbent Saturated with Dissolved Organic Dye

Electrochemical regeneration of adsorbents presents a cost-effective and environmentally friendly approach. Yet, its application to 3D structured adsorbents such as cellulose/graphene-based aerogels remains largely unexplored. This study introduces a method for producing these aerogels, highlighting their significant adsorption capacity for dissolved organic pollutants and resilience during electrochemical regeneration. By adjusting the ratio of hydrophobized cellulose nanofibers to graphene, the aerogels demonstrate a tunable adsorption capacity, ranging from 56 to 228 mg/g. Hydrophobization using oleic acid is vital for maintaining the aerogels’ structural stability in water. Notably, the aerogels maintain structural integrity and efficiency over at least 18 electrochemical regeneration cycles, underscoring their potential for long-term environmental applications. The increase in adsorption capacity observed after regeneration cycles, approximately 10–20% by the fifth cycle, is attributed to electrochemical surface roughening and the creation of new adsorption sites. The tunability and durability of these aerogels offer a sustainable solution for adsorption with electrochemical regeneration technology

Electrochemical Regeneration of Highly Stable and Sustainable Cellulose/Graphene Adsorbent Saturated with Dissolved Organic Dye

Electrochemical regeneration of adsorbents presents a cost-effective and environmentally friendly approach. Yet, its application to 3D structured adsorbents such as cellulose/graphene-based aerogels remains largely unexplored. This study introduces a method for producing these aerogels, highlighting their significant adsorption capacity for dissolved organic pollutants and resilience during electrochemical regeneration. By adjusting the ratio of hydrophobized cellulose nanofibers to graphene, the aerogels demonstrate a tunable adsorption capacity, ranging from 56 to 228 mg/g. Hydrophobization using oleic acid is vital for maintaining the aerogels’ structural stability in water. Notably, the aerogels maintain structural integrity and efficiency over at least 18 electrochemical regeneration cycles, underscoring their potential for long-term environmental applications. The increase in adsorption capacity observed after regeneration cycles, approximately 10–20% by the fifth cycle, is attributed to electrochemical surface roughening and the creation of new adsorption sites. The tunability and durability of these aerogels offer a sustainable solution for adsorption with electrochemical regeneration technology

Electrocatalytic Activity of Functionalized Carbon Paper Electrodes and Their Correlation to the Fermi Level Derived from Raman Spectra

Carbon paper electrodes are employed for different electrochemical applications such as flow batteries and fuel cells. However, redox reactions such as VO2+/VO2+ in a vanadium redox flow battery have been found to possess relatively slow kinetics, resulting in significant activation losses during operation. In this work, we demonstrate a facile and scalable method for nitrogen doping of carbon paper electrodes, leading to superior electrocatalytic activity. The effects of pyrolytic pretreatments under different conditions on the performance of carbon paper were also studied to elucidate their electrocatalytic activity from a material physics perspective, using Raman spectroscopy. The 2D Raman signature, a specific feature of the carbon structures, was employed to understand the effect of different pretreatments on the Fermi level of the carbon papers, which could help us elucidate their intrinsic electron transfer kinetics. The full wave half-maximum of the 2D Raman band and the intensity ratio I2D/IG were used to indicate changes in the Fermi level relative to the untreated carbon paper, and hence the electrocatalytic properties, which were confirmed using voltammetric techniques. Although heating of carbon paper in air at around 500 °C (a widely used method for activating carbon paper electrodes) increases the surface area by about 16 times compared to untreated and nitrogen-doped carbon paper, the latter exhibits superior electrocatalytic property for VO2+/VO2+, [Fe­(CN)6]3–/4–, and the oxygen reduction reaction. This study provides greater physical insights into different pretreatments in terms of the energy barrier at the interface, which will aid the pursuit for better carbon-based electrode materials and provide mechanistic details about charge transfer processes at the interface

Mechanistic Insight into Electrode Processes by Operando Visualization of Interfacial pH Using Fluorescent Nanosensors

Operando visualization of interfacial pH is crucial, yet challenging in electrochemical processes. Herein, we report the fabrication and utilization of ratiometric, fluorescent pH-sensitive nanosensors for operando quantification of fast-dynamic, interfacial pH changes in electrochemical processes and environments where unprotected fluorescent dyes would be degraded. Spatio-temporal pH changes were detected using an electrochemically coupled laser scanning confocal microscope (EC-LSCM) during the electrocoagulation treatment of model and field samples of oil-sands-produced water. Operando visualization of interfacial pH provided new insights into the electrode processes, including ion speciation, electrode fouling, and Faradaic efficiency. We provide compelling evidence that formed metal complexes precipitate at the edge of the pH boundary layer and that there is a strong coupling between the thickness of the interfacial pH layer and the electrode fouling. Furthermore, these findings provide a powerful pathway for optimizing the operating conditions, minimizing electrode passivation, and enhancing the efficiency of electrochemical processes, e.g., electrocoagulation, flow batteries, capacitive deionization, and electrolyzes

Mechanistic Insight into Electrode Processes by Operando Visualization of Interfacial pH Using Fluorescent Nanosensors

Operando visualization of interfacial pH is crucial, yet challenging in electrochemical processes. Herein, we report the fabrication and utilization of ratiometric, fluorescent pH-sensitive nanosensors for operando quantification of fast-dynamic, interfacial pH changes in electrochemical processes and environments where unprotected fluorescent dyes would be degraded. Spatio-temporal pH changes were detected using an electrochemically coupled laser scanning confocal microscope (EC-LSCM) during the electrocoagulation treatment of model and field samples of oil-sands-produced water. Operando visualization of interfacial pH provided new insights into the electrode processes, including ion speciation, electrode fouling, and Faradaic efficiency. We provide compelling evidence that formed metal complexes precipitate at the edge of the pH boundary layer and that there is a strong coupling between the thickness of the interfacial pH layer and the electrode fouling. Furthermore, these findings provide a powerful pathway for optimizing the operating conditions, minimizing electrode passivation, and enhancing the efficiency of electrochemical processes, e.g., electrocoagulation, flow batteries, capacitive deionization, and electrolyzes

Mechanistic Insight into Electrode Processes by Operando Visualization of Interfacial pH Using Fluorescent Nanosensors

Operando visualization of interfacial pH is crucial, yet challenging in electrochemical processes. Herein, we report the fabrication and utilization of ratiometric, fluorescent pH-sensitive nanosensors for operando quantification of fast-dynamic, interfacial pH changes in electrochemical processes and environments where unprotected fluorescent dyes would be degraded. Spatio-temporal pH changes were detected using an electrochemically coupled laser scanning confocal microscope (EC-LSCM) during the electrocoagulation treatment of model and field samples of oil-sands-produced water. Operando visualization of interfacial pH provided new insights into the electrode processes, including ion speciation, electrode fouling, and Faradaic efficiency. We provide compelling evidence that formed metal complexes precipitate at the edge of the pH boundary layer and that there is a strong coupling between the thickness of the interfacial pH layer and the electrode fouling. Furthermore, these findings provide a powerful pathway for optimizing the operating conditions, minimizing electrode passivation, and enhancing the efficiency of electrochemical processes, e.g., electrocoagulation, flow batteries, capacitive deionization, and electrolyzes

Mechanistic Insight into Electrode Processes by Operando Visualization of Interfacial pH Using Fluorescent Nanosensors

Operando visualization of interfacial pH is crucial, yet challenging in electrochemical processes. Herein, we report the fabrication and utilization of ratiometric, fluorescent pH-sensitive nanosensors for operando quantification of fast-dynamic, interfacial pH changes in electrochemical processes and environments where unprotected fluorescent dyes would be degraded. Spatio-temporal pH changes were detected using an electrochemically coupled laser scanning confocal microscope (EC-LSCM) during the electrocoagulation treatment of model and field samples of oil-sands-produced water. Operando visualization of interfacial pH provided new insights into the electrode processes, including ion speciation, electrode fouling, and Faradaic efficiency. We provide compelling evidence that formed metal complexes precipitate at the edge of the pH boundary layer and that there is a strong coupling between the thickness of the interfacial pH layer and the electrode fouling. Furthermore, these findings provide a powerful pathway for optimizing the operating conditions, minimizing electrode passivation, and enhancing the efficiency of electrochemical processes, e.g., electrocoagulation, flow batteries, capacitive deionization, and electrolyzes

Hydrodynamic Study of Ion Transfer at the Liquid/Liquid Interface: the Channel Flow Cell

A hydrodynamic system based on the channel flow cell for voltammetric detection of ions at the liquid/liquid interface is reported. The current response for tetraethylammonium ion transfer across a membrane-supported liquid/liquid interface is shown to be consistent with existing theory for both the flow rate and voltage scan rate dependence of such processes, with no calibration factors or other adjustable parameters required. The analytical utility of such a device is discussed with specific regard to in situ measurements in flow systems

Influence of Flow Field Design on Zinc Deposition and Performance in a Zinc-Iodide Flow Battery

Among the aqueous redox flow battery systems, redox chemistries using a zinc negative electrode have a relatively high energy density, but the potential of achieving high power density and long cycle life is hindered by dendrite growth at the anode. In this study, a new cell design with a narrow gap between electrode and membrane was applied in a zinc-iodide flow battery. In this design, some of the electrolyte flows over the electrode surface and a fraction of the flow passes through the porous felt electrode in the direction of current flow. The flow battery was tested under constant current density over 40 cycles, and the efficiency, discharge energy density, and power density of the battery were significantly improved compared to conventional flow field designs. The power density obtained in this study is one of the highest power densities reported for the zinc-iodide battery. The morphology of the zinc deposition was studied using scanning electron microscopy and optical profilometry. It was found that the flow through the electrode led to a thinner zinc deposit with lower roughness on the surface of the electrode, in comparison to the case where there was no flow through the electrode. In addition, inhibition of dendrite formation enabled operation at a higher range of current density. Ex situ tomographic measurements were used to image the zinc deposited on the surface and inside the porous felt. Volume rendering of graphite felt from X-ray computed tomography images showed that in the presence of flow through the electrode, more zinc deposition occurred inside the porous felt, resulting in a compact and thinner surface deposit, which may enable higher battery capacity and improved performance