High Oxygen Evolution Potential Research Articles

Electrocatalysis degradation of biochemical tail water from coking wastewater using particle electrode with persulphate

ABSTRACT Due to the intricate composition and recalcitrant nature of coking wastewater, the biochemical effluent often fails to meet standards. This study explored the preparation of particle electrodes, utilizing activated carbon powder (PAC) loading single-element Fe, Co, and Ni, as well as dual-element Ni–Fe and Co–Fe as catalyst. The particle electrode system was integrated with persulphate (PS) activation to enhance its performance. The effects of potassium persulphate (KPS) dosages, currents, and Ni:Fe ratios were investigated. The results showed that bimetallic particle electrodes outperformed their monometallic particle electrodes. Among the five electrode materials, Ni–Fe/PAC achieved the best degradation efficiency of 84.4% and the lowest energy consumption of 19.73 kW·h·kg−1 COD. When the initial concentrations of TOC and COD were set at 300 and 280 mg L−1, the Ni–Fe/PAC with 5 mmol L−1 KPS achieved removal efficiencies of 61.7 and 84.4%, respectively. The metals on Ni/PAC and Co/PAC existed in the zero-valent state, while Fe on Fe/PAC was present as Fe2O3. Co–Fe/PAC exhibited the formation of CoFe2O4 oxides. Ni–Fe/PAC possessed the lowest hydrogen evolution reaction potential (−0.28 V), and the highest oxygen evolution potential (2.4 V), and reached an electrochemical active surface area (ECSA) of 236.3 cm2. Cyclic voltammetry (CV) curves indicated that the direct redox reactions and indirect oxidation of pollutants occurred concurrently. Both •OH and ⋅ SO 4 − radicals played crucial roles during the degradation processes. The degradation efficiency of organic matter was as follows: benzene compounds (88.4%) >heterocyclic compounds (75.3%) >polycyclic aromatic hydrocarbons (53.9%).

Synergistic modification of Ti/PbO2 electrodes with metal ions (Nd, Al, Bi) and STAB surfactant for electrocatalytic treatment of desulfurization wastewater

In this study, PbO2 electrodes are modified by co-doping with different metallic elements (Nd, Al, Bi) and stearyl trimethyl ammonium bromide (STAB) using the electrodeposition method. The modified electrodes, designated as Ti/PbO2-Nd-STAB, Ti/PbO2-Al-STAB, and Ti/PbO2-Bi-STAB, are then applied in the electrochemical degradation of desulfurization wastewater. The surface morphology, crystal structure, and elemental valence of the prepared electrodes are analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Their electrochemical performance and stability are assessed by linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and accelerated life testing (ALT). The results reveal that modification with metallic elements and STAB significantly enhances the physicochemical and electrocatalytic performance of the Ti/PbO2 electrode. Among the modified electrodes, the Ti/PbO2-Nd-STAB electrode exhibits the most compact and homogeneous surface morphology, the highest oxygen evolution potential (OEP, 2.33 V vs. SCE), the lowest chlorine evolution potential (CEP, 1.44 V vs. SCE), the largest electrochemically active surface area, the lowest charge transfer resistance, the highest electrochemical stability, and a prolonged accelerated life (65 h, which is 17 h longer than that of the unmodified electrode). Further, the optimal electrochemical oxidation process parameters for desulfurization wastewater are determined as follows: current density = 50 mA/cm2, temperature = 35 ℃, electrode spacing = 3.0 cm, and stirring rate = 300 rpm. After 300 min of electrolysis, the Ti/PbO2-Nd-STAB electrode achieves a Cl− removal rate of 86.9 % and a chemical oxygen demand (COD) removal rate of 71.2 %. After 10 cycles, the Cl− and COD removal rates decrease by 2.8 % and 1.8 %, respectively. Besides, Tafel curve analysis indicates that the chlorine evolution reaction follows the Volmer-Tafel mechanism, with the recombination of adsorbed Cl− ions on the surface oxidation film being the rate-determining step. Overall, the Ti/PbO2-Nd-STAB anode exhibits immense application potential in the treatment of desulfurization wastewater.

Unique role of Mn(II) in enhancing electro-oxidation of organic pollutants on anodes with low oxygen evolution potential at low current density

This study systematically explored the role of Mn(II) in the removal of 4-chlorophenol (4-CP) by electro-oxidation (EO) employing anodes with low oxygen evolution potential (OEP), i.e., Ti/RuO2-IrO2, Ti/Pt, and Ti/Ti4O7, as well as anodes with high OEP, namely, Ti/PbO2, Ti/SnO2, and boron-doped diamond (Si/BDD). Mn(II) significantly promoted 4-CP removal on the anodes with low OEP at fairly low current density (0.04 to 1 mA/cm2), but had minimal to negative impact on those with high OEP. Cyclic voltammetry and X-ray photoelectron spectra revealed that Mn(II) was oxidized to Mn(III), then to Mn(IV) on the anodes with low OEP, whereas its was oxidized directly to Mn(IV) on those with high OEP. Deposition of manganese oxide on the anodes with low OEP suppressed oxygen evolution reaction (OER) in EO process, but enhanced OER on those with high OEP. Quenching and spectral results consistently indicated that Mn(III) and Mn(IV) were the primary species responsible for enhancing 4-CP removal on the anodes with low OEP. These findings provide mechanistic insights into the redox transformation of Mn(II) in EO and the theoretical basis for a novel strategy to boost pollutant degradation in EO systems using low OEP anodes through coupling with the redox chemistry of manganese.

Three-dimensional porous SiC/BDD electrode with long-term robustness and enhanced electrochemical degradation performance for refractory organic pollutants

Boron-doped diamond (BDD) electrodes with a three-dimensional (3D) porous network structure can overcome the mass transfer limitations and increase substantially the utilization rate of active oxygen species. Nonetheless, the 3D porous network structure was invariably built using metallic substrates, which inherently have inferior stability because of their non-corrosion resistance and the severe thermal mismatch between BDD films and substrates. Herein, we reported, for the first time, the use of a commercially porous silicon carbide (SiC) as the substrate to construct a 3D SiC/BDD electrode to simultaneously alleviate the problematics of substrate corrosion and thermal mismatch. This novel electrode exhibited a long-term service lifetime of 800 h in 3 M H2SO4 under the current density of 50 mA cm−2, over 500 times longer than the conventional metallic substrate-based BDD electrodes. The optimum p-SiC/BDD electrode exhibited a high oxygen evolution potential of 2.04 V vs. SHE, a low charge transfer resistance of 18.4 Ω, a high mass transfer coefficient of 2.78 × 10−5 m s−1, and a thin diffusion layer thickness of 25.2 μm. The proposed electrode had a threefold larger pseudo-first-order reaction rate constant than a flat BDD electrode, although it consumed just a fourth of the latter’s electric energy. The superior performance was attributable to an increased mass transfer rate confirmed by computational fluid dynamics (CFD) simulations as well as a high yield of reactive oxygen species verified by electron spin resonance (ESR). Furthermore, the proposed SiC/BDD electrode could work effectively under different water matrices in the presence of diverse salt electrolytes, thus paving a new avenue for the structure design of robust non-active anode materials.

Fabrication of Ti/Zr-SnO2/PbO2-Nd Electrode for Efficient Electrocatalytic Degradation of Alizarine Yellow R

Introduction: A novel attempt to degrade alizarine yellow R (AYR) by lead dioxide (PbO2)/ neodymium (Nd) coated Ti anode was investigated. Method: Ti/Zr-SnO2/PbO2-Nd electrode showed high oxygen evolution potential, high current density, and neutral conditions, which favored the degradation of AYR. The PbO2-Nd layer on Ti/Zr-SnO2 was further characterized by scanning electron microscopy, and X-ray diffraction analysis, and X-ray photoelectron spectroscopy. The electrochemical properties of Ti/Zr- SnO2/PbO2-Nd electrode were evaluated by cyclic voltammetry, AC impedance spectroscopy, and accelerated life test. Result: The relatively higher oxygen evolution overpotential (~1.80 V) of the developed electrode can effectively suppress the occurrence of surface side reactions and oxygen evolution. A relatively lower charge transfer resistance (Rct, 18.0 Ω) of Ti/Zr-SnO2/PbO2-Nd electrode could be found. The Ti/Zr-SnO2/PbO2-Nd electrode exhibited an accelerated lifetime of 110 min under a very high current density of 10,000 A/m2. The doping of Nd could produce loosely-stacked sheet-like structures, thus, the number of active sites on the electrode surface increases. Conclusion: Moreover, an outstanding conductivity of Ti/Zr-SnO2/PbO2-Nd electrode was obtained, which favored the electron transfer and catalytic activity of the modified electrode. The Ti/Zr-SnO2/PbO2-Nd electrode exhibited improved electrochemical performances and higher oxygen evolution potential, and the highest oxygen evolution potential is 1.80 V. Under the current density of 30 mA/cm2, the electrocatalytic degradation of 92.3% could be achieved in 180 min. The electrochemical oxidation of AYR at the Ti/Zr-SnO2/PbO2-Nd electrode proved to be feasible and effective, indicating that it might be used for the elimination of AYR from wastewater. conclusion: The electrochemical oxidation of AYR at the Ti/Zr-SnO2/PbO2-Nd electrode proved to be feasible and effective, indicating that it might be used for the elimination of AYR from wastewater.

Efficient degradation of organics via sodium p-styrene sulfonate modified PbO2 electrode: The role of boosting electrocatalytic performance

In this work, Sodium p-styrene sulfonate (SSS)/PbO2 electrode was successfully prepared and further applied for the electrocatalytic degradation of methyl blue (MB). 95.8 % of methylene blue degradation via PbO2 electrodes was observed at the optimized conditions (100 mg/L of MB solution, current density of 30 mA·cm−2, pH=5, 180 min). When compared with PbO2 electrodes, SSS/PbO2 electrode was found to possess most effective electrocatalytic activity due to its higher oxygen evolution potential, lower charge transfer resistance, and longer service lifetime. When the concentration of SSS increases to 2vt.%, the grain size of PbO2 decreases from 21.79 nm to 19.42 nm, and the degradation rate of MB was enhanced for 5 %. Besides, the degradation rate of SSS/PbO2 electrode remained 86 % after 10 cycles, indicating that the stability and catalytic activity of the electrode were improved when the PbO2 was decorated by SSS. Moreover, the law of degradation of MB catalyzed by SSS/PbO2 electrode follows the first order kinetics. Furthermore, the energy consumption and mineralization efficiency of the SSS/PbO2 electrode were 68.73 kWh· L-1 and 4.39 %, respectively. Finally, a possible mechanism was proposed, which was further uncovered by DFT calculations.

Unravelling the efficacy of pencil graphite anode decorated with PdCu@γ-Fe2O3 nanoparticles in the electro-oxidation of amoxicillin: Insights into kinetics, oxidative pathways and toxicity evaluation

Indiscriminate use of antibiotics has resulted in the occurrence of antibiotic residues in sediments, water bodies and industrial sewage, causing ill effects on aquatic organisms and humans. Electrochemical oxidation process via in-situ generation of strong oxidant •OH is the promising method for the removal of pollutants. In this work, PdCu/γ-Fe2O3 NPs electrodeposited pencil graphite electrode (PdCu/γ-Fe2O3@PGE) has been projected as a cost-effective anode for electro-oxidation of amoxicillin (AMX), while bare PGE was used as a cathode to generate H2O2. The electrochemical measurements showed that PdCu/γ-Fe2O3 @PGE exhibited lower ΔEp (0.191 V), high electrochemical active surface area (ECSA) (0.4620 cm2), higher oxygen evolution potential (OEP) (1.72 V), and lower charge transfer resistance of 9.747 Ω/ cm2 which was ideal for electro-oxidation of AMX. Under the optimum reaction conditions (I = 0.2 mA, pH = 4), the % AMX removal reached 90.5 % after 50 min of electro-oxidation in 0.5 M NaCl. •OH, H2O2, and HOCl were found to be the in-situ generated oxidants. The AMX solution after electro-oxidation did not exhibit antibacterial activity. The toxicity of the formed intermediates were evaluated using Toxicity Estimation Software Tool (T.E.S.T) and found to be less toxic. The electrical energy consumption was estimated to be 0.786 kWhm−3.Thus, modified PGE finds application in the remediation of effluents containing amoxicillin.

Selective recovery of lithium from spent LiFePO4 powders with electrochemical method

In recent years, with the flourishing of new energy vehicles, the lithium iron phosphate (LFP) batteries are vigorously developed due to their low cost and high stability. Meanwhile, it leads to an increase in large-scale retirement of batteries. Therefore, it is crucial to develop a green and efficient recycling method. In this work, an indirect electrochemical oxidation has been proposed for selective leaching of Li ions. An electrochemical system using boron-doped diamond electrode (BDD) with high oxygen evolution potential as anode and RuO2/Ti as cathode has been built to generate oxidizing species and enhance the oxidative reaction contact for an indirect oxidation of LFP. The operating conditions were optimized to a current density of 110 mA/cm2, Na2SO4 electrolyte concentration of 0.225 M, pH of 1.7, solid–liquid ratio of 16 g/L. The leaching efficiency of Li ions reached up to 95.53 % and the leaching efficiency of Fe ions was less than 0.01 % at room temperature. A purity of lithium carbonate product of 99.93 % was obtained after precipitation of the leaching solution. This proposed method could realize efficient and rapid selective leaching of Li and Fe ions by indirect oxidation, realizing selective leaching and significantly reducing the usage of acid.

Fabrication and characterizations of a novel Ce modified PbO2 electrode with Ti4O7-rGO as the middle layer for degradation of ceftazidime

Developing stable and high-performance electrodes for effective removal of antibiotics from wastewater remains a significant challenge. Herein, a novel Ce-doped PbO2 electrode with Ti4O7-reduced graphene oxide as the middle layer (Ti/Ti4O7-rGO/Ce-PbO2) was fabricated through drop-coating and electrodeposition for the electrocatalytic degradation of ceftazidime (CAZ). The prepared Ti/Ti4O7-rGO/Ce-PbO2 electrode exhibited more active sites, higher oxygen evolution potential, and stronger ability for hydroxyl radical (•OH) generation. In the degradation experiments, approximately 100 % of CAZ (30 mg L−1) was degraded by the Ti/Ti4O7-rGO/Ce-PbO2 electrode at 40 mA cm−2 in 0.1 M Na2SO4 solution within 90 min. The quenching test and EPR analysis indicated that the •OH played a pivotal role in the degradation process. A possible degradation mechanism of CAZ, which involved bond breaking, decarboxylation, demethylation, oxidization, and ring-opening, was proposed. The Escherichia coli inhibition experiment showed that the toxicity of CAZ was substantially reduced after electrochemical oxidation. The Ti/Ti4O7-rGO/Ce-PbO2 electrode exhibited a constant degradation efficiency (> 99 %) after 10 consecutive cycles, and its service life can reach 3000 min. Furthermore, CAZ maintained a high removal efficiency in swine wastewater. This study provides a new approach toward fabricating a Ce-PbO2 electrode with Ti4O7-rGO middle layer for the degradation of antibiotics in wastewater.

Boosting hydroxyl radical generation for highly efficient electrooxidation of sulfamethazine via facile doping strategy

The one-electron water oxidation reaction (WOR) to generates hydroxyl radicals (•OH) plays a pivotal role in electrochemical advanced oxidation processes (EAOPs). In this study, we present a novel and facile strategy involving Ho-doping to regulate the electronic configuration of the conventionally nonactive PbO2 electrode. Experimental findings demonstrate that PbO2 doped with 2.4% Ho achieves the highest degradation performance of sulfamethazine (SMZ) (∼100%; kobs = 0.093 min−1) and highest •OH generation efficiency with a relatively concentration of •OH = 1.9 × 107. The doped electrodes exhibit a notable enhancement compare to the undoped electrode, which elevating SMZ degradation efficiency and •OH generation by factors of 1.45 and 3.8, respectively. Electrochemical characterization and degradation results elucidate that the modulation of electron transfer rate and oxygen evolution potential are crucial factors governing the performance of the Ho-doped PbO2 anode. Specifically, maintaining a suitably high oxygen evolution potential (OEP) enables the thermodynamically feasible production of •OH, while a relatively fast electron transfer rate ensures the generation of H2O+ (the oxidation precursor of •OH) with kinetic feasibility. Furthermore, a degradation pathway for SMZ is proposed based on the identification of transformation mechanism using density functional calculation (DFT) and the detection of intermediates via LC-MS/MS. This study provides an universal strategy for simultaneously enhancing the OEP and optimizing the electron transfer rate of an EAOP anode through the modulation of anodic electronic configuration, thereby advancing the field of efficient water treatment applications.

Preparation of La-doped Ti/SnO2-Sb2O4 anode and its electrochemical oxidation performance of rhodamine B.

In this paper, La-doped Ti/SnO2-Sb2O4 electrode was prepared by electrodeposition and used for electrochemical degradation of rhodamine B. The optimum preparation conditions of the electrode were optimized as deposition time of 15min and calcination at 500 ℃ for 2h. The water treatment conditions were selected as initial pH 3.0, electrolyte Na2SO4 concentration 0.1M, current density 30mAcm-2, and initial rhodamine B concentration 20mg L-1; the color and TOC removal of RhB reached 99.78% and 82.41% within 30min. The FESEM, XRD, XPS, CV, LSV, and EIS characterization studies demonstrated that Ti/SnO2-Sb2O4-1%La electrode had a dense structure and the highest oxygen evolution potential (2.14V) and lowest charge transfer resistance (0.198 Ω cm-2), indicating that doped La has lower energy consumption. Moreover, La doping can expand the specific surface area, active site, performance of pollutant degradation, and service life of the electrode. Especially, the service life of Ti/SnO2-Sb2O4-1%La is increased by three times, and the maximum life span reaches 90min (1000mAcm-2, 1M H2SO4). Free radical quenching experiments show that ·OH plays a major role in the degradation of RhB. The Ti/SnO2-Sb2O4-1%La electrode prepared in this paper and its results will provide data support and reference for the design of efficient electrocatalytic electrode.

Electro-oxidation of Ibuprofen using carbon-supported SnOx-CeOx flow-anodes: The key role of high-valent metal

Exploiting electrochemically active materials as flow-anodes can effectively alleviate mass transfer restriction in an electro-oxidation system. However, the electrocatalytic activity and persistence of the conventional flow-anode materials are insufficient, resulting in limited improvement in the electro-oxidation rate and efficiency. Herein, we reported a rational strategy to substantially enhance the electrocatalytic performance of flow-anodes in electro-oxidation by introducing the redox cycle of high-valent metal in a suitable carbon substrate. The characterization suggested that the SnOx-CeOx/carbon black (CB) featured well-distributed morphology, rapid charge transfer, high oxygen evolution potential, and strong water adsorption, and stood out among three kinds of SnOx-CeOx loaded carbon materials. Mechanistic analysis indicated that the redox cycle of Ce species played a key role in accelerating the electron transfer from SnOx to CB directionally and could continuously create the electron-deficient state of the SnOx, thereby sustainably triggering the generation of ·OH. All these features enabled the resulting SnOx-CeOx/CB flow-anode to accomplish a calculated maximum kinetic constant of 0.02461 1/min, a higher current efficiency of 47.1%, and a lower energy consumption of 21.3 kWh/kg COD compared with other conventional flow-anodes reported to date. Additionally, SnOx-CeOx/CB exhibited excellent stability with extremely low leaching concentrations of Sn and Ce ions. This study provides a feasible manner for efficient water decontamination using the electro-oxidation system with SnOx-CeOx/CB.

Fabrication of Ti/SnO2-Sb electrodes containing RuO2 interlayer for efficient electrocatalytic oxidation of caprolactam wastewater

The low effectiveness and poor endurance of the electrodes prevent electrocatalytic oxidation from being widely used to treat organic chemicals in wastewater.Here, the coating pyrolysis process was used to successfully create a Ti/SnO2-Sb containing an interlayer of RuO2. The Ti/RuO2/SnO2-Sb surpassed the conventional Ti/SnO2-Sb in both electrocatalytic activity and electroactive surface area. The Ti/RuO2/SnO2-Sb have higher oxygen evolution potential(OEP), better coverage, lower resistance, and less energy consumption with the introduction of RuO2 interlayer. Moreover, the Ti/RuO2/SnO2-Sb exhibited 1.88 times the rate constant of chemical oxygen demand(COD) degradation in caprolactam wastewater furthermore a 25 times rise in service life over conventional Ti/SnO2-Sb.

Mechanism of anodic activation of chloride to generate singlet oxygen for fast organic removal using an innovative anode

Electrochemical persulfate activation (E-PS) has recently emerged as a highly effective advanced oxidation process in water decontamination. However, the presence of chloride ions (Cl−) in waters can accelerate anodic corrosion as well as lead to the formation of toxic chlorinated byproducts (i.e., ClO4−), limiting its practical application. In this study, we introduce a novel Nd/Bi@SnO2 anode to construct E-PS, which exhibits high stability in chloride-containing water with a long-expected service lifetime of 13.7 years. The Nd/Bi@SnO2 electrode can effectively convert Cl− to reactive chlorine with the assistance of PMS, triggering singlet oxygen (1O2) generation for superior organic removal while avoiding toxic chlorinated byproducts (i.e., ClO4−) generation as well as greatly reducing the energy consumption. Comprehensive structural and electrochemical characterization results demonstrate Nd/Bi co-doping introduces oxygen vacancy on Nd/Bi@SnO2, enabling the anode with high oxygen evolution potential, excellent conductivity and superior stability. Scavenging experiments and electron paramagnetic resonance illustrate the generation of various reactive species in the system, among which 1O2 predominantly contributes to organic removal and results in harmless intermediates. This innovative approach transforms Cl− into ROSs for eco-friendly, energy-efficient water decontamination.

Electrochemical treatment of antibiotic wastewater containing ceftriaxone sodium by porous Ti/Magnéli Ti4O7 nanotube arrays

In this study, porous Ti/Magnéli Ti4O7 nanotube arrays (NTA) was fabricated to pretreat antibiotic wastewater. Characterization of the Ti4O7-NTA illustrated that highly ordered NTA was successfully generated on the porous Ti substrate, which enlarged the specific surface area by 1.67 times. The Ti4O7-NTA has a high oxygen evolution potential (2.60 V) as well as low interfacial charge transfer resistance (4.479 Ω cm−2). Ceftriaxone sodium (CRO) was completely removed from raw antibiotic wastewater after 3 h of treatment by the Ti4O7-NTA, under optimal operation conditions. The biodegradability and toxicity of the wastewater were also significantly enhanced and reduced, as the BOD/COD and EC50,48h values were increased to 0.48 and 57.62 % ± 2.16 %, respectively. The possible degradation pathway of CRO was proposed by LC‒MS. Cathodic polarization was proven to be an effective way to ensure the long-term durability of the Ti4O7-NTA.

Electrochemical detoxification of tetrabromobisphenol A-contaminated water using Ti/SnO2-Sb/PbO2-Ce anodic membrane

Degradation of refractory organics has been limited by their low mass-transport rates in conventional flow-by operated electrochemical reactors. This study explores for the first time the development of porous titanium (Ti)-based metal oxide anodic membrane for efficient flow-through degradation of recalcitrant tetrabromobisphenol A (TBBPA). For this purpose, a duplexed Ti/SnO2-Sb/PbO2-Ce anodic membrane was successfully prepared by sol-gel and electrodeposition methods. Ti/SnO2-Sb/PbO2-Ce exhibited improved mechanical and electrochemical stability, larger electrochemical surface area, higher oxygen evolution potential and lower charge transfer resistance, as compared to its mono-layered rival (Ti/SnO2-Sb). The switching from flow-by to flow-through operation resulted in an increased mass transfer rate constant and narrowed diffusion layer thickness of Ti/SnO2-Sb/PbO2-Ce. In the flow-through mode, Ti/SnO2-Sb/PbO2-Ce enabled the complete TBBPA removal at a relatively low electric energy (0.11 kWh m−3). The TBBPA removal was ascribed to the direct anodic oxidation and indirect anodic oxidation incurred by absorbed HO, free HO and 1O2. The intermediate products, which were arisen from the attack of TBBPA by these reactive species, were identified. We further estimated their acute toxicities and bioaccumulation factors. This research proposed a robust electrochemical filtration approach for detoxification of TBBPA-contaminated water.

Degradation of polyvinyl chloride microplastics via electrochemical oxidation with a CeO2–PbO2 anode

As an emerging organic pollutant, microplastics (MPs) pose a serious threat to the water environment and human health. Effective water treatment processes are urgently needed to remove MPs from the aquatic environment. Herein, an electrocatalytic oxidation system with a CeO2-modified PbO2 anode (marked as CeO2–PbO2) was proposed for the degradation of polyvinyl chloride microplastics (PVC-MPs). When the CeO2 concentration in the electrodeposition solution was 0.005 M, the obtained CeO2–PbO2 electrode had the best electrocatalytic activity due to its denser structure, higher oxygen evolution potential, and more active sites. After 6 h of electrolysis, the weight loss of PVC-MPs at the CeO2–PbO2-0.005 anode was 38.67%, greatly higher than 16.67% at the pristine PbO2 anode. To explore the degradation mechanism of PVC-MPs, the surface morphologies, elemental states, and functional groups of PVC-MPs were compared before and after electrochemical treatment, and the formed intermediates were identified. Experimental results revealed that the PVC backbones were broken, the CC double bonds were oxidized or oxidatively cleaved into small molecules, and the dechlorination reaction occurred in the electrochemical oxidation process. As a result, the particle size of the PVC-MPs decreased significantly, lots of cracks appeared and many small pieces were formed on the surface of the PVC-MPs.

Porous carbon/minerals interwoven particle electrodes co-constructed by residual carbon and ash from coal gasification fine slag and its synergistic electrocatalytic mechanism

Complex distribution forms of carbon/ash in coal gasification fine slag (GFS) make it impossible to separate precisely. A combined alkali fusion-polymerization-hydrothermal process was designed to synthesize porous carbon/minerals interwoven particle electrodes (FSAPH) co-constructed by carbon/ash from GFS for electrooxidation treatment of m-cresol wastewater. Based on the hydrogen bonding and coordination capabilities of polyaniline (PAIN), the deconstructed aluminosilicate was regenerated in sheet-like form dispersedly on carbon matrix, effectively enhancing synergistic behavior of carbon and minerals. The electrochemical assessment exhibited superior properties, including a large voltammetry charge of 9.533 mC/cm3, high oxygen evolution potential of 2.15 V, low charge-transfer resistance of 0.36 Ω, and excellent cycle stability. The three-dimensional electrode filled with 0.15 g FSAPH performed pre-adsorption of m-cresol without electricity. Intraparticle diffusion is mainly controlled by SiOSi/AlOH groups on the mineral surface, and the adsorption rate constant KS1 reached 0.491·min−1. After being electrified, AlOH converted H2O2 via three pathways to generate reactive oxygen species (ROS). The rate-determining step in path 2 was the entry of oxygen atoms in OH into the AlOH lattice with the lowest energy barrier of 1.71 kcal/mol. 79.61 mg/L m-cresol can be rapidly degraded within 24 min, 2.6 times that of the two-dimensional electrode system. The electrostatic attraction of carbon ensured the continuous and rapid supply of H2O2 near mineral active sites due to the carbon/minerals interwoven structure. Extensive catalytic sites in thin sheet-like minerals accelerated the electrooxidation of m-cresol on carbon, boosting the catalytic reaction kinetics. Hence, the study realized the comprehensive utilization of carbon/ash in GFS and waste treatment with waste.

Boosting electrochemical oxidation of As(III) on Fe-doped RuO2/PEDOT/SnO2 nanocomposite anode: Fabrication, performance and mechanism

Design of electrode materials for stable and efficient electrocatalytic oxidation of As(Ⅲ) in arsenic-contaminated groundwater poses a great challenge due to the rapid deactivation of catalysts resulting from the high oxygen evolution potential (OEP) and considerable barrier to generating reactive oxygen species (ROS). Herein, an innovative TNAs/SnO2/PEDOT/Fe(III)-RuO2 multilayer electrode was synthesized by utilizing a PEDOT-coated SnO2 interlayer as a supportive framework to combine Fe-doped amorphous RuO2 catalytic layer with TiO2 nanotube array substrate. Such electrode exhibited high activity and stability for the oxidation of As(III) to As(V) due to the large surface area provided by the TiO2 nanotube arrays and the SnO2/PEDOT interlayer for facilitating the growth of the catalytic layer. The electrochemically active surface area of the electrode reached as high as 31.7 mF/cm2. Impressively, the doping of Fe into RuO2 layer led to a remarkable increase in the OEP value to 3.12 V, which boosted the indirect oxidation process mediated by ROS at a lower potential to achieve the As(III) oxidation ratio of 98.5%. DFT calculations revealed that the Fe-doped amorphous RuO2 weakened the adsorption strength of ·OH and ·SO4− intermediates and lowered the energy barrier for generating ROS. Combined with ESR results, the formation of ·OH and ·SO4− with strong oxidizing properties was fully verified, providing further evidence for the involvement of ROS as the main mediator of the oxidation mechanism of As(III). This work may provide valuable perspectives into the design of catalytic layer structures and heteroatom doping modifications for composite-coated electrodes.

Development of SDS-Modified PbO2 Anode Material Based on Ti3+ Self-Doping Black TiO2NTs Substrate as a Conductive Interlayer for Enhanced Electrocatalytic Oxidation of Methylene Blue.

Efficient and stable electrode materials are urgently required for wastewater treatment in the electrocatalytic degradation of toxic and refractory organic pollutants. Ti3+ self-doping black TiO2 nanotube arrays (Ti/B-TiO2-NTs) as an interlayer were used for preparing a novel PbO2 electrode via an electrochemical reduction technology, and a sodium dodecyl sulfate (SDS)-modified PbO2 catalytic layer was successfully achieved via an electrochemical deposition technology. The physicochemical characterization tests showed that the Ti/B-TiO2-NTs/PbO2-SDS electrodes have a denser surface and finer grain size with the introduction of Ti3+ in the interlayer of Ti/TiO2-NTs and the addition of SDS in the active layer of PbO2. The electrochemical characterization results showed that the Ti3+ self-doping black Ti/TiO2-NTs/PbO2-SDS electrode had higher oxygen evolution potential (2.11 V vs. SCE), higher electrode stability, smaller charge-transfer resistance (6.74 Ω cm-2), and higher hydroxyl radical production activity, leading to it possessing better electrocatalytic properties. The above results indicated that the physicochemical and electrochemical characterization of the PbO2 electrode were all enhanced significantly with the introduction of Ti3+ and SDS. Furthermore, the Ti/B-TiO2-NTs/PbO2-SDS electrodes displayed the best performance on the degradation of methylene blue (MB) in simulated wastewater via bulk electrolysis. The removal efficiency of MB and the chemical oxygen demand (COD) could reach about 99.7% and 80.6% under the optimal conditions after 120 min, respectively. The pseudo-first-order kinetic constant of the Ti/B-TiO2-NTs/PbO2-SDS electrode was 0.03956 min-1, which was approximately 3.18 times faster than that of the Ti/TiO2-NTs/PbO2 electrode (0.01254 min-1). In addition, the Ti/B-TiO2-NTs/PbO2-SDS electrodes showed excellent stability and reusability. The degradation mechanism of MB was explored via the experimental identification of intermediates. In summary, the Ti3+ self-doping black Ti/TiO2-NTs/PbO2-SDS electrode is a promising electrode in treating wastewater.