3D Electrode Research Articles

Demonstration of Fast Simultaneous Neutron and X-Ray Tomography for Fuel Cell Water Content Measurements

Neutron radiography has been a powerful tool for measuring water content within operating fuel cells. The resolution for neutron imaging has been steadily improving and has demonstrated the ability to measure water content in industrially relevant catalyst layers. The difficulty in measuring catalyst layer or interfacial water content with neutron radiography is that the method assumes that the layers of the MEA are flat and uniform with no variation which is a poor assumption. To combat this assumption, it is necessary to move to neutron tomography that resolves the fuel cell in three dimensions. Combining neutron tomography with simultaneous X-ray tomography improves layer and interface identification which facilitates better water saturation measurements. In addition to capturing the “waviness” of the MEA, this method can be applied to tracking water distribution in structured 3D electrodes. This talk will demonstrate current developments in fast simultaneous neutron and X-ray tomography, methods to improve saturation calculations within the various porous layers, and showcase new hardware developments available to the NIST user community.

(Keynote) Reversible CO2 Reduction Electrocatalysis in Solar-Powered Chemistry

Semi-artificial photosynthesis interfaces biological catalysts with synthetic materials such as electrodes or light absorbers to overcome limitations in natural and artificial photosynthesis. The benefit of using biocatalysts in electrocatalytic CO2 reduction is their electrochemical reversibility that enables their operation at very low overpotentials with high selectivity. This presentation will summarise my research group’s progress in integrating the CO2 reducing enzyme formate dehydrogenase into bespoke hierarchical 3D electrode scaffolds and the exploitation in solar-powered catalysis. I will present the electrochemical features and characterisation of the biocatalyst-material interface and provide my team's understanding of the electrochemical properties of the immobilised formate dehydrogenase. This insight allows the wiring of the biocatalyst into electrocatalytic schemes, photoelectrochemical devices and photocatalytic systems for unique CO2 utilisation reactions. The fundamental insights gained by integrating isolated formate dehydrogenase in electrodes will be presented and the case be made that this enzyme allows opening a solar-to-chemical conversion space that is currently not accessible with purly synthetic or biological catalysts (see uploaded Image as example).Recent publications: (1) Lam et al., Angew. Chem. Int. Ed., 2023, in print. (2) Bhattacharjee et al., Nat. Synth., 2023, 2, 182-92. (3) Badiani et al., J. Am. Chem. Soc., 2022, 144, 14207-16. (4) Cobb et al., Nat. Chem., 2022, 14, 417-24. (5) Edwardes Moore et al., Proc. Natl. Acad. Sci. USA, 2022, 119, e2114097199. (6) Anton Garcia et al., Nat. Synth. 2022, 1, 77-86.Reviews: (1) Fang et al., Chem. Soc. Rev., 2020, 49, 4926–52. (2) Zhang & Reisner, Nature Rev. Chem., 2020, 4, 6–21. (3) Kornienko et al., Acc. Chem. Res., 2019, 52, 1439–44. (4) Kornienko et al., Nature Nanotech., 2018, 13, 890–99

A Green and Fluorine‐Free Fabrication of 3D Self‐Supporting MXene by Combining Anodic Electrochemical In Situ Etching with Cathodic Electrophoretic Deposition for Electrocatalytic Hydrogen Evolution

AbstractThe work presents a green and fluorine‐free environmentally friendly two‐electrode system, which enables the direct fabrication of the corresponding 3D MXene electrodes by the synergistic combination of anodic electrochemical in situ Al etching from Mo2TiAlC2 MAX and cathodic electrophoretic deposition. In just several minutes, the Mo2TiC2 MXene can be deposited on the cathode plate (Pt foil or carbon cloth) without the need for organic large‐molecule intercalation agents or ultrasound treatment. This approach allows an efficient separation of MXene from the electrolyte, leading to a significant reduction in the quantity of waste acid generated by conventional acid etching processes. The electrochemically etched‐MXene can be uniformly and stably deposited onto carbon cloth (E‐MXene@CC), enabling its direct utilization as a 3D electrocatalyst for hydrogen evolution reaction (HER). This unique 3D E‐MXene@CC exhibits a moderate HER performance and outperforms most of the reported pure non‐precious MXene‐based catalysts in 0.5 m H2SO4. In order to clarify the catalytic mechanism, in situ Raman spectroscopy of 3D E‐MXene@CC reveals a significant down‐shift without observing any new bands when the HER potential shifts negatively, which can be attributed to H+ intercalation.

Enhanced Ion Transport Through Mesopores Engineered with Additional Adsorption of Layered Double Hydroxides Array in Alkaline Flow Batteries.

Efficient mass transfer in electrodes is essential for the electrochemical processes of battery charge and discharge, especially at high rates and capacities. This study introduces a 3D electrode design featuring layered double hydroxides (LDHs) nanosheets array grown in situ on a carbon felt surface for flow batteries. The mesoporous structure and surface characteristic of LDH nanosheets, especially, the hydroxyl groups forming a unique "H-bonding-like" geometry with ferrous cyanide ions, facilitate efficient adsorption and ion transport. Thus, the designed LDHs electrode enables the alkaline zinc-iron flow battery to maintain a voltage efficiency of 81.6% at an ultra-high current density of 320mA cm-2, surpassing the values reported in previous studies. The energy efficiency remains above 84% after 375 cycles at a current density of 240mA cm-2. Molecular dynamics simulations verify the enhanced adsorption effect of LDH materials on active ions, thus facilitating ion transport in the battery. This study provides a novel approach to improve mass transport in electrodes for alkaline flow batteries and other energy storage devices.

Nitrogen-doped oxygen-rich porous carbon framework towards aqueous zinc ion hybrid capacitors and zinc-iodine batteries

Zinc ion hybrid capacitors (ZIHCs) and zinc-iodine batteries (ZIBs) have attracted significant attention as promising components for large-scale energy storage owing to their excellent security, environmental friendness and high theoretical capacity of Zn anode. However, there still exist some respective obstacles for commercial applications, such as limited specific capacity, poor cycling stability of ZIHCs or shuttle effect of polyiodide of ZIBs. Here, to enhance electrochemical properties, we report a synergistic one-step activation strategy using KMnO4 and Zn(NO3)2 for nitrogen-doped oxygen-rich three-dimensional hierarchical porous carbon (NOPC). Benefiting from its high specific surface area, three-dimensional porous morphology and improved redox sites from heteroatom doping, the as obtained NOPC exhibits desired electrochemical performance as cathode for ZIHCs and ZIBs. The NOPC-based electrode achieves an ultra-high specific capacity of 230 mAh g−1 at 0.1 A g−1, and 118 mAh g−1 can be maintained at 10 A g−1. Besides, a distinguished energy density of 213.0 Wh kg−1 and a high-power density of 11.2 kW kg−1 are also achieved with a constructed ZIHCs device. Furthermore, the NOPC/I2 composite exhibited excellent rate performance (54 mAh g−1 at 10 A g−1) and cycling performance (∼88.3 % retention upon 5000 cycles) in ZIBs device. This work provides a facile but effective strategy to develop 3D porous electrodes for ZIHCs and ZIBs with remarkable rate and cycling performance.

Diffusion kinetics of ionic charge carriers across Ti3C2Tx MXene-aqueous electrochemical interfaces

Titanium carbide MXene -Ti3C2Tx - is a representative and well-employed electrode material for a variety of electrochemical energy storage applications. Despite exhibiting metal-like electronic conductivity, restacked Ti3C2Tx films show mediocre rate performance. Here, we report on the estimation of diffusion coefficients of aqueous cations (H+, Li+, Na+and Ca+2) across Ti3C2Tx MXene interlayer spaces by employing electrochemical impedance spectroscopy. Proton diffusivity across 2D slits is found to be 2.2 * 10−8 ± 0.4 * 10−8 cm2/s, which is three orders of magnitude slower than in bulk water. Such a sluggish diffusive behavior is attributed to interfacial confinement effects in the 2D space. It is found that protons diffuse three times faster than hydrated metal cations (Li+, Na+and Ca+2) through Ti3C2Tx slits and exhibit strong potential dependent behavior. Therefore, the rate performance of Ti3C2Tx MXene electrodes is limited by the ionic transportation in the 2D slits rather than electronic transport. This study provides insights into the engineering of open 2D electrode architectures for better ionic diffusive pathways towards the design of high rate MXene based energy storage devices.

Three-dimension porous Zn-Cu alloy: An inexpensive electrocatalyst for highly selective CO2 reduction to CO in non-aqueous electrolyte

Designing cheap and highly active electrochemical CO2 reduction (ECO2R) systems are crucial for their commercial applications. Herein, we report a 3D porous Zn-Cu alloy electrode for ECO2R to CO. A small amount of Cu has a dramatic effect on the micro-morphology of the electrode. Furthermore, DFT calculations confirm that Zn-Cu alloying significantly reduces the formation energy barrier of *CO intermediates. The synergy between the unique 3D porous structure and the alloying effect enables the Cu0.3Zn9.7 electrode to achieve up to 90.69 % Faraday efficiency (FE) for CO at −1.2 V (vs. reversible hydrogen electrode (RHE)). Furthermore, we prepare a novel non-aqueous cathode electrolyte consisting of deep eutectic solvent (DES) and propylene carbonate (PC) for ECO2R. The FECO of Cu0.3Zn9.7 increased to 94.89 % and the reduction potential decreased to −1 V (vs. RHE). The low cost of preparing 3D porous electrodes and the ease of synthesizing the novel non-aqueous electrolyte render this ECO2R system for CO promising for large-scale application.

MOFs-derived 3D porous ZnCo2O4 nanocubes intercalated 3D graphene electrode for Superior lifespan hybrid supercapacitors.

MOFs-derived 3D porous ZnCo2O4 nanocubes intercalated 3D graphene electrode for Superior lifespan hybrid supercapacitors.

Tip-Enhanced Sub-Femtomolar Steroid Immunosensing via Micropyramidal Flexible Conducting Polymer Electrodes for At-Home Monitoring of Salivary Sex Hormones.

Noninvasive testing and continuous monitoring of ultralow-concentration hormones in biofluids have attracted increasing interest for health management and personalized medicine, in which saliva could fulfill the demand. Steroid sex hormones such as progesterone (P4) and β-estradiol (E2) are crucial for female wellness and reproduction; however, their concentrations in saliva can vary down to sub-pM and constantly fluctuate over several orders of magnitude. This remains a major obstacle toward user-friendly and reliable monitoring at home with low-cost flexible biosensors. Herein we introduce a 3D micropyramidal electrode architecture to address such challenges and achieve an ultrasensitive flexible electrochemical immunosensor with sub-fM-level detection capability of salivary sex hormones within a few minutes. This is enabled by micropyramidal electrode arrays consisting of a poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) thin film as the coating layer and electrochemically decorated gold nanoparticles (AuNPs) to improve the antibody immobilization. The enhanced mass transport around the 3D tips provided by the micropyramidal architecture is discovered to improve the detection limit by 3 orders of magnitude, pushing it to as low as ∼100 aM for P4 and ∼20 aM for E2, along with a wide linear range up to μM. Accordingly, these hormones down to sub-fM in >1000-fold-diluted saliva samples can be accurately measured by the printed soft immunosensors, thus allowing at-home testing through simple saliva dilution to minimize the interfering substances instead of centrifugation. Finally, monitoring of the female ovarian hormone cycle of both P4 and E2 is successfully demonstrated based on the centrifuge-free saliva testing during a period of 4 weeks. This ultrasensitive and soft 3D microarchitected electrode design is believed to provide a universal platform for a diverse variety of applications spanning from accurate clinical diagnostics and counselling and in vivo detection of bioactive species to environmental and food quality tracing.

Fabrication of a 3D structure MnO2 electrode with high MnO2 mass loading as the cathode for high-performance aqueous zinc-ion batteries

Benefiting from the remarkable advantages (eco-friendly, cost-effective, and high safety) of rechargeable aqueous zinc-ion batteries (AZIBs), AZIBs are regarded as viable alternatives to traditional Lithium-ion batteries (LIBs). However, in prevailing research, the excellent electrochemical performance usually achieved by ultra-low active material loadings (e.g., <1 mg/cm²), which is far from the active material mass loading of commercial electrodes in practical (≥10 mg/cm²). Balancing superior properties with high mass loading has posed a challenge. To surmount this, an innovative method combined ultrasonic processing, freeze-drying, and 3D printing technologies is used to engineer a high MnO2 mass loading cathode for AZIBs (3D cathode). Notably, the grid structure of 3D cathode substantially augmenting the surface area for redox reactions during charge/discharge processes, which greatly enhanced the pseudo-capacitance process of cathode. Additionally, the uniform and stable microstructure exhibited the dual capability of expediting ion/electron transfer and sustaining the structural integrity throughout charge/discharge cycles. Consequently, the 3D cathode demonstrated superior comprehensive electrochemical properties at the MnO2 high mass loading of 10 mg/cm2 (138.7 mAh/g at 1 A/g, 87.4 mAh/g after 500 cycles, 82 % energy efficiency) and 15 mg/cm2 (113.3 mAh/g at 1 A/g, 56.3 mAh/g after 400 cycles, 81 % energy efficiency).

In-situ engineering of 3D porous Co nanoparticles incorporated in B/N Co-doped carbon nanotube/nanofiber networks as integrated cathode materials for Zn-air batteries

Rational design and construction of low-cost and highly efficient bifunctional catalysts toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for the commercialization of the rechargeable Zn-air batteries (ZABs). Herein, a 3D self-standing bifunctional catalytic electrode has been successfully achieved by in-situ confinement of Co nanoparticles into B/N co-doped carbon nanotube/nanofiber well-integrated networks (Co-B/N-CNTs@CFs). The purpose of designing such a 3D network structure is to optimize the electronic structure of the active sites for high electrocatalytic activity, ensure continuous and fast electron and charge transfer for high utilization of active sites, and avoid the abscission and aggregation of nanocatalysts for high electrocatalytic stability, which is confirmed by a series of experimental, characterization, and theoretical studies. As a result, the Co-B/N-CNTs@CFs as integrated cathode materials deliver efficient and stable OER/ORR performance with a ΔE of 0.59 V, largely outperforming the benchmark Pt/C-RuO2 electrode (0.71 V), and hence leading to appealing applications in both the assembled aqueous and flexible solid-state ZABs. This study forges a new path for the production of integrated cathode while enhancing their superiority, allowing for the construction of energy storage devices.

Durability over 11 days in electrocatalytic hydrogen evolution reaction via designing a 3D magnetic electrode and regulating the electronic structure

Most catalysts used for the hydrogen evolution reaction (HER) possess superior electrocatalysis activities but suffer from poor stability, hampering their applications in the electrolysis industry. Here, we fabricated three magnetic electrodes: “H2-catalyst-I” (NiCoFeP@F-NiCoAlFe-LDHs@NiCoFe), “H2-catalyst-II” NiCoFeP@F-NiCoAlFe-LDHs@NiCoFe and NiCoFe), and “H2-catalyst-III” (H2-catalyst-I@poly(3,4-ethylene dioxythiophene) (PEDOT)), to study the effect of magnet field on the electrocatalysis life of NiCo-based phosphides. Among them, the magnetic H2-catalyst-II electrode demonstrates extended stability over 10 days due to the protection effect of NiCoFe alloy powders under a magnetic field, surpassing that of the magnetic H2-catalyst-I electrode. The magnetic H2-catalyst-III electrode exhibits enhanced HER behaviors (η10 = 106 mV, a little Tafel slope of 79 mV·dec-1, and durability for up to 11 days). This stability can be attributed to its strong electron structure nature due to both the magnetic field and the PEDOT coating layer. Finally, an electrolytic cell is assembled by applying the magnetic H2-catalyst-III cathode and F-doped NiCoAl-LDHs@ZnFeAl-LDHs/NF anode and displays the electrocatalysis life over 10 days. In conclusion, the magnetic field holds a beneficial effect on strengthening the electron structure of the catalyst, thereby extending the lifespan of HER, which introduces a new approach for designing and preparing robust HER catalysts to meet the demands in the electrolysis water industry.

Decoupling of Reaction Overpotentials and Ionic Transport Losses within 3D Porous Electrodes in Zero-Gap Alkaline Electrolysis Cells

Designing more efficient and productive alkaline electrolysis (AE) cells requires the development of electrode microstructures that facilitate mass transport and reduce associated ionic transport losses within the electrodes. Here we propose a method, relying on a minimum of three reference electrodes, that allows to decouple the Galvani potential losses (GL) associated with ionic migration within each of the electrodes from the overall electrode overpotential. This provides additional insight along with the separation of the voltage losses within the anode, cathode, and separator that is also achieved during zero-gap operation at industrially relevant conditions. Different Nickel electrode structures have been investigated to assess the effect of thickness, surface area, and porosity on the GL within the electrodes. The GL in the anode are higher than in the cathode for the same electrode structure and decrease upon decreasing electrode thickness. Reducing the cathode thickness, while maintaining the same specific surface area, improves performance more compared to the anode. Moreover, electrodes with large pore diameter (0.43 mm) were observed to facilitate the oxygen evolution reaction (OER), whereas electrodes with small pore diameter (0.23 mm) and large surface area are beneficial for the hydrogen evolution reaction (HER). Overall, the proposed methodology provides vital information in guiding the microstructural optimization of electrodes for advanced alkaline electrolysis cells.

3D Electrode architecture of high surface area carbon-sulfur composite as high energy density cathode for lithium-sulfur battery

High-performance lithium-sulfur (Li-S) battery is a potential candidate for next-generation energy storage systems to mitigate the ever-rising energy demand. The low cost of sulfur, eco-friendliness, and high energy density compared to the emerging LIBs (450 Wh kg−1 for Li-S batteries vs. 150–250 Wh kg−1 for LIBs) inspires the research on Li–S technology. In this work, carbon fiber-based free-standing electrodes are fabricated using a high surface area carbon-sulfur (HSAC-S) composite synthesized by the melt-diffusion method. The porous carbon host facilitates high sulfur loading in the void spaces and benefits the electrolyte infiltration and Li-ion diffusivity. Electrochemistry reveals that HSAC-S@CF exhibits an enhanced discharge capacity of 1000 mAh g−1 (750 mAh g−1 for HSAC-S@Al) in the 2nd cycle and maintains 620 mAh g−1 capacity till the 100th cycle. In comparison, HSAC-S@Al delivers 350 mAh g−1 capacity at the 80th cycle at a current density of 100 mA g−1. Besides, at 200 mA g−1, the free-standing electrode HSAC-S@CF delivers an initial capacity of 600 mAh g−1 (498 mAh g−1 HSAC-S@Al) and retains 497 mAh g−1 till the 100th cycle with 83 % capacity retention (60 % HSAC-S@Al). HSAC-S@CF displays good C-rate performance at a higher current density of 1 A g−1 (408 mAh g−1) and 1.5 A g−1 (346 mAh g−1). The conductive CF backbone provides mechanical stability, accommodates volume changes, and reduces particle agglomeration. The internal void spaces of the CF matrix act as a reservoir for polysulfides and minimize the shuttling effect. This work represents an effective cathode modification approach to understand the impact of high surface area carbon additives on free-standing 3D electrode architecture and its interaction with sulfur for improving the capacity and cycling stability in Li-S batteries.

Bridging the Gap: Electrode Microstructure and Interphase Characterization by Combining ToF‐SIMS and Machine Learning

AbstractThis article presents a new analytical methodology to analyze large (hundreds of µm) battery electrode microstructures by mapping the spatial distribution of the main phases (e.g., active material and carbon‐binder domain) and degradation products (solid‐ or cathode‐electrolyte interphase) formed during cycling. The methodology can be used for a better understanding of the relationships between electrode architecture and degradation, paving the way toward the analysis of interphases spatial distribution and their correlations to the electrode formulation, microstructure, and cycling conditions. This work is based on time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), and focuses on analyzing large 2D electrode cross‐sections at both the microstructure and single particle/agglomerate level. It also shows that this analysis can be expanded to 3D electrode microstructures when combining ToF‐SIMS and devoted machine learning procedures, which can be of particular interest to the 3D electrochemical modeling community.

Multifunctional 3D electrodes for tunable high-performance hybrid zinc batteries

The high energy density and long cycling life of zinc-based batteries are restricted by the single electrochemical reaction system. To improve the electrochemical performance of batteries, electrode materials, electrolytes and membranes are regularly modified, while the construction of battery systems is often neglected. Herein, a multifunctional electrode was prepared via 3D printing, which successfully coupled the metal oxide/hydroxide-zinc battery (MZB) reaction and rechargeable zinc-air battery (RZAB) reaction. The ultrathick hierarchical 3D electrode provided a tunable capacity for the MZB system, which enabled the possibility for feasible output regulation of this hybrid system. The active material NiCoLDH was discovered to undergo structure reconstruction during cycling, which revealed the capacity fading mechanism. The delicate system design and discovery ensured a high-performance battery configuration and revealed the corresponding mechanism, opening a new avenue for developing high-performance zinc batteries.

Structural Electronic Skin for Conformal Tactile Sensing.

The conformal integration of the electronic skin on the non-developable surface is in great demand for the comprehensive tactile sensing of robotics and prosthetics. However, the current techniques still encounter obstacles in achieving conformal integration of film-like electronic skin on non-developable surfaces with substantial curvatures for contact pressure detection and tactile mapping. In this paper, by utilizing the 3D printing technology to prepare the 3D electrode array in the structural component following its surface curvature, and covering it with a molded functional shell to form the pressure sensitive iontronic interface, a device is proposed to achieve high-sensitive pressure detection and high-fidelity tactile mapping on a complicated non-developable surface, called structural electronic skin (SES). The SES is prepared in a 3D printed fingertip with 46 tactile sensing units distributed on its curved surface, achieving the integration of both structural and tactile functions in a single component. By integrating the smart fingertip into a dexterous hand, a series of demonstrations are presented to show the dead-zone free pressure detection and tactile mapping with high sensitivity, for instance, 2D pulse wave monitoring and robotic injection in a medical robot, object recognition and compliant control in a smart prosthesis.

Direct Ink Writing 3D Printing for High-Performance Electrochemical Energy Storage Devices: A Minireview.

Despite tremendous efforts that have been dedicated to high-performance electrochemical energy storage devices (EESDs), traditional electrode fabrication processes still face the daunting challenge of limited energy/power density or compromised mechanical compliance. 3D thick electrodes can maximize the utilization of z-axis space to enhance the energy density of EESDs but still suffer from limitations in terms of poor mechanical stability and sluggish electron/ion transport. Direct ink writing (DIW), an eminent branch of 3D printing technology, has gained popularity in the manufacture of 3D electrodes with intricately designed architectures and rationally regulated porosity, promoting a triple boost in areal mass loading, ion diffusion kinetics, and mechanical flexibility. This focus review highlights the fundamentals of printable inks and typical configurations of 3D-printed devices. In particular, preparation strategies for high-performance and multifunctional 3D-printed EESDs are systemically discussed and classified according to performance evaluation metrics such as high areal energy density, high power density, high volumetric energy density, and mechanical flexibility. Challenges and prospects for the fabrication of high-performance 3D-printed EESDs are outlined, aiming to provide valuable insights into this thriving field.

Long-term stability and toxicity effects of three-dimensional electrokinetic remediation on chromium-contaminated soils

The three-dimensional electrokinetic remediation (3D EKR) achieved efficient removal of chromium (Cr) from the soil through mechanisms including electromigration, electroosmosis, and redox reactions. In this study, the long-term stability, leaching toxicity, bioavailability, and phytotoxicity of Cr in remediated soils were systematically analyzed to comprehensively evaluate the effectiveness of the 3D EKR method. The results showed that the concentration of hexavalent chromium (Cr (VI)) in the leachate of the 3D EKR system with sulfidated nano-scale zerovalent iron (S-nZVI) was more than 40% lower than those of the other 3D electrode groups, and the time required to reach the level III standard of groundwater quality criterion in China (0.05 mg/L, GB/T 14848-2017) was significantly shortened. The stabilization of Cr(VI) in contaminated soil after 3D EKR was maintained for 300 pore volumes (PVs), indicating that the treated Cr(VI) had good long-term stability. The leaching toxicity and bioaccessibility of Cr were assessed by the synthetic precipitation leaching procedure (SPLP), the toxicity characteristic leaching procedure (TCLP), and the physiologically based extraction test (PBET). The concentration of Cr(VI) in the SPLP, TCLP, and PBET leachates of the S-nZVI group decreased by more than 25% compared to the other 3D electrode groups, corresponding to the decrease in leaching toxicity and bioavailability of the treated Cr during the 15-day remediation period. In addition, the germination rate of wheat seeds and the average biomass of wheat seedlings in the S-nZVI group under alkaline conditions (EE) were higher than those in the non-polluting group (Blank-OH), indicating that the remediated soil had no obvious toxicity to wheat. In summary, 3D EKR achieved a satisfactory and stable remediation effect on Cr-contaminated soil, especially when using S-nZVI as the 3D electrode.

A three-dimensional in-situ self-electrolysis system based on Ni3(HITP)2/graphene-based composite aerogel particle electrodes for efficient deep removal of phenol from coking wastewater

Herein, a Ni3(HITP)2/graphene-based composite aerogel (Ni3(HITP)2/GA) particle electrode is developed for the oxidation removal of phenol with three-dimensional electrode technology. The as-constructed three-dimensional electrode system possesses high in-situ self-electrolysis capacity and achieves highly efficient degradation of phenol, completely removed within 15 min with a decomposition rate constant of 0.3283 min−1. Ni3(HITP)2 in Ni3(HITP)2/GA and the tetradentate Ni–N2O2 coordination bond generated at the composite interface produce H2O2 highly selectively via the 2e- ORR pathway. The graphene layer converts H2O2 into •OH by using the 1e- of Ni3(HITP)2 excitation and the microelectrode action of the particle electrode. Furthermore, the simultaneous generation of •OH and O2•- in the system greatly reduces the dependence on acidic environment and broadens the scope of utilization. The present work provides a new strategy for the efficient construction of particle electrodes in 3D electrode systems, which allows their potential application in the purification of coking wastewater.