Electrochemistry Communications最新文献

In quantifying NH₃ and/or NH₄⁺ ions, the wavelength-based spectrochemical methods involving formation of colored products of the Berthelot’s or Nessler reactions might be challenging due to auto-self absorbance, spectral overlap, and background scattering noise. Thus, the current study reports a renewable glassy carbon electrode (GCE) sensing probe combined with Berthelot’s reaction (indophenol formation) and adsorptive square - wave-anodic stripping voltammetry (Ads SWSV) at pH = 10 for detection of NH₃ and/or NH₄⁺ in water. The redox characteristics and the high surface coverage of the oxidation product of indophenol on the sensing platform suggested its use for NH₃ and/or NH₄⁺ detection. The electrochemical sensing probe for NH₄⁺ displayed good linear relationship between 5.56 nM and 55.6 μM of NH₄⁺ with limits of detection (LOD) and quantitation (LOQ) of 4.83 × 10^-9 and 1.47 × 10^-8 M, and sensing probe sensitivity of 1.27μA/μM⁻¹ cm⁻², respectively. The probe was applied for measuring NH₃/NH₄⁺ in fresh and seawater samples, and the results were validated using standard ion chromatography (IC) and micro spectrophotometry assays. The assembled probe was also tolerably selective against interfering of other contaminants in a comparable potential window. Additionally, the probe has exceptional selectivity, long-term stability, and repeatability, and has good capacity to detect NH₃ and/or NH₄⁺ ions with high accuracy (recovery range = 97.14 ± 4.12–102.9 ± 4.7) in environmental water samples. The calculated Student t_exp and F_exp values (n = 5) were less than the tabulated t_tab (2.78) and F_tab (6.39) at 95 % probability (P = 0.05, n = 5). The study offer high reliability towards NH₃ and/or NH₄⁺ detection in complex environments.

Biphasic oxygen reduction and hydrogen evolution are studied for almost two decades, because of favourable overpotential decrease as compared to aqueous solution. Until now, polar solvents (ε > 7) were employed as organic phase in these studies. Here, we applied non polar vegetable oils (rapeseed, linen or sunflower) for biphasic H₂O₂ generation by oxygen reduction. This product was detected at oil|aqueous acid solution interface by scanning electrochemical microscopy, when electron donor – decamethylferrocene, was electrochemically recycled. Ejection of small fraction of decamethylferrocenium cation from oil to aqueous phase was also noticed.

The traditional Pr_0.5Sr_0.5FeO₃ (PSF) cathode is customized with Mn cations to generate the new Pr_0.5Sr_0.5Fe_0.9Mn_0.1O₃ (PSFMn) cathode for proton-conducting solid oxide fuel cells (H-SOFCs). Compared to the PSF oxide, the new PSFMn has a reduced thermal expansion, making it more compatible with electrolytes. Furthermore, Mn-doping enhances oxygen vacancy production in PSF, as revealed by experimental and first-principle calculations. More crucially, doping Mn into PSF improves proton diffusion kinetics, resulting in quicker proton diffusion and surface exchange. As a result, the H-SOFC with the PSFMn cathode achieves an output of 1446 mW cm⁻² at 700 °C, but the PSF cell only achieves fuel cell performance of 1009 mW cm⁻². The fundamental cause of the increased cell performance is the significantly reduced polarization resistance, implying that using the Mn-doping strategy enhances the cathode kinetics of conventional PSF cathodes for H-SOFC.

Anti-perovskite materials such as Li₂(OH)Cl have garnered considerable interest as solid electrolytes due to their numerous advantages. However, the low ionic conductivity of the orthorhombic Li₂(OH)Cl near room temperature presents a significant challenge for the application. In this study, we intricately modulate the −OH content in Li₂(OH)Cl through a controlled heat treatment process. This method effectively increases the cubic phase content and lowers the phase transition temperature, thereby enhancing the ionic conductivity at 30 °C by more than an order of magnitude. Theoretical calculations illustrate that the removal of −OH content significantly reduces the barrier for phase transition, leading to substantial alterations in the Li-ion transport pathway and migration barrier. Furthermore, LiHClO-600 demonstrates exceptional resistance to lithium reduction and is compatible with lithium metal and LiFePO₄, rendering it a viable solid electrolyte for batteries. Both experimental findings and theoretical calculations cohesively highlight the pivotal role of −OH content in driving phase transition and facilitating Li-ion transport in anti-perovskite solid electrolytes, paving the way for their potential utilization in all-solid-state batteries.

Thermo-electrochemical cells (or thermogalvanic cells or thermocells, TECs) have gained attention as devices able to convert low temperature heat into electricity. Within TECs, Pt is one of the most employed electrodes, since it exhibits a fast transfer of electrons with the redox couple in the electrolyte. However, its high price represents a serious drawback. Here, we analyze the use of nanostructured and porous antimony-doped tin oxide (Sb:SnO₂) as electrode material. Electrodes of different thickness (320, 550 and 1550 nm) were fabricated by spin coating to study the effect of the electrode area in contact with the electrolyte. F:SnO₂ (FTO) glass was used as a substrate and the typical 0.4 M potassium ferro/ferricyanide aqueous solution served as electrolyte. An impedance spectroscopy analysis under operating conditions (10 K temperature difference) showed that the Sb:SnO₂ electrodes exhibit the same excellent kinetics as Pt for all the different thickness. On the other hand, the power output density was thickness independent, since the temperature coefficients and the series and mass-transport resistances were similar, leading to no performance improvements when the electrode area in contact with the electrolyte was significantly increased. Finally, the Carnot-related efficiencies estimated for the Sb:SnO₂ cells were in the same order of magnitude as for Pt electrodes. These results open the possibility to use Sb:SnO₂ as a suitable electrode in TECs at low cost.

In this work, TiO₂ was firmly attached on freestanding graphene (Gr, rather than graphene oxide or reduced graphene oxide) nanosheets (Gr@e-TiO₂) by a novel electrodeposition method. The morphology, crystal structure, band gap characteristics, optical properties and photoelectric properties were systematically investigated. It is indicated that the absorption of visible light increased and the recombination of photogenerated electron-hole pairs decreased for the as-obtained Gr@e-TiO₂. Compared with pure TiO₂ as well as GO (graphene oxide)@h-TiO₂ prepared by conventional hydrothermal method, Gr@e-TiO₂ exhibited a more negative open circuit potential and higher photocurrent density for 304SS protection. The enhanced photocathodic protection performance of Gr@e-TiO₂ can be attributed to the large specific surface area and good charge transport efficiency of graphene.

The biocurrent generated by soil extracellular electron transfer (EET) partly drives biogeochemical cycles and controls soil quality. However, it is unclear how the soil abiotic and biotic conditions affect the biocurrent conduction. In this study, the response relationship of soil microenvironment and in-situ biocurrent was studied. The results showed that red soil exhibited the optimal electron transfer efficiency, as evidenced by the maximum current density and accumulated charge output, with increments of 56–93 % and 80–2800 %, respectively, compared with the other five types of soils. Soil physicochemical properties were the most important factor on the biocurrent generation, and further the quantity and bioavailability of dissolved organic matter, NH₄⁺-N content, and lower pH were predictive indicators for the exoelectrogenic processes of soils. In addition, the high soil biocurrent was likely determined by a complex synergistic network of the transformation of carbon and nitrogen, electroactive bacteria involving the functions of cell wall/membrane and cytochrome enzyme metabolism and transport related EET process. Overall, we provide an insight into the relationship among soil biocurrent conduction, physicochemical properties, bacteria community and metabolic function, and a support for bioelectrochemical technology application.

The research on lithium-sulfur batteries (LSBs) addresses the challenges of sulfur's insulating properties and the 'shuttle effect' of lithium polysulfides (LiPSs) hindering their commercialization. The introduction of a phosphorous-modified mesoporous Titanium Nitride (TiN) interlayer for the S@MWCNTs cathode demonstrates significant advancements in enhancing conductivity and enabling greater sulfur loading. This modification minimizes the LiPS's 'shuttle effect' through robust chemical bonds with phosphorous loading, leading to superior electrochemical performance. Electrochemical analyses reveal that the phosphorous-modified TiN offers a greater number of active sites for catalyzing redox reactions of the sulfur cathode. The phosphorous-modified mesoporous titanium nitride (P-TiN) interlayer exhibits impressive electrochemical performance, delivering a capacity of 358 mAh g⁻¹ after 320 cycles at 0.1 C and demonstrating high-rate performance of 380 mAh g⁻¹ at 1 C.

Transition metal dichalcogenide (TMD) heterostructures have been discovered to have improved catalytic activity towards the hydrogen evolution reaction (HER). This study explores the stability and HER catalytic activity including reaction kinetics of heterolayers of different TMDs (MoS₂, MoSe₂ and WS₂). The stability of the heterolayers varied with those having an overlayer of electrodeposited MoS₂ being more stable as compared to those with MoSe₂ overlayer which degraded with each scan in acidic media. Investigation into the HER kinetics of the heterolayers involved Tafel analysis and electrochemical rate constant calculation. There was an improvement in Tafel values calculated in comparison to reported values for these heterolayers. WS₂/MoS₂ and MoSe₂/MoS₂ heterolayers registered rate constants of (3.20 ± 0.10) × 10⁻⁴ cm s⁻¹ and (1.73 ± 0.03) × 10⁻⁴ cm s⁻¹ respectively, which was an improvement of up to an order of magnitude compared to the reported rate constant of electrodeposited MoS₂ of (3.17 ± 0.30) × 10⁻⁵ cm s⁻¹. All this highlights the improved HER catalytic activity of the heterolayers.

In this study, Ni-GQDs nanocomposite coatings were prepared by double-pulse electrodeposition under supercritical CO₂ with graphene quantum dots (GQDs) as the second phase additive. The effects of supercritical CO₂ conditions and reverse pulse current density on microstructure, crystal orientation, grain size, GQDs quality, mechanical properties, and corrosion resistance of Ni-GQDs nanocomposite coatings were investigated. The results show that when the reverse pulse current density is 0.8 A /dm², the surface of Ni-GQDs-Ⅱ nanocomposite coating is compact and flat, GQDs is uniformly dispersed in the coating, and GQDs is closely bound to Ni grains. Compared with the coating prepared at normal temperature and pressure. The grain size of the Ni-GQDs-Ⅱ nanocomposite coating is 4.58 nm, and the grain size is reduced by 75.3 %. The quality of GQDs in the coating was improved. The coating hardness is 867.22 HV, which is significantly increased by 53.7 %. The roughness is 0.236 μm, which is significantly reduced by 37.2 %. The friction coefficient and volume wear were 0.262 and 3.395 × 10⁷ μm³, respectively, which were significantly reduced by 27.4 % and 57.9 %. After electrochemical corrosion, the self-corrosion voltage of the coating was −139 mV, and the self-corrosion current density was 3.19 × 10⁻⁷ A/cm². The self-corrosion voltage was significantly increased by 61.2 %, and the self-corrosion current density was significantly decreased by 71.2 %. The R_ct value and N_dl value of the coating are 31594.53 Ω·cm² and 0.862, respectively. Significantly increased by 226.2 % and 67.1 %, respectively. The coating has excellent mechanical properties and corrosion resistance.