Electron Transfer Capability Research Articles

Fabrication of Ultra-Durable and Flexible NiPx -Based Electrode toward High-Efficient Alkaline Seawater Splitting at Industrial Grade Current Density.

Designing nonprecious metal-based electrocatalysts to yield sustainable hydrogen energy by large-scale seawater electrolysis is challenging to global emissions of carbon neutrality and carbon peaking. Herein, a series of highly efficient, economical, and robust Ni-P-based nanoballs grown on the flexible and anti-corrosive hydrophobic asbestos (NiPx @HA) is synthesized by electroless plating at 25°C toward alkaline simulated seawater splitting. On the basis of the strong chemical attachment between 2D layered substrate and nickel-rich components, robust hexagonal Ni5 P4 crystalline modification, and fast electron transfer capability, the overpotentials during hydrogen/oxygen evolution reaction (HER/OER) are 208 and 392mV at 200mA cm-2 , and the chronopotentiometric measurement at 500mA cm-2 lasts for over 40 days. Additionally, the versatile strategy is broadly profitable for industrial applications and enables multi-elemental doping (iron/cobalt/molybdenum/boron/tungsten), flexible substrate employment (nickel foam/filter paper/hydrophilic cloth), and scalable synthesis (22 cm × 22cm). Density functional theory (DFT) also reveals that the optimized performance is due to the fundamental effect of incorporating O-source into Ni5 P4 . Therefore, this work exhibits a complementary strategy in the construction of NiPx -based electrodes and offers bright opportunities to produce scalable hydrogen effectively and stably in alkaline corrosive electrolytes.

Degradation of bisphenol A in an oxidation system constructed from Mo2C MXene and peroxymonosulfate

The etched Mo2C MXene with a layered structure was characterized as an environmentally friendly catalyst in the bisphenol A (BPA) removal by advanced oxidation. 99.75% of BPA was degraded in the oxidation system constructed using Mo2C MXene and peroxymonosulfate (PMS). The Mo2C MXene was recyclable, with a high removal percentage (89.29%) of BPA after even four cycles. The catalysis of Mo2C MXene on PMS was due to the Mo-deficit vacancy defects. The electron paramagnetic resonance technique and density functional theory (DFT)-based density of states calculations verified defect signals. In addition, the defective Mo2C MXene and PMS have strong binding and electron transfer capabilities. The reactive oxygen species (ROS, including O2•−, 1O2, SO4•−, and •OH) produced by Mo2C MXene activates PMS, leading to BPA degradation. The condensed Fukui function predicted the active sites of the BPA molecule and found that the O1, O2, C3, C4, C6, C12, C15, and C16 sites have higher electrophilic reactivity. The C, C–C bonds, or C4/C16 sites in the isopropyl group connecting the two phenolic rings were attacked first, then further transformed BPA into non-toxic or low toxic small molecule degradation products through a series of reactions such as bond-breaking, addition, hydroxylation, and ring-opening. Moreover, the Mo2C MXene/PMS system has strong applicability in actual water bodies. The study provides valuable insights into PMS activation by two-dimensional MXenes to remove toxic organic pollutants in an aqueous matrix.

Electrochemical performance of Paenibacillus profundus YoMME encapsulated in alginate polymer

Gram-positive bacterium Paenibacillus profundus YoMME, entrapped in an alginate polymer onto graphite paper, preserves its extracellular electron transfer capabilities. A current density of up to 30 mA m−2 was generated at an applied potential of −200 mV (vs. SHE). Fivefold higher initial current density values were recorded at applied potentials of +220 mV and +600 mV. The electrochemical behavior of the encapsulated bioelectrodes has been also explored by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy and evaluated by the parameters of the best-fitted equivalent electric circuit model. Over time the bacteria grow and divide within the alginate matrix, which affects considerably the capacitance and the charge transfer resistance of the coating. The impedance spectra follow the dynamics of the bacterial culture development within the alginate polymer and are useful for the prediction of the bioelectrode performance. A current density of 150 mA m−2 was achieved when the alginate was functionalized by a mixture of the redox dyes thiazolyl blue (MTT) formazan and phenazine methosulfate (PMS). It is supposed that the added artificial mediators facilitate the electron transfer from the bacteria to the electrode surface by forming conductive cascade conduits through the alginate matrix.

One-Step Synthesized Iron-Carbon Core-Shell Nanoparticles to Activate Persulfate for Effective Degradation of Tetrabromobisphenol A: Performance and Activation Mechanism.

Tetrabromobisphenol A (TBBPA), as an emerging endocrine disrupter, has been considered one of the persistent organic contaminants in water. It is urgently necessary to develop an efficient technique for the effective removal of TBBPA from water. Herein, a one-step hydrothermal synthesis route was employed to prepare a novel iron-carbon core-shell nanoparticle (Fe@MC) for effectively activating persulfate (PS) to degrade TBBPA. Morphological and structural characterization indicated that the prepared Fe@MC had a typical core-shell structure composed of a 5 nm thick graphene-like carbon shell and a multi-valence iron core. It can be seen that 94.9% of TBBPA (10 mg/L) could be degraded within 30 min at pH = 7. This excellent catalytic activity was attributed to the synergistic effect of the porous carbon shell and a multi-valence iron core. The porous carbon shell could effectively prevent the leaching of metal ions and facilitate PS activation due to its electron transfer capability. Furthermore, numerous micro-reaction zones could be formed on the surface of Fe@MC during the rapid TBBPA removal process. Radical quenching experiments and electron paramagnetic resonance (EPR) technology indicated that reactive oxygen species (ROS), including OH, SO4-, O2-, and 1O2, were involved in the TBBPA degradation process. Based on density functional theory (DFT) calculation, the carbon atoms linked by phenolic hydroxyl groups would be more vulnerable to attack by electron-rich groups; the central carbon was cracked and hydroxylated to generate short-chain aliphatic acids. The toxicity evaluation provides clear evidence for the promising application potential of our prepared material for the efficient removal of TBBPA from water.

Photocatalytic degradation of reactive brilliant blue KN-R by Ti-doped Bi2O3.

In this study, different compositions of Ti-doped Bi2O3 photocatalytic materials were prepared by chemical solution decomposition method. It was used to degrade reactive brilliant blue KN-R, and then characterized by XRD, SEM, UV-vis DRS, XPS, photocurrent, and other detection methods. The results show that when the catalyst dosage is 1.0g/L and the initial concentration of reactive brilliant blue KN-R is 20mg/L, the degradation rate of pure Bi2O3 to reactive brilliant blue KN-R is 75.30%; the Ti doping amount is 4% (4Ti/Bi2O3), 4Ti/Bi2O3 had the best degradation effect on reactive brilliant blue KN-R, and the degradation rate could reach 93.27%. When 4Ti/Bi2O3 was reused for 4 times, the degradation rate of reactive brilliant blue KN-R only decreased by 6.91%. Doping Ti can inhibit the growth of Bi2O3 grains, making the XRD peak of Ti/Bi2O3 material wider. The pure Bi2O3 particles are larger and the surface is smooth. With the increase of Ti doping content, the surface of Ti/Bi2O3 material grows from roughness to nanofibrous Bi4Ti3O12. The visible light absorption performance and electron separation and transfer ability of Bi2O3 are significantly improved by doping Ti ions. The band gap is reduced from 2.81 to 2.75eV. In conclusion, doping Ti enhances the visible light absorption and electron separation and transfer capabilities of Bi2O3, reduces the band gap, and improves the surface morphology, which makes Bi2O3 have higher photocatalytic performance.

MOFs-derived Mn/C composites activating peroxymonosulfate for efficient degradation of sulfamethazine: Kinetics, pathways, and mechanism

Both manganese oxides (MnOx) and carbon materials hold promise for persulfate activation to remediate polluted waterbodies. However, the aggregation of MnOx during the calcination synthesis and lower activity to persulfate of carbon materials seriously limit their industrial application. In this work, two Mn/C composites (MnOx-NA and MnOx-A) were synthesized from manganese-metal organic frameworks (MOFs) under nitrogen atmosphere and air atmosphere calcination respectively. The prepared MnOx-NA exhibited more excellent peroxymonosulfate (PMS) activation performance than MnOx-A, and almost 100% sulfamethazine (SMT) could be removed by the MnOx-NA/PMS system within 30 min. Moreover, the MnOx-NA/PMS system exhibited impressive stability even after 10 cycles and displayed high anti-interference ability to Cl−, ClO4−, CO32−, SO42−, NO3− and humic acid (HA). In addition, the oxidation system could efficiently remove SMT in different aqueous matrices. Three possible pathways of SMT degradation were proposed according to the LC-MS analysis. Electron paramagnetic resonance (EPR), quenching experiments, and cyclic voltammetry experiments revealed that SMT degradation predominantly occurred through a catalyst-mediated electron transfer pathway. Material characterization and electrochemical impedance spectroscopy (EIS) analysis showed that the derived carbon species strengthened the MnOx-NA's electron-transfer capability and promoted the uniform distribution of MnOx particles on the carbon materials surface, which significantly improved MnOx-NA's PMS activation performance. This study introduces a facile method for the design of Mn/C composites PMS activator and provides theoretical guidance for water pollution remediation.

Plasmonic Probing Single-Cell Bio-Current Waves with a Shrinking Magnetite Nanoprobe.

Probing of the single-cell level extracellular electron transfer highlights the maximum output current for microbial fuel cells (MFCs) at hundreds of femtoampere per cell, which is difficult to achieve by existing devices. Past studies focus on the external factors for boosting charge-extraction efficiency from bacteria. Here, we elucidate the intracellular factors that determine this output limit by monitoring the respiratory-driven shrinking kinetics of a single magnetite nanoprobe immobilized on a single Shewanella oneidensis MR-1 cell with plasmonic imaging. Quantified dissolving of nanoprobes unveils a previously undescribed bio-current fluctuation between 0 and 2.7 fA on a ∼40 min cycle. Simultaneously tracing of endogenous oscillations indicates that the bio-current waves are correlated with the periodic cellular electrokinesis. The unsynchronized electron transfer capability in the cell population results in the mean current of 0.24 fA per cell, significantly smaller than in single cells. It explains why the averaged output current of MFCs cannot reach the measured single-cell currents. This work offers a different perspective to improve the power output by extending the active episodes of the bio-current waves.

Highly Aligned Graphene Oxide for Lithium Storage in Lithium‐Ion Battery Through A Novel Microfluidic Process: The Pulse Freezing

AbstractThe modification of carbon‐based lithium‐ion batteries electrodes is required for the growing need of more reliable electric vehicles. Herein, a new method is introduced to fabricate vertically aligned graphene oxide (GO) films as free‐standing carbon lithium hosts for lithium‐ion batteries with enhanced performance. Vertical alignments are induced of GO in a microfluidic channel by controlling flow rates and patterns of GO suspensions. The vertical alignments are preserved and spontaneously form porous microstructures by Pulse Freezing the GO solutions inside the channel. This combined process results in the increase of levels of microstructure porosity and vertical alignment of GO films. The alignment and porous microstructures increase both electron and ion transfer capabilities across the prepared film. The half‐cell performance of aligned GO films shows a specific capacity of 440 mAh g−1 at a current density of 0.5 A g−1 after 150 cycles. This is a 190% specific capacity increase compared to the performance of a half‐cell prepared with GO without the high level of vertical alignment and microporosity. The significant increase in the value and stability of specific capacity and higher rates of charge transfer favor the promising application of carbon‐based lithium‐ion batteries for electric transportation industries.

Ultrasensitive photoelectrochemical biosensor for DNA 5-methylcytosine analysis based on co-sensitization strategy combined with bridged DNA nanoprobe

Altered DNA methylation in the form of 5-methylcytosine (5-mC) patterns is correlated with disease diagnosis, prognosis, and treatment response. Therefore, accurate analysis of 5-mC is of great significance for the diagnosis of diseases. Here, an efficient enhanced photoelectrochemical (PEC) biosensor was designed for the quantitative analysis of DNA 5-mC based on a cascaded energy level aligned co-sensitization strategy coupling with the bridged DNA nanoprobe (BDN). Firstly, Au nanoparticle/graphite phase carbon nitride/titanium dioxide (AuNPs/g-C3N4@TiO2) nanocomposite was synthesized through in situ growth of AuNPs on g-C3N4@TiO2 surface as a matrix to provide a stable background signal. Next, BDN with a high mass transfer rate synthesized from a pair of DNA tetrahedral as nanomechanical handles was used as a capture probe to bind to the target sequence. The polydopamine nanosphere was applied to load with CdTe QDs (PDANS-CdTe QDs) as a photocurrent label of 5-mC antibodies. When the 5-mC existed, a large number of PDANS-Ab-CdTe QDs were introduced to the electrode surface, the formed CdTe QDs/AuNPs/g-C3N4@TiO2 co-sensitive structure could effectively enhance the electron transfer capability and photocurrent response rate due to the effective cascade energy level arrangement, leading to a significantly enhanced photocurrent signal. The proposed PEC biosensor manifested a wide range from 10−17 M to 10−7 M and a detection limit of 2.2 aM. Meanwhile, the excellent performance indicated the practicability of the designed strategy, thus being capable of the clinical diagnosis of 5-mC.

Enhanced Heterogeneous Fenton-like Process for Sulfamethazine Removal via Dual-Reaction-Center Fe-Mo/rGO Catalyst

A heterogeneous Fenton-like catalyst with single redox site has a rate-limiting step in oxidant activation, which limited its application in wastewater purification. To overcome this, a bimetallic doping strategy was designed to prepare a heterogeneous Fenton-like catalyst (Fe-Mo/rGO) with a double-reaction center. Combined with electrochemical impedance spectroscopy and density functional theory calculation, it was confirmed that the formation of an electron-rich Mo center and an electron-deficient Fe center through the constructed Fe-O-Mo and Mo-S-C bonding bridges induced a higher electron transfer capability in the Fe-Mo/rGO catalyst. The designed Fe-Mo/rGO catalyst exhibited excellent sulfamethazine (SMT) degradation efficiency in a broad pH range (4.8-8.4). The catalytic performance was hardly affected by inorganic anions (Cl-, SO42- and HCO3-) in the complicated and variable water environment. Compared to Fe/rGO and Mo/rGO catalysts, the SMT degradation efficiency increased by about 14.6 and 1.6 times in heterogeneous Fenton-like reaction over Fe-Mo/rGO catalyst. The electron spin resonance and radical scavenger experiments proved that ·O2-/HO2· and 1O2 dominate the SMT removal in the Fe-Mo/rGO/H2O2 system. Fe and Mo, as active centers co-supported on rGO, significantly enhanced the electron transfer between catalyst, oxidant, and pollutants, which accelerated the reactive oxygen species generation and effectively improved the SMT degradation. Our findings offer a novel perspective to enhance the performance of heterogeneous Fenton-like catalysts by accelerating the electron transfer rate in the degradation of organic pollutants.

Cerium‐Modified Mesoporous Antimony Doped Tin Oxide as Intercalation‐Free Charge Storage Layers for Electrochromic Devices

AbstractCharge storage layers are an important component of electrochromic devices, which are expected to exhibit high storage capacity and transparency as well as fast electron transfer rates. However, these layers often rely on the (de)intercalation of ions into the crystal lattice of the material and therefore require optimization to be compatible with non‐intercalating electrolytes. In this report, the post‐modification of mesoporous antimony‐doped tin oxide (ATO) nanoparticle layers with a redox‐active cerium compound is described. In particular, the switching of the Ce3+/Ce4+ couple on the conductive nanoparticle scaffold is demonstrated using tetrabutylammonium perchlorate as a non‐intercalating electrolyte. Remarkably, high storage capacities of up to 27 mC cm−2 and transmittance values of ≈90% are achieved. Variation of the antimony doping concentration revealed that nanoparticle layers doped with 15% Sb exhibit the highest capacity, which can be attributed to increased conductivity in the potential range where the Ce3+ ions are oxidized. Finally, the cerium‐modified ATO films show promising performance as charge storage layers in an electrochromic device with a viologen‐anchored ATO layer as the electrochromic working electrode. Switching times of ≈0.4 s highlight the fast electron transfer capability of the cerium‐decorated ATO layer, even when a non‐intercalating electrolyte is used.

Synthesis and Photocatalytic Applications of Functionalized Carbon Quantum Dots

Abstract Environmental degradation and energy shortages are becoming increasingly important as science and technology advance. Here, we review the photocatalytic approach of functionalized carbon quantum dots (CQDs) along with their up-converted photoluminescence behaviour, as well as their photoinduced electron transfer capabilities, opening a new path to effective metal-free photocatalyst. In this article, we are focusing on the recent invention of CQDs and CQD-based photocatalyst for environmental remediation such as dye degradation, CO2 conversion, and water splitting along with the categorization and synthesis of CQDs-derived photocatalysts, and applications for environmental concerns. Although it is essential to incorporate multiple perspectives, since CQDs and CQD-derived photocatalysts have varied perspectives to tackle unique environmental applications, our analysis is expected to offer additional details on CQD synthesis methods, tuning photocatalytic properties of CQDs with surface groups, and the mechanism of degradation of CQDs and CQD-based photocatalysts.

Highly Stable Two-Dimensional Cluster-Based Ni/Co-Organic Layers for High-Performance Supercapacitors.

Basic requirements for advanced and practical supercapacitors need electrode materials with strong stability, high surface area, well-defined porosity, and enhanced capability of ion insertion and electron transfer. It is worth mentioning that the two-dimensional cluster-based Ni/Co-organic layer (Ni0.7Co0.3-CMOL) inherits high stability from the Kagóme lattice and shows excellent pseudocapacitance behavior. As an optimized atomic composition, this crystalline CMOL exhibits excellent performance and stability both in 1.0 M KOH and All-Solid-State Flexible Asymmetric Supercapacitor (ASCs). The specific capacitance values are 1211 and 394 F g-1 and the energy density is 54.67 Wh kg-1 at 1 A g-1. Good cycling stability is characterized by its capacitance retention, maintained at 92.4% after 5000 cycles in a three-electrode system and 90% after 2000 cycles at 20 A g-1 for assembled All-Solid-State Flexible ASCs. An in situ XRD technique was used in the three-electrode system, which showed that there was no signal of crystalline substance that affected the cyclic stability of the material while charging and discharging. These superior results prove that Ni0.7Co0.3-CMOL is a promising candidate for supercapacitor applications.

Biochar–goethite composites inhibited/enhanced degradation of triphenyl phosphate by activating persulfate: Insights on the mechanism

In this study, the biochar–goethite composites (MBC@FH) were synthesized through co–ball milling and the degradation of triphenyl phosphate (TPhP) was compared in persulfate (PDS) alone system and MBC@FH&PDS systems. The results showed that TPhP can be effectively degraded in PDS alone system and degradation efficiency reached up to 90 % within reaction of 8 h, at a PDS concentration of 10 mM, a reaction temperature of 30 °C and a system pH of 6.12. The obvious degradation can be ascribed to the reactive oxygen species (ROS) generated by self–decompose of PDS, among which 1O2, ∙OH and O2∙− play a major role in the degradation process. Although 350 °C biochar–goethite composites (MBC35@FH) and 800 °C biochar–goethite composites (MBC80@FH) facilitated PDS activation to produce more ROS, the catalytic degradation of TPhP was different in their systems. The degradation of TPhP was inhibited by MBC35@FH due to its stronger adsorption for TPhP, while MBC80@FH promoted TPhP degradation and degradation efficiency was up to 100 % within 6 h. 1O2 and SO4∙− played a stronger degradation role than ∙OH and O2∙− in above systems. The transformation of Fe species, functional groups (oxygen–containing functional groups, pyrrolic nitrogen) and persistent free radicals (PFRs) on the MBC@FH were involved in the PDS activation to produce ROS. Furthermore, MBC80@FH was more capable of activating PDS than MBC35@FH due to its abundant defect sites, larger specific surface area, more PFRs, higher Fe content and stronger electron transfer capability. In addition, seven possible TPhP intermediates were identified and possible degradation pathways of TPhP were proposed accordingly. This study illustrated that not all metallic carbon catalysts are necessarily beneficial for organic contaminants degradation.

Promotion of methane production and degradation of pyrolysis oil during its co-anaerobic digestion process via addition of N-doping hydro-chars

Pyrolysis of wastes usually produces toxic pyrolysis oil (PO), which has complex ingredients, including benzene series and long-chain macromolecule organic pollutants. Co-anaerobic digestion (co-AD) can be an economic and high-efficiency method for PO degradation and recovery of methane simultaneously, but complete degradation of PO has not been achieved yet. Addition of a hydro-char in the process is beneficial to PO degradation and methane production. In this study, to further enhance the effectiveness of the hydro-char, nitrogen (N) was doped into the hydro-char by plasma modification in a NH3 atmosphere; and the effectiveness of the N-doped hydro-chars for promoting PO degradation and methane production during the co-AD process were evaluated. The experimental results indicated that all the hydro-chars can reduce the biotoxicity of the PO, improve its degradation during the co-AD process, and increase the methane yield. Compared with the plain hydro-char (HC), the hydro-chars modified at ambient temperature (HC–NH3–P-25) and at 500 °C (HC–NH3–P-500) can help achieving complete PO degradation and increasing the methane yield more effectively. The anaerobic digestor containing the HC-NH3-P-500 had the highest apparent methane yield (169.03 mLCH4/mLPO) and highest COD removal rate (79.5%). The nitrogen content, specific surface area, and electron transfer capability are found to be the key factors affecting PO degradation and methane yield; and the HC-NH3-P-500 had the highest N-doping, most specific surface area and electron transfer capability, explaining its best performance. The microbial communities of the digestate with the addition of the hydro-chars were founded to be richer with Clostridia and Methanosarcina, which could enhance the electron transfer between different microorganisms and contribute to the PO degradation.

Nitrogen-Doped Graphene Supported α-Co(OH)2 for Sensitive Determination of Adrenaline

For a happy and healthy life, there should have a balance of flight-to-flight hormones, i.e., adrenaline (AD). The necessity of determination of AD is inevitable for the diagnosis of associated diseases with it. For this purpose, N-doped graphene supported α-Co(OH)2 (denoted as NrGO/α-Co(OH)2) was synthesized via a hydrothermal process, where α-Co(OH)2 acted as an active site and NrGO provided a better defective surface for immobilized α-Co(OH)2 nanoparticles. The as-prepared nanocomposite altered the electronic configuration due to its defective nature, which played an important role to increase the stability, surface area and electron transfer capability. As a result, NrGO/α-Co(OH)2 demonstrated remarkable analytical performances toward AD with a lower limit of detection (14.7 nM), wide linear range (0.5–800 μM), and good sensitivity (115.983 μA mM−1 cm−2). The CA response time was obtained as 2.2 s. The proposed sensor showed precious selectivity during AD detection in presence of coexisting biomolecules such as DA, AA, UA, TY, 5-HT, and NE, and 50-fold excess of common ions such as Na+, K+, Ca2+, Mn2+, Fe2+, CO3 2−, and SO4 2−. Furthermore, it also provided long-term stability, good reproducibility and repeatability with practical feasibility in the urine sample. Importantly, the effect of pH was studied in detail on AD oxidation.

Controllable synthesis of FeMn bimetallic ferrocene-based metal-organic frameworks to boost the catalytic efficiency for removal of organic pollutants.

A series of FeMn bimetallic ferrocene-based metal-organic frameworks (FeMn-Fc-MOFs) with various molar ratios of Fe and Mn (1:9, 2:8, 4:6, 6:4) were successfully synthesized using a simple hydrothermal synthesis method and employed as an efficient activator on persulfate (PS) activation for water decontamination. Characterizations demonstrated that Fe and Mn were smoothly introduced into ferrocene-based MOFs and various molar ratios of Fe:Mn had some influence on crystallinity and surface structure of FeMn-Fc-MOFs. Within 120min, Fe4Mn6-Fc-MOFs demonstrated the best catalytic activity among the different molar ratios, and acid orange 7(AO7) degradation rate was up to 92.0%. In addition, electrochemical experiments revealed that Fe4Mn6-Fc-MOFs possessed superior electron transfer capability than other FeMn-Fc-MOFs, leading to better catalytic performance. Moreover, quenching tests and electron paramagnetic resonance (EPR) detection indicated that hydroxyl radicals and sulfate radicals were both responsible for AO7 decomposition. Notably, the redox cycle of Fe(II)/Fe(III) and Mn(II)/Mn(IV) was discovered in the Fe4Mn6-Fc-MOFs/PS system, which was considered as the limiting process for the cleavage of the O-O bond in PS to generate active radicals. Ultimately, the Fe4Mn6-Fc-MOFs exhibits an excellent universality and good cycling stability for 5 continuous runs. This paper broadens the application of ferrocene-based MOFs on heterogeneous PS activation in environmental catalysis.

Synergistic effect of humic substances and bicarbonate on diclofenac degradation by Cu(Ⅱ)/peracetic acid

Bicarbonate (HCO3-) and humic substances (HS), two common water matrix components, were found to exhibit synergistic effect on diclofenac (DCF) degradation by Cu(Ⅱ)/peracetic acid (PAA) process in this work. The mechanism of their impacts on the performance of Cu(Ⅱ)/PAA system was systematically investigated and the reactive species generated in this system was identified. The results revealed that organic radicals (CH3C(O)OO• and CH3C(O)O•) and Cu(Ⅲ) were both generated in HCO3--Cu(Ⅱ)-fulvic acid (FA)/PAA system, and the presence of FA induced Cu(Ⅲ) to become the dominant reactive species for DCF degradation. In comparison with humic acid (HA), FA showed a stronger enhancement effect on DCF removal in HCO3--Cu(Ⅱ)/PAA system, which might be due to its stronger electron transfer capability. However, DCF degradation in HCO3--Cu(Ⅱ)-HS/PAA system with HA-FA mixture was similar to that with HA alone, because Cu(Ⅱ) was prior to be coordinated with HA in HA-FA mixture. The operating parameters (i.e., HCO3-, Cu(Ⅱ) and PAA concentrations) were optimized for DCF degradation. Finally, the efficient DCF degradation in real waters proved that the presence of HS and HCO3- in real waters also strongly enhanced DCF elimination by Cu(Ⅱ)/PAA process. The findings of this work suggested that HCO3- and HS, which are extensively distributed in aquatic environment, can significantly improve the performance of Cu(Ⅱ)/PAA system and this system may be an efficient technology for the removal of refractory pollutants in real waters.

Ultra-trace simultaneous detection of Hg(II), Cd(II), and Cu(II) and mechanism based on Co/CoO/Co3O4 Z-type heterojunctions

Ultra-trace electrochemical determination of various heavy metal ions (HMIs) in water environment is of vital significance. Z-type heterojunction modified electrode materials have attracted vital interest in the electrochemical detection of HMIs because of its valence change and electron transfer capability. Herein, a facile and novel strategy is proposed to synthesize Co/CoO/Co3O4 polyvalent cobalt heterojunction via modified hydrothermal followed microwave carbon bath process. The strong valence change cycle of polyvalent cobalt (Co0, Co2+ and Co3+) plays a significant role in the electrochemical detection for Cd(II), Cu(II) and Hg(II) compared with other cobalt valence states according to the experiment characterizations and density functional theory (DFT) calculation. Co/CoO/Co3O4 exhibits the sensitivity of 4.31 μA/µM for Cd(II), 19.34 μA/µM for Cu(II) and 13.25 μA/µM for Hg(II), which are successfully applied in the real water environment and maintain excellent stability and anti-interference. The results of DFT calculations show that the adsorption energies of Co/CoO/Co3O4 heterojunction for Cu(II), Hg(II) and Cd(II) are − 1.147, − 1.016 and − 0.999 eV, respectively, showing an excellent adsorption capacity for HMIs. This design not only successfully constructs Z-type heterostructures with cobalt multivalence change cycle, but also demonstrates low cost and high efficient electrochemical sensors for simultaneous detection of HMIs.

Se-Doped Ni5P4 Nanocatalysts for High-Efficiency Hydrogen Evolution Reaction

Increasing energy consumption and environmental pollution problems have forced people to turn their attention to the development and utilization of hydrogen energy, which requires that hydrogen energy can be efficiently prepared. However, the sluggish kinetics of hydrogen evolution reaction (HER) requires higher overpotential. It is urgent to design and fabricate catalysts to drive the procedure and decrease the overpotential of HER. It is well known that platinum catalysts are the best for HER, but their high cost limits their wide application. Transition metals such as Fe, Co, Mo and Ni are abundant, and transition metal phosphides are considered as promising HER catalysts. Nevertheless, catalysts in powder form are very easily soluble in the electrolyte, which leads to inferior cycling stability. In this work, Ni5P4 anchored on Ni foam was doped with Se powder. After SEM characterization, the Ni5P4-Se was anchored on Ni foam, which circumvents the use of the conductive additives and binder. The Ni5P4-Se formed a porous nanosheet structure with enhanced electron transfer capability. The prepared Ni5P4-Se exhibited high electrochemical performances. At 10 mA cm−2, the overpotential was only 128 mV and the Tafel slope is 163.14 mV dec−1. Additionally, the overpotential was stabilized at 128 mV for 30 h, suggesting its excellent cycling stability. The results show that Se doping can make the two phases achieve a good synergistic effect, which makes the Ni5P4-Se catalyst display excellent HER catalytic activity and stability.