Electrochemical Oxidation Research Articles

Medium-entropy perovskite Pr0.4Ba0.2Ca0.2La0.2Co0.2Fe0.8O3 as a promising bifunctional electrocatalyst for electrochemical energy conversion device

Reversible solid oxide cells (R-SOCs) are considered to be a promising energy conversion device that can achieve efficient conversion between fuel and electrical energy. However, there are still significant challenges in developing a promising bifunctional electrocatalyst as an electrode material for R-SOC devices. Here, a medium-entropy perovskite Pr0.4Ba0.2Ca0.2La0.2Co0.2Fe0.8O3 (PBCLCF) is designed to enhance the electrochemical oxidation and reduction activity. Under hydrogen atmosphere, cobalt metals are in situ exsolved from the perovskite structure, accompanied by partial phase transformation (denoted as R-PBCLCF). Characterizations show that PBCLCF and R-PBCLCF can increase the concentration of oxygen vacancies, thereby enhancing oxygen migration ability. Combined with electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis, the medium-entropy PBCLCF exhibits better oxygen reduction reaction (ORR) activity and R-PBCLCF shows better hydrogen oxidation reaction (HOR) activity. Furthermore, the oxygen dissociation is identified as the rate-determining step (RDS) in the ORR process, whereas the HOR process is dominated by the hydrogen adsorption and dissociation. The single cell with (R-)PBCLCF showcases remarkable reversible performance. When O2 is employed as the oxidant and H2 as the fuel, this cell achieves a maximum power density of 468.1 mW cm−2 in solid oxide fuel cell (SOFC) mode at 700 °C. Moreover, when O2 is employed as the oxidant and humidified H2 (30 %H2O) as the fuel, the current density of the cell in solid oxide electrolysis cell (SOEC) mode is −647.3 mA cm−2 at 1.3 V and 700 °C.

Surface Extraction Process During Initial Oxidation of Pt(111): Effect of Hydrophilic/Hydrophobic Cations in Alkaline Media.

The surface oxidation states of the metal electrodes affect the activity, selectivity, and stability of the electrocatalysts. Oxide formation and reduction on such electrodes must be comprehensively understood to achieve next-generation electrocatalysts with outstanding performance and stability. Herein, the initial electrochemical oxidation of Pt(111) in alkaline media containing hydrophilic and hydrophobic cations is investigated by X-ray crystal truncation rod (CTR) scattering, infrared (IR) spectroscopy, and nanoparticle-based surface-enhanced Raman spectroscopy (SERS). Structural determination using X-ray CTR revealed surface buckling and Pt extraction at the initial stage of surface oxidation, depending on the cationic species. Vibrational spectroscopy is performed to identify the potential- and cation-dependent formation of three oxide species (IR-active OHad, Raman-active OHad/Oad(H2O), and Raman-active Oad). Hydrophilic alkali metal cations (Li+) inhibit surface roughening via irreversible oxide formation. Hydrophilic Li+ can strongly stabilize IR-active OHad, hindering the extraction of Pt surface atoms. Interestingly, bulky hydrophobic cations such as tetramethylammonium (TMA+) cation also reduce the extent of irreversible oxidation despite the absence of IR-active OHad. Hydrophobic TMA+ inhibits the formation of Raman-active OHad/Oad(H2O) associated with Pt extraction. In contrast, the moderate hydrophilicity of K+ has no protective effect against irreversible oxidation. Moderate hydrophilicity enables the coadsorption of Raman-active OHad/Oad(H2O) and Raman-active Oad. The electrostatic repulsion between Raman-active OHad/Oad(H2O) and neighboring Raman-active Oad promotes Pt extraction. These results provide insights into controlling the surface structures of electrocatalysts using cationic species during the oxide formation and reduction processes.

Unveiling the decomposing and mineralizing mechanism of novel perfluoroalkyl acids via hydroxyl radical dominated electrochemical oxidation

A cerium-doped Sb2S3 anode is successfully fabricated for perfluoroalkyl acids (PFAAs) degradation via a hydroxyl radical dominant electrochemical oxidation (EO) coupled peroxymonosulfate (PMS) reaction. Various PFAAs can be efficiently removed within 25 min with high mineralization and low energy consumption. The hydroxyl radical, sulfate radical, and electron transfer are responsible for PFAAs degradation, and the hydroxyl radical played a dominant role. The electron can be moved from the highest occupied molecular orbital of these PFAAs to the lowest unoccupied molecular orbital of PMS via potential energy difference, further decomposing PMS to generate hydroxyl and sulfate radical for PFAAs degradation. Besides, the corresponding degradation pathway, defluorination, and Gibbs free energy of the reaction for each PFAAs were elucidated based on the identified intermediates and density functional theory calculations. The current study provides insight into the efficient decomposition mechanism of various PFAAs during EO and highlights its promising potential in environmental remediation.

Anodic oxidation of esomeprazole in water by carbon coated titanium (C/Ti) electrode: Optimization and degradation analysis

AbstractEsomeprazole (ESO) is one of the proton pump inhibitors (PPIs) that is commonly used to treat extreme acidity and gastrointestinal irritation. Since it is used at a high rate, it is now classified as a pollutant of emerging concern (CEC). ESO gravely jeopardizes the health of living beings because it persists in water and wastewater sources even after standard treatment. Studies on the effective removal of PPIs, especially ESO, are scarce. In the current study, esomeprazole is disintegrated in water using electrochemical oxidation (EO). Titanium cathode with sodium sulfate electrolyte and carbon coated titanium (C/Ti) anode were used to apply EO. Through optimization studies utilizing COD measurement, it was discovered that 93% of the COD could be removed at pH 3, 60 mM sodium sulfate concentration, 300 min treatment period, and 115 mA cm−2 current density. Whereas TOC research revealed only 44% mineralization, HPLC‐PDA experiments revealed 100% ESO transformation. High resolution mass spectrometry (HRMS) studies were used to propose a degradation mechanism and pathway. The primary processes of degradation included desulfurization, thioperoxole group formation, sulfinyl benzimidazole group breakage, and demethylation. More than 20 reuses of the anode and cathode materials were possible without significantly lowering their oxidation efficiency.

Laser-Induced Preparation of Anderson-Type Polyoxometalate-Derived Sulfide/Oxide Electrocatalysts for Electrochemical Water Oxidation.

Developing cost-effective and high-active electrocatalysts is vital to enhance the electrocatalytic performance for oxygen evolution reaction (OER). However, traditional pyrolysis methods require complicated procedures, exact temperatures, and long reaction times, leading to high costs and low yields of electrocatalysts in potential industrial applications. Herein, a rapid and economic laser-induced preparation strategy is proposed to synthesize three bimetallic sulfide/oxide composites (MMoOS, M=Fe, Co, and Ni) on a nickel foam (NF) substrate. A focused CO2 laser with high energy is applied to decompose Anderson-type polyoxometalate (POM)-based precursors, enabling the creation of abundant heteropore and defective structures in the MMoOS composites that have multi-components of MS/Mo4O11/MoS2. Remarkably, owing to the structural interactions between the active species, FeMoOS shows superior electrocatalytic performance for OER in an alkaline medium, exhibiting a low overpotential of 240 mV at 50 mA cm-2, a small Tafel slope of 79 mV dec-1, and good durability for 80 h. Physical characterizations after OER imply that partially dissolved Mo-based species and new-formed NiO/NiOOH can effectively uncover abundant active sites, fasten charge transfer, and modify defective structures. This work provides a rapid laser-induced irradiation method for the synthesis of POM-derived nanocomposites as promoted electrocatalysts.

Molybdenum, tungsten doped cobalt phosphides as efficient catalysts for coproduction of hydrogen and formate by glycerol electrolysis

H2 and formate are important energy carriers in fuel-cells and feedstocks in chemical industry. The hydrogen evolution reaction (HER) coupling with electro-oxidative cleavage of thermodynamically favorable polyols is a promising way to coproduce H2 and formate via electrochemical means, highly active catalysts for HER and electrooxidative cleavage of polycols are the key to achieve such a goal. Herein, molybdenum (Mo), tungsten (W) doped cobalt phosphides (Co2P) deposited onto nickel foam (NF) substrate, denoted as Mo-Co2P/NF and W-Co2P/NF, respectively, were investigated as catalytic electrodes for HER and electrochemical glycerol oxidation reaction (GOR) to yield H2 and formate. The W-Co2P/NF electrode exhibited low overpotential (η) of 113 mV to attain a current density (J) of -100 mA cm-2 for HER, while the Mo-Co2P/NF electrode demonstrated high GOR efficiency for selective production of formate. In situ Raman and infrared spectroscopic characterizations revealed that the evolved CoO2 from Co2P is the genuine catalytic sites for GOR. The asymmetric electrolyzer based on W-Co2P/NF cathode and Mo-Co2P/NF anode delivered a J=100 mA cm-2 at 1.8 V voltage for glycerol electrolysis, which led to 18.2% reduced electricity consumption relative to water electrolysis. This work highlights the potential of heteroelement doped phosphide in catalytic performances for HER and GOR, and opens up new avenue to coproduce more widespread commodity chemicals via gentle and sustainable electrocatalytic means.

A hybrid electrochemical system for spontaneous green‑hydrogen production with simultaneous desalination using catechol oxidation

Green hydrogen, commonly produced through water electrolysis, has attracted considerable attention owing to its energy-efficient and eco-friendly properties. However, since conventional water electrolysis system has fatal drawbacks owing to the high process cost and energy requirements, various approaches are being adopted to increase its energy efficiency. In this study, a novel hybrid system for green hydrogen production was designed by replacing the oxygen evolution reaction (OER) with electrochemical oxidation of catechol (CAT). CAT is an environmental pollutant generated by diverse industries and needs to be further treated because of its toxicity to humans and nature. Accordingly, to facilitate the degradation of CAT and increase the energy efficiency, the pH values of the anolyte (containing CAT) and catholyte were adjusted to alkali and acid, respectively. Two types of ion-exchange membranes (IEMs; anion-/cation-exchange membranes) were coupled to divide the hybrid cell into three compartments, and a buffer solution (NaCl solution) was injected between the IEMs. As a result, the hybrid system output 3.75 mW/cm2 of electricity, spontaneously produced hydrogen with 4.2 mL/h of hydrogen production rate and removed ions from the buffer solution with 0.46 mg/cm2∙min of high desalination rate.

Electrochemical decolorization of liquid digestate from coffee waste biomass using a boron-doped diamond anode

AbstractLiquid digestate can be used to provide nutrients for microalgae cultivation but the medium needs to be clear and colorless. The aim of this work was to use liquid digestate from coffee waste biomass to produce a light-permeable medium for microalgae cultivation. A boron-doped diamond anode was applied for electrochemical decolorization of the digestate. The electrochemical oxidation process reduced the platinum-cobalt color value by up to 97% and the chemical oxygen demand by 84.1%. After electrochemical oxidation, 87.4% of the ammonium nitrogen (NH4-N) was retained. Decolorization of the spent coffee grounds liquid digestate was compared with that of dairy cow manure liquid digestate. It took 90 min longer to fully decolorize the spent coffee grounds liquid digestate compared with the dairy cow manure liquid digestate. The boron-doped diamond anode performed better in the decolorization than Ti/IrO2 and Ti/Pt anodes. The effects of the initial Fe2+ concentration and current on the electrochemical oxidation process were also evaluated. Increasing the initial Fe2+ concentration enhanced the Fenton reaction and chemical oxygen demand removal. A higher current enhanced the electrochemical decolorization process and side reactions. Electrochemical oxidation using a boron-doped diamond anode is a promising method for producing an appropriate medium for microalgae cultivation because it promotes decolorization of liquid digestate and retains most of the NH4-N.

Removal of N-nitrosopyrrolidine from GAC by a three-dimensional electrochemical reactor: degradation mechanism and degradation path.

Nitrogen-containing disinfection by-products (N-DBPs) produced in the process of drinking water disinfection are widely concerning due to the high cytotoxicity and genotoxicity. It is due to the difficulty of natural degradation of N-DBPs in water and the fact that conventional treatment systems do not effectively treat N-DBPs in drinking water. In this study, N-nitrosopyrrolidine (NPYR) in water was electrocatalytically degraded by a three-dimensional electrode reactor (3DER). This system applied graphite plates as anode and cathode. The granular activated carbon (GAC) was used as third electrode. The degradation of NPYR using a continuous flow three-dimensional electrode reactor was investigated by examining the effects of flow rate, current density, electrolyte concentration, and pollutant concentration on the degradation efficiency, energy consumption, and reaction kinetics of GAC particle electrodes. The results showed that the optimal operating conditions were flow rate = 0.45mL/min, current density = 6mA/cm2, Na2SO4 concentration = 0.28mol/L, and NPYR concentration = 20mg/L. Under optimal conditions, the degradation of NPYR exceeded 58.84%. The main contributor of indirect oxidation was deduced from free radical quenching experiments. NPYR concentration was measured by GC-MS with DB-5 capillary column, operating in full scan monitoring mode for appropriate quantification of NPYR and intermediates. Based on the identification of reaction intermediates, a possible pathway for the electrochemical oxidation of NPYR on GAC particle electrodes was proposed.

Enhancing Oxygen Evolution Reaction through In Situ Electrochemical Oxidation for the Structural Control of Co-Fe Prussian Blue Analogue

The development of exceptionally efficient catalysts for the oxygen evolution reaction (OER) and gaining a deep understanding of their activity is essential for advancing electrochemical conversion technologies. Prussian blue analogues (PBAs) serve as promising pre-catalysts for the OER. However, PBAs, typically prepared through the conventional co-precipitation method, exhibit a lower active site density and limited electrical transport, making them suitable precursors for the derivation of PBA derivatives. In this research, we identified a significant enhancement in the electrocatalytic performance of Co-Fe Prussian blue analogue (CoFe PBA) through electrochemical oxidation. The cubic CoFe PBA was synthesized by one-step co-precipitation method using adjusting the amount of sodium citrate and potassium ferricyanide. After the electrochemical treatment, CoFe PBA demonstrates remarkable attributes, including a low overpotential of 331mV at a current density of 10mA·cm-2, a small Tafel slope of 50.4mV·dec-1, and excellent long-term stability during electrolysis in a 1M KOH alkaline medium for over 37h. Moreover, the electrochemical oxidation of CoFe PBA was comprehensive, employing techniques such as Transmission electron microscope, Powder X-ray diffraction, and X-ray photoelectron spectroscopy. These analyses confirmed the presence of real active substances, including CoOOH and a part of FeOOH species, further supporting the observed improvements in electrocatalytic activity.

Recovery of metal ions in lithium iron phosphate powder and lithium nickel-cobalt-manganate powder by electrochemical oxidation

In recent years, lithium-ion batteries have been increasingly used in electric and hybrid vehicles. It is anticipated that the first lithium-ion batteries will be discarded at the height of their useful lives in 2025, so developing an effective and ecologically friendly recycling process is essential. In this study, an electrochemical cathode synergism is proposed for the electro-catalyzed oxidation of lithium nickel cobalt manganese oxide powder and lithium iron phosphate powder to extract metal. The oxidation of Fe2+ and the release of Li+ (98 %) in LiFePO4 and the leaching of Ni (92 %), Co (91 %), Mn (94 %) and Li (97 %) from its NCM523 were mainly triggered by the rapid attack of a large amount of OH during advanced oxidation. The leaching kinetic analysis showed that the leaching system for electrochemical leaching of binary and ternary cathode materials was a chemical reaction control model, and the leaching thermodynamic analysis showed that the dissolution of each metal ion was feasible in this leaching environment. The suggested recycling technique utilizes fewer chemicals and generates less waste when compared to previous recycling techniques. The method offers a fresh approach to environmentally friendly recycling for spent lithium-ion battery leaching and recycling.

Continuous Production of Ethylene and Hydrogen Peroxide from Paired Electrochemical Carbon Dioxide Reduction and Water Oxidation

AbstractPaired electrolysis offers an auspicious strategy for the generation of high‐value chemicals, at both the anode and cathode, in an integrated electrochemical reactor. Through efficient electron utilization, routine product misuse at overlooked electrodes can be prevented. Here, an original paired electrosynthetic system is reported that can convert CO2 to ethylene (C2H4) at the cathode, and water to hydrogen peroxide (H2O2) at the anode under a single pass of electric charge. Amongst various investigated copper (Cu) nanomorphologies, the bespoke mixed Cu nanowire/nanoparticle catalyst recorded a peak C2H4 Faraday efficiency (FE) of 60% following 370 h of electrolysis at 200 mA cm−2, while the tailored boron‐doped diamond (BDD) anode accumulated an unprecedented ≈1% w/w of H2O2 in 4 m K2CO3 upon applying 300 mA cm−2 for 10 h. When paired, the dual C2H4‐H2O2 electrochemical cell attains a combined FE of 120% for 50 h at 200 mA cm−2, a combined energy efficiency (EE) of 69%, and a 50% decrease in the overall electrical energy consumption (EEC) compared to the individual electrosynthesis of C2H4 and H2O2.

Preparation of electrochemical sensor for detection of cancer medicine doxorubicin based on multi-walled carbon nanotube composites modified electrode

In order to create an electrochemical sensor for doxorubicin (DXB), an effective cancer treatment, multi-walled carbon nanotubes—a modified glassy carbon electrode made of mesoporous silica nanocomposite—were created in this work. Examining the mSiO2@MWCNTs nanocomposite's structure and composition using FTIR, XPS, and SEM revealed the combination of mSiO2 and MWCNTs nanostructure on the modified electrode surface. Studies on the electrochemical determination of DXB utilizing cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methodologies showed that mSiO2@MWCNTs/GCE exhibited excellent sensitivity, selectivity, and precision. MWCNTs and mesoporous silica in the improved electrode work together to improve the sensor's overall performance by enhancing stability and sensitivity in the electrochemical oxidation of DXB. The sensor's linear range was found to be 30–750 μM, with a sensitivity of 0.05123 μA/μM and a detection limit of 14 nM, according to the results. The mSiO2@MWCNTs/GCE shows properties suitable for real sample analysis. The creation of this sensor represents a significant advancement in the field of electrochemical sensors and may open the door to the development of more precise and focused drug detection techniques.

Total Synthesis of Dragocins A−C through Electrochemical Cyclization

AbstractThe first total synthesis of dragocins A−C, remarkable natural products containing an unusual C4’ oxidized ribose architecture bridged by a polyhydroxylated pyrrolidine, is presented through a route featuring a number of uncommon maneuvers. Several generations towards the target molecules are presented, including the spectacular failure of a key C−H oxidation on a late‐stage intermediate. The final route features rapid, stereocontrolled access to a densely functionalized pyrrolidine and an unprecedented diastereoselective oxidative electrochemical cyclization to forge the hallmark 9‐membered ring. Preliminary studies suggest this electrochemical oxidation protocol is generally useful.

Application of photoelectrochemical oxidation of wastewater used in the cooling tower water and its influence on microbial corrosion.

Cooling towers are specialized heat exchanger devices in which air and water interact closely to cool the water's temperature. However, the cooling water contains organic nutrients that can cause microbial corrosion (MC) on the metal surfaces of the tower. This research explores the combined wastewater treatment approach using electrochemical-oxidation (EO), photo-oxidation (PO), and photoelectrochemical oxidation (PEO) to contain pollutants and prevent MC. The study employed electro-oxidation, a process involving direct current (DC) power supply, to degrade wastewater. MC studies were conducted using weight loss assessments, scanning electron microscopy (SEM), and x-ray diffraction (XRD). After wastewater is subjected to electro-oxidation for 4 h, a notable decrease in pollutants was observed, with degradation efficiencies of 71, 75, and 96%, respectively. In the wastewater treated by PEO, microbial growth is restricted as the chemical oxygen demand decreases. A metagenomics study revealed that bacteria present in the cooling tower water consists of 12% of Nitrospira genus and 22% of Fusobacterium genus. Conclusively, PEO serves as an effective method for treating wastewater, inhibiting microbial growth, degrading pollutants, and protecting metal from biocorrosion.

Fine‐tuning electronic structure of N‐doped graphitic carbon‐supported Co‐ and Fe‐incorporated Mo2C to achieve ultrahigh electrochemical water oxidation activity

AbstractMo2C is an excellent electrocatalyst for hydrogen evolution reaction (HER). However, Mo2C is a poor electrocatalyst for oxygen evolution reaction (OER). Herein, two different elements, namely Co and Fe, are incorporated in Mo2C that, therefore, has a finely tuned electronic structure, which is not achievable by incorporation of any one of the metals. Consequently, the resulting electrocatalyst Co0.8Fe0.2–Mo2C‐80 displayed excellent OER catalytic performance, which is evidenced by a low overpotential of 214.0 (and 246.5) mV to attain a current density of 10 (and 50) mA cm−2, an ultralow Tafel slope of 38.4 mV dec−1, and long‐term stability in alkaline medium. Theoretical data demonstrates that Co0.8Fe0.2–Mo2C‐80 requires the lowest overpotential (1.00 V) for OER and Co centers to be the active sites. The ultrahigh catalytic performance of the electrocatalyst is attributed to the excellent intrinsic catalytic activity due to high Brunauer–Emmett–Teller specific surface area, large electrochemically active surface area, small Tafel slope, and low charge‐transfer resistance.

Electrocatalytic hydrogen peroxide generation using WO3 nanoparticle-decorated sodium niobate microcubes

The current work studies the electrocatalytic performance of NaNbO3 microcubes decorated with WO3 nanoparticles on Printex L6 at varying concentrations (1%, 3%, 5%, and 10% by weight) for H2O2 electrogeneration aiming for future use in electrochemical advanced oxidation processes for organic pollutant degradation·H2O2 electrogeneration was studied using oxygen reduction reaction (ORR) with the rotating ring-disk electrode (RRDE) technique. Electrochemical results revealed an improvement in H2O2 electrogeneration for the NaNbO3@WO3/C materials compared to that achieved with Printex L6 carbon. Notably, the 5% NaNbO3@WO3/C electrocatalyst exhibited a higher ring current for oxygen reduction reaction and promoted a 2.1-electron transfer, facilitating a higher rate of H2O2 electrogeneration through the 2-electron mechanism. Also, enhancing oxygen-containing functional groups has shown the capability to thoroughly adjust characteristics and enhance active sites, increasing H2O2 electrogeneration. These findings suggest that 5% NaNbO3@WO3/C electrocatalysts hold promise for in situ hydrogen peroxide electrogeneration.

Nickel-Iron-Modified 2D Metal-Organic Framework as a Tunable Precatalyst for Electrochemical Water Oxidation.

Mixed-metal metal-organic framework (MOF)-based water oxidation precatalysts have aroused a great deal of attention due to their remarkable catalytic performance. Yet, despite significant advancement in this field, there is still a need to design new MOF platforms that allow simple and systematic control over the final catalyst's metal composition. Here, we show that a Zr-BTB 2D-MOF could be used to construct a series of Ni-Fe-based oxide hydroxide water oxidation precatalysts with diverse Ni-Fe compositions. In situ Raman spectroscopy characterization revealed that the MOF precatalysts could be electrochemically converted to the active catalysts (NiFeOOH). In turn, it was found that the highest water oxidation activity was obtained with a catalyst containing a 47:53 Ni:Fe molar ratio. Additionally, the obtained catalyst is also active toward electrochemical methanol oxidation, exhibiting high selectivity toward the formation of formic acid. Hence, these results could pave the way for the development of efficient electrocatalytic materials for a variety of oxidative reactions.

Role of Side-Chain Free Volume on the Electrochemical Behavior of Poly(propylenedioxythiophenes).

Mixed ionic/electronic conducting polymers are versatile systems for, e.g., energy storage, heat management (exploiting electrochromism), and biosensing, all of which require electrochemical doping, i.e., the electrochemical oxidation or reduction of their macromolecular backbones. Electrochemical doping is achieved via electro-injection of charges (i.e., electronic carriers), stabilized via migration of counterions from a supporting electrolyte. Since the choice of the polymer side-chain functionalization influences electrolyte and/or ion sorption and desorption, it in turn affects redox properties, and, thus, electrochemically induced mixed conduction. However, our understanding of how side-chain versus backbone design can increase ion flow while retaining high electronic transport remains limited. Hence, heuristic design approaches have typically been followed. Herein, we consider the redox and swelling behavior of three poly(propylenedioxythiophene) derivatives, P(ProDOT)s, substituted with different side-chain motifs, and demonstrate that passive swelling is controlled by the surface polarity of P(ProDOT) films. In contrast, active swelling under operando conditions (i.e., under an applied bias) is dictated by the local side-chain free volume on the length scale of a monomer unit. Such insights deliver important design criteria toward durable soft electrochemical systems for diverse energy and biosensing platforms and new understanding into electrochemical conditioning ("break-in") in many conducting polymers.

In-situ active sites analysis of bifunctional metal-organic frameworks for coupled adsorption and electrochemical oxidation of PPCPs

Pharmaceuticals and personal care products (PPCPs) pose a significant wastewater pollution concern. While electrochemical oxidation is promising, it struggles with slow mass transfer. To address this, we propose a novel strategy utilizing bifunctional metal–organic frameworks (MOFs) that couple an adsorbent with an electrocatalyst. The real active sites within iron-based MOFs responsible for the adsorption of PPCPs are MIL-101(Fe) molecules, while the in-situ formed active sites, α-FeOOH, accelerate the charge transfer under bias, contributing to the electrooxidation of PPCPs. The rapid destruction of adsorbed organics on the dual-functional electrode surface enables to release adsorption sites. This, in turn, paves the way for fast and efficient re-adsorption of PPCPs molecules, consequently promoting mass transfer. Iron-based MOFs exhibit excellent adsorption capacity (∼60 mg g−1 for sulfosalicylic acid, ∼15 mg g−1 for acetaminophen) and electrooxidation ability (94 % removal in 2 h, 31.2 kWh kg−1 COD) with good stability in realistic pharmaceutical wastewater treatment. This study offers a novel strategy for removing PPCPs using molecular electrocatalysts and provides new insights for designing and constructing MOFs for refractory wastewater treatment.