Electrochemistry Communications最新文献

The present study focuses on the highly catalytic double-perovskite Sr₂FeMo_0.65Ni_0.35O_6−δ (SFMNi) fuel electrode material for Solid Oxide Electrolysis Cells (SOECs). The electrolyte-supported single button cells with the highly active SFMNi fuel electrode were electrochemically characterized between 900 °C down to 750 °C in steam and co-electrolysis conditions using DC- and AC-techniques. The cells achieved current densities of −1.62 A cm⁻² and −1.74 A cm⁻² at 900 °C under steam and co-electrolysis conditions, respectively, exceeding the performance of cells with Ni-8YSZ fuel electrodes by ∼65–79 % and Ni-GDC fuel electrodes by 24–28 %. The post-test SEM-EDX analyses of the as-prepared and tested cells’ cross-section showed increased pore formation and particle growth of the SFMNi fuel electrode after testing in the humidified atmosphere for 500 h.

A catalytic pseudo-8-electron redox reaction of sulfur is achieved by facilitating the disproportionation of high-order polysulfide ions in a Li-Sulfur battery. Electrochemically generated polysulfide ions (S_x^2-, where 3 < x < 7) undergo rapid disproportionation into elemental sulfur (S₈) and Li₂S₂, catalyzed by a bifunctional carbon host/catalyst. The overall catalytic redox reaction at the sulfur cathode is represented as $S_8+{8Li}^{+}+8e\rightleftharpoons {4Li}_2{S}_2$. In contrast to physical or chemical confinement methods for polysulfide ions, this approach remediates the shuttle effect by swiftly converting soluble polysulfides in the electrolyte to elemental sulfur and insoluble Li₂S₂ within the cathode matrix. As a result, the adverse chemical interaction between dissolved polysulfides and the Li anode is mitigated.

The medium-entropy perovskite oxide Bi_0.5Sr_0.5Fe_0.85Nb_0.05Ta_0.05Sb_0.05O_3–δ (BSFNTS) is evaluated as a potential cathode catalyst for solid oxide fuel cells (SOFCs). The crystal structure, electrocatalytic activity, oxygen reduction kinetics, and CO₂ tolerance are systematically investigated. At 700 °C, the BSFNTS cathode exhibits excellent electrochemical performance with a polarization resistance as low as 0.095 Ω cm². The maximal power density of the fuel cell with the BSFNTS cathode is 900 mW cm⁻². Furthermore, the rate control step for the oxygen reduction reaction (ORR) of the electrode is primarily identified as the adsorbed and diffusion process of the molecule oxygen. The BSFNTS electrode presents excellent CO₂ tolerance and durability in a CO₂-containing atmosphere, which is related to the high acidity of Bi, Nb, Ta, and Sb cations and the larger average bonding energy of BSFNTS. The preliminary results indicate that BSFNTS medium-entropy oxide is an attractive cathode electrocatalyst for SOFCs.

Because of the presence of electrochemically inactive C-F₂ bond and poor electronic conductivity of C-F, the discharge performance of lithium fluorocarbon (Li/CF_x) batteries is limited, despite their extensive use in commercial fields. In this study, dimethyl silicone oil/polyethylene glycol was adopted to improve the performance of CF_x through relatively low temperature (350 °C) defluorination and carbon coating. The uniform mixing of dimethyl silicone oil with CF_x and the subsequent gas–solid reaction enables mild defluorination, transforming C-F₂ into semi-ionic C-F with high conductivity. Furthermore, this dimethyl silicone oil/ polyethylene glycol treated CF_x under 350 °C prevent the thermal decomposition of C-F during both of the defluorination and carbon coating process, resulting in improving the electrical performance and capacity protection of CF_x. Specifically, the modified CF_x cathode exhibits a 2.7 V discharge platform, a discharge capacity of 859.1 mAh/g and the energy density of 1889.7 Wh kg⁻¹ at 0.01C. This approach allows for large scale adjustments of CF_x with excellent performance, making it easy to industrialization.

Electrochemical nitrogen reduction reaction (eNRR) is recognized as an alternative green approach to the traditional energy-demanding and fossil-based catalytic processes (e.g. Haber Bosch). In this study, we implement eNRR in a proton exchange membrane (PEM) water electrolyzer in which nitrogen (N₂) is fed in the cathode. This operation mode has been suggested as a way to overcome mass transfer limitations, however, there is a lack of developed evaluation protocols for appropriate product identification. Herein, we exemplify the spirit of the evaluation protocols for gas phase operation at the device level with a combination of online product analysis and isotopic labeling. Our protocol involves control experiments by replacing the cathodic N₂ feed with (i) inert gas (i.e. Ar) and (ii) isotopic labeled ¹⁵N₂ and by replacing the anodic water feed with isotopic labeled D₂O. Taking advantage of the gas phase operation in the cathode product analysis is realized with online techniques i.e. quadrupole mass-spectrometer (QMS) and Fourier transform infrared (FTIR) spectrometer. This allows us to verify the production of diazene (N₂H₂) resulted from genuine N₂ reduction, rather than from nitrogen-containing contaminants. Our methodology provides a pathway for how the false positive results can be eliminated in the gas phase study and a platform for follow-up studies using promising or exotic catalysts in the cathode, especially to validate the eNRR products or discover more products.

Direct electrochemical ammonia oxidation reaction (AOR) using NiCu-based anodes is effective in removing ammonia from wastewater. However, this type of anode frequently produces undesired byproducts NO₃⁻. Here, we investigated three configurations of novel Cu/Ti cathodes (Cu(1 1 1)/Ti, Cu(2 0 0)/Ti, Cu(2 2 0)/Ti) coupled with Cu/Ni foam (Cu/NF) anode to enhance N₂ selectivity (SN₂) in a direct ammonia electrolysis cell. Cu(2 0 0)/Ti cathode improved SN₂ from 35 % (bare Ti cathode) to 60 % and it achieved 10–15 % higher SN₂ compared to Cu(1 1 1)/Ti and Cu(2 2 0)/Ti. The improvement of SN₂ on Cu(2 0 0) facet was ascribed to the high nitrate electroreduction activity and its conversion to N₂. In real wastewater, Cu/NF anode-Cu(2 0 0)/Ti cathode paired electrolysis system demonstrated its excellent capability of 88 % NH₃ removal with 95 % SN₂. Our electrolysis system was capable to maintain the residual NH₃-N and the NO₃-N below 8 mg L⁻¹, meeting effluent discharge standards. Our findings highlighted the importance of the control of Cu cathode facet orientations for an efficient elimination of NO₃^– and improvement of N₂ production during direct ammonia electrolysis.

Based on the wide interlayer distance for ions diffusion, iron (II) oxalate exhibits excellent lithium storage ability. However, the local deposition of metallic nanoparticles of Fe⁰ leads to low electrochemical reactivity, which hinders the actual application of FeC₂O₄ in large current regions (>5C). To solve this problem, a strong cationic polymeric electrolyte, polyelectrolyte diallyl dimethyl ammonium (PDDA), was introduced to construct a [FeC₂O₄(PDDA)]⁺ ligand. By single-polymerization‐induced electrostatic self-assembly, the [FeC₂O₄(PDDA)]⁺ ligand was combined with the surface-charged rGO to produce a FeC₂O₄/rGO material. It is proved that the rGO carrier improves the interparticle conductivity, electrochemical activity and structure stability of the iron (II) oxalate particles, ensuring the stability of Li || FeC₂O₄/rGO battery at a rapid charging rate of 20C (8 A g⁻¹) for more than 500 cycles (with the special capacity of 713 mAh g⁻¹). Compared with FeC₂O₄ electrode, owning to high reactivity of rGO and continuously activating on the nanoscale Fe metal generated at ∼0.75 V, FeC₂O₄/rGO shows higher electrochemical activity of conversion reaction in the first 50 cycles and better reversibility in the rate charge–discharge test (the capacity rapidly increased to 1158.8 mAh g⁻¹ after 20C cycles). This work reveals how the structural design of conducting and supporting the carrier can achieve fast charging for iron (II) oxalate lithium-ion batteries.

We report nitrogen-doped biomass-derived porous carbon materials with great performance for the Oxygen Reduction Reaction (ORR) in alkaline media. The level of nitrogen doping in a simple pyrolysis of corncob (CC) was varied systematically, a 1:1 CC:urea ratio (CC_1U) gave the best performance in terms of onset potential (E_onset = 0.97 V vs. RHE), maximum current density (j_max = -3.22 mA cm⁻²), hydroperoxide ion yield (%HO₂^– = 1.18 % at 0.5 V), and electron transfer number (n = 3.86 at 0.5 V). Unexpectedly, for higher CC:urea ratios the doping decreases, instead of plateauing, with lower concentration of C-N sites and more sp² sites as determined by XPS, as well as lower specific surface area (SSA), while increasing both porosity and carbon (0 0 2) interplanar distance (d_(0 0 2)). These materials should be durable and robust, since their performance actually improved after accelerated degradation tests. This study proves that renewable “waste” can be upconverted into metal-free electrocatalysts for electrochemical energy conversion technologies and emphasizes the need for studying and controlling doping levels to enhance performance.

In this work, we study the influence of cation concentration and identity on the hydrogen evolution reaction (HER) on polycrystalline platinum (Pt) electrode in pH 3 electrolytes. Our observations indicate that cations in the electrolyte do not affect proton reduction at low potentials. However, an increase in cation concentration significantly enhances water reduction. Simultaneously, we identify a non-negligible migration current under mass transport limited conditions in electrolytes with low cation concentration. To separate migration effects from specific cation-promotion effects on HER, we carried out further experiments with electrolytes with mixtures of Li⁺ and K⁺ cations. Our results show that, adding strongly hydrated cations (Li⁺) to a K⁺-containing electrolyte leads to a less negative onset potential of water reduction. Interfacial pH measurements reveal a same interfacial pH at the platinum electrode in pH 3 in the presence of 80 mM LiClO₄ and KClO₄, respectively, at potentials where water reduction occurs. Based on these results, we suggest that under the current conditions, the strongly hydrated cations (Li⁺) promote water dissociation on the Pt electrode more favorably in comparison with the more weakly hydrated cations (K⁺), and that this promotion is not related to a local pH effect.

We report on the colloidal synthesis of Cu₃VS₄ nanocrystals as an earth abundant anode material for sodium-ion battery applications. The nanocrystals were structurally characterized prior to testing in half-cells, where they displayed excellent cycling stability up to 1000 cycles, demonstrating the potential of colloidally synthesised materials for sustainable battery applications.