Optimum Current Density Research Articles

Suppressing surface segregation by introducing lanthanides to enhance high-temperature oxygen evolution reaction activity and durability

Abstract Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) is a conventional anode material for solid oxide electrolysis cells (SOECs) to catalyze oxygen evolution reactions (OERs). However, the inferior chemical stability of BSCF results in severe surface segregation and performance degradation under high temperatures. A critical challenge lies in alleviating surface segregation and preserving the high OER performance of BSCF anodes. Herein, lanthanides are introduced to substitute the Ba in BSCF, labeled as Ln0.5Sr0.5Co0.8Fe0.2O3−δ (LnSCF, Ln = La, Pr, Nd, Sm), to regulate its stability and performance. The introduction of La and Pr effectively enhances stability, suppresses surface segregation and maintains high OER activity. Continuous lattice oxygen loss and Co ion oxidation of LnSCF are demonstrated upon annealing in oxidizing atmosphere; thus, we propose that surface segregation is a self-regulation mechanism of perovskite lattice to tolerant oxidizing atmosphere. Perovskite oxides maintain structurally stable via decreasing A-site valence state and forming surface segregation. SOECs with La0.5Sr0.5Co0.8Fe0.2O3−δ anodes deliver an optimal current density of 1.69 A cm−2 at 1.6 V and stability for CO2 electrolysis at 800 °C, shedding light on designing advanced catalysts for high-temperature OER.

Determination of performance properties of galvanic coatings based on cobalt

Abstract. Problem. An effective solution to the problem of the durability of construction materials is the application of protective coatings, which allow tosignificantly expand the scope of use and service life of products. The purpose of the work was to determine the performance characteristics of electrolytic coatings with Co-Ni-Zr alloy, namely adhesion and microhardness. Methodology The microhardness of the coatings was determined by the indentation depth of the diamond pyramid. Coating adhesion was determined by the fracture method. The chemical composition of the obtained coatings was determined by the X-ray fluorescence method using the SPRUT portable spectrometer. The analysis was carried out at least in 3 points with subsequent averaging of the obtained values. Electrodeposition was carried out with a unipolar current in stationary and pulsed modes (ti/tр=2/2) while varying the current density. Originality. There are no signs of delamination of the coatings on the sandpaper, which emphasizes strong adhesion to the base. The results of metallographic studies proved that Co-Ni-Zr coatings have good adhesion to the substrate material and retain it under mechanical loads. The highest value of microhardness – 850.0 MPa was obtained in the galvanostatic mode at i = = 6 A/dm2, while the zirconium content in the alloy is 1.5 wt.%. From the results of the experiments, it can be concluded that the zirconium content does not affect the microhardness of the Co-Ni-Zr coating. When the current density increases, the microhardness of the deposit decreases, which can be explained by reaching the maximum density of the deposition current. The optimal deposition current density for the galvanostatic mode is 6 A/dm2, pulsed 6 A/dm2 for obtaining coatings with high microhardness

Development of engineering coating based on alumina nanoparticles incorporated into a Ni-Co alloy matrix: Effect of current density and alumina bath loading on microstructure and electrochemical corrosion behavior

The construction of electrodeposited coatings (EDCs) with enhanced microstructural characteristics and superior electrochemical corrosion behavior is of enduring concern for the industrial applications. In this study, alumina (Al2O3) nanoparticles were incorporated into a Ni-Co alloy matrix to improve its morphological and electrochemical behaviors. The primary objective was to assess the impact of varying electrodeposition current densities (20, 40, and 60 mA/m2) and different contents of alumina (3, 5, and 7 g/L) on the properties of a ternary Ni-Co-Al2O3 composite coating. EDX analysis was employed to investigate the effects of deposition current density and alumina bath loading on cobalt/nickel (Co/Ni) ratio and alumina content in the coatings. The results revealed that both the Co/Ni ratio and alumina content in the coatings increased with increasing current density and bath loading, but only up to certain thresholds (40 mA/m2 and 5 g/L). XRD analysis was conducted to assess the phase composition, crystal structure, crystallite size values, and preferred orientation of the fabricated EDCs. The mechanical properties of the deposited coatings were also evaluated using Vickers microhardness testing. The electrochemical corrosion behavior of the as-prepared EDCs was assessed using potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS) techniques. The 40 mA/cm2 and 5 g/L samples exhibited lower corrosion current density (jcorr), higher charge transfer resistance (Rct), and lower double layer capacitance (CPEdl) values, suggesting that the increased cobalt and alumina particles in the coatings improved the corrosion resistance. Consequently, the optimal current density and alumina bath content for achieving the most favorable properties were found to be 40 mA/m2 and 5 g/L, respectively.

Electrochemical Characterization of Silver and Iron Ions in Choline Chloride-Ethylene Glycol DES Electrolyte

Solar energy is growing to be an important source of renewable energy in the world, and the need of a recycling process to recover the strategic materials used for this technology is crucial. A route to recover Si and Ag from end-of-life photovoltaic (PV) cells as well as scrap from PV manufacturing using a Deep Eutectic Solvent (DES) have been proposed and developed as part of the PHOTORAMA project. The suggested ionometallurgical route uses a DES solution with FeCl3 as oxidizing agent to leach silver and separate it from Si, before recovering Ag metal by electrowinning (EW) from the DES-based electrolyte.Choline Chloride (ChCl)-Ethylene Glycol (EG) DES mixtures, often referred to as ethaline, in composition 1:2 molar ratio was identified as the preferred DES-system to be used for leaching and subsequent EW. As such, the DES leachate used as electrolyte in the EW step, should ideally consist of Ag(I) and Fe(II) dissolved in the DES. The goal of this work was to carry out electrochemical characterization of the electrochemical systems and understand if the presence of soluble iron species may affect the silver deposition.Model electrolyte solutions were produced by dissolving AgCl, FeCl2, and FeCl3·6H2O in the DES mixture. Electrochemical investigations were carried out at 60 °C by cyclic voltammetry (CV) and chronoamperometry (CA) using a 3-electrode setup. Moreover, silver deposits were obtained by potentiostatic or galvanostatic electrolysis, and subsequently analysed by Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS).Cyclic voltammograms obtained using a Pt-wire with a scan rate of 200 mV/s, show well defined Ag(I)/Ag and Fe(III)/Fe(II) electrochemical systems. The deposition of metallic Fe was found to be close to the cathodic decomposition of the DES electrolyte. High quality silver deposits were obtained by choosing optimal deposition potentials or current densities. SEM-EDS analysis of the silver deposits obtained on Pt, silver, and stainless steel (316L) substrates showed a nice, dense layer of Ag crystals with a microstructure of truncated octahedrons, with a purity of 96-98 wt%. The impurities were identified as C, O or Cl and probably stemmed from the DES electrolyte remains.Based on the electrochemical characterization of the DES systems, and the analysis of the obtained silver deposits, the concept proposed for the recovery of metals in the PHOTORAMA project was found to be suitable. Water added to the DES (up to 10 wt%), which may be stemmed from the crystal water of the oxidant added, or absorbed from air, gave improved kinetics. The presence of excess of Fe(III), which could arise from incomplete leaching reaction, had the obvious negative effect on the current efficiency of the Ag(I) reduction reaction, but had no effect on the silver morphology or purity of the obtained deposit.AcknowledgementsThis project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 958223. The content in this publication reflects only the views of the authors. The European Commission is not responsible for any use that may be made of the information it contains. Figure 1

Insights from the Systems Scale to Design Practical CO2 Electrolyzers

Electrochemical CO2 reduction (CO2R) can convert captured CO2 into chemical feedstocks and fuels using renewable electricity and water, but scaleup has been limited. To guide targets that set the direction of research in the field, we connect a systems-level perspective on CO2R with electrolyzer design. A physics-informed technoeconomic assessment can highlight the sensitivity of overall process cost towards improvements at the electrolyzer scale, identifying the most impactful opportunities to improve performance. The assessment confirms the importance of better materials (membranes, catalysts), which has been the focus of the field, and that electricity prices are currently too high for economical CO2R. However, we find a critical and overlooked need for improved reactor design to make CO2R economically viable. Analyzing the separations needed for state-of-the-art CO2R electrolyzers shows that maximizing single-pass conversion comes at the cost of product composition and process energy. This is because electrolyzers increase conversion by restricting feed flow rate or by using strongly acidic electrolytes. Both these conditions promote the HER side reaction, wasting expensive electricity on making byproducts.Our work has shown the tradeoff between single-pass conversion and selectivity for CO2 electrolyzers, a limitation that arises directly from current reactor design. Due to selectivity loss, we show that increasing single-pass conversion beyond ~10% increases process cost for current electrolyzer designs and process costs. Since the relationship between selectivity and single-pass conversion comes from the plug-flow channel design, we call on the field to investigate reactor designs that modify this crucial handle on CO2R cost by improving the availability of CO2 to the catalyst surface. On the other hand, we show that mitigating the “carbonate problem” leads to relatively small improvements in cost for relevant electrolytes. Moreover, operation at high current density (>1 A/cm2)has been repeatedly proposed as a target for the field. Such high currents lead to a tradeoff between capex and utility cost at a much lower current density than has been proposed. At current electricity prices, the optimal total current density is <300 mA/cm2. Therefore, high operating currents will worsen process costs, unless accompanied by much lower electricity costs or considerable improvement in the full-cell polarization curve for CO2R in membrane electrode assemblies.

Influence of Annealing Temperature on the OER Activity of NiO(111) Nanosheets Prepared via Microwave and Solvothermal Synthesis Approaches.

Earth-abundant transition metal oxides are promising alternatives to precious metal oxides as electrocatalysts for the oxygen evolution reaction (OER) and are intensively investigated for alkaline water electrolysis. OER electrocatalysis, like most other catalytic reactions, is surface-initiated, and the catalyst performance is fundamentally determined by the surface properties. Most transition metal oxide catalysts show OER activities that depend on the predominantly exposed crystal facets/surface structure. Therefore, the design of synthetic strategies to obtain the most active crystal facets is of significant research interest. In this work, rock salt NiO OER catalysts with (111) predominantly exposed facets were synthesized by a solvothermal (ST) method either heated under supercritical or microwave-assisted (MW) conditions. Particular emphasis was placed on the influence of the post annealing temperature on the structural configuration and OER activity to compare their catalytic performances. The as-prepared electrocatalysts are pure α-Ni hydroxides which were converted to rock salt NiO (111) nanosheets with hexagonal pores after heat treatment at different temperatures. The OER activity of the electrodes has been evaluated in 0.1 M KOH using geometric and intrinsic current densities via normalization by the disk area and BET area, respectively. The lowest overpotential at a geometric current density of 10 mA/cm2 is found for samples pretreated by heating between 400 and 500 °C with a catalyst loading of 115 μg/cm2. Despite the very similar nature of the catalysts obtained from the two methods, the ST electrodes show a higher geometric and intrinsic current density for 500 °C pretreatment. The MW electrodes, however, achieve an optimal geometric current density for 400 °C pretreatment, while their intrinsic current density requires pretreatment over 600 °C. Interestingly, pretreated electrodes show consistently higher OER activity as compared to the poorly crystalline/less ordered hydroxide as-prepared electrocatalysts. Thus, our study highlights the importance of the synthesis method and pretreatment at an optimal temperature.

Application of Hydrogen Spillover to Enhance Alkaline Hydrogen Evolution Reaction

AbstractAlkaline water splitting has shown great potential for industrial‐scale hydrogen production. However, its broad application is constrained by hydrogen evolution reaction (HER) electrocatalysts, which struggle to achieve optimal current density at low overpotential. The utilization of the hydrogen spillover effect to augment the performance of HER represents a burgeoning area of research. Although previous studies mainly focused on hydrogen spillover in acidic media, the latest studies have shown that hydrogen spillover also exists under alkaline conditions, and its role in improving HER performance cannot be ignored. This review examines the mechanisms of HER under acidic and alkaline conditions, elucidating the distinctive behavior of hydrogen spillover in these environments and its influence on catalytic processes. At the same time hydrogen spillover characterization methods are systematically summarized, these technologies for understanding and control of hydrogen release process provides strong support. Finally, the recent electrocatalysts that enhance the catalytic performance of alkaline HER by hydrogen spillover effect are comprehensively sorted out and summarized. This review not only demonstrate the practical value of hydrogen spillover under alkaline conditions, but also provide new directions for future design and optimization of electrocatalysts.

Calcium titanate corrosion inhibitor enabling carbon as inert anode for oxygen evolution in molten chlorides

The corrosion inhibition efficacy of titanate (CaTiO3) for carbon anodes in molten salts was investigated through various analytical techniques, including linear sweep voltammetry, X-ray diffraction, scanning electron microscopy, and energy dispersion spectroscopy. The results demonstrate that the addition of CaTiO3 corrosion inhibitor efficiently passivates the carbon anode and leads to the formation of a dense CaTiO3 layer during the electrolysis process in molten CaCl2−CaO. Subsequently, the passivated carbon anode effectively undergoes the oxygen evolution reaction, with an optimal current density for passivation identified at 400 mA/cm2. Comprehensive investigations, including CaTiO3 solubility tests in molten CaCl2−CaO and numerical modeling of the stability of complex ionic structures, provide compelling evidence supporting “complexation−precipitation” passivation mechanism. This mechanism involves the initial formation of a complex containing TiO2·nCaO by CaTiO3 and CaO, which subsequently decomposes to yield CaTiO3, firmly coating the surface of the carbon anode. In practical applications, the integration of CaTiO3 corrosion inhibitor with the carbon anode leads to the successful preparation of the FeCoNiCrMn high-entropy alloy without carbon contamination in the molten CaCl2−CaO.

A novel dual functional gradient Zn(O,S)/Mg electron-selective contact for dopant‐free silicon solar cells with efficiencies approaching 21 %

Dopant-free carrier-selective contacts have the potential to mitigate or eliminate parasitic absorption, auger recombination losses, etc. Therefore, the vigorous development of dopant-free carrier-selective contact materials is an important way to enhance the performance of crystalline silicon (c-Si) photovoltaics. This study presents the concept of magnetron sputtering gradient deposited zinc oxide (Gd-Zn(O,S)) combined with a low work function magnesium metal layer. Subsequently, the Gd-Zn(O,S)/Mg bifunctional layer was further investigated and optimised to determine its suitability as a contact layer for electron transfer in c-Si solar cells. This strategy simultaneously enables a good passivation and a low contact resistance. The c-Si(n)/a-Si:H(i)/Gd-Zn(O,S)/Mg devices are constructed and achieved an optimal contact recombination current density (J0) of approximately 1.51 fA cm−2, along with a minimum ρc of approximately 35.89 mΩ.cm2. As a consequence, the power conversion efficiency of a prototype silicon heterojunction solar cell is 20.92 %. This study demonstrates that the strategy of replacing the a-Si:H(n) electron transport layer with Gd-Zn(O,S) is an effective approach for improving the SHJ cell. This study also provides new perspectives for designing novel dopant-free carrier-selective contact structures.

Advancing the assessment of ICCP efficiency for steel reinforcement: A novel electrochemical investigation

Impressed current cathodic protection (ICCP) is an electrochemical technique employed to mitigate corrosion. The evaluation of its effectiveness has traditionally relied on qualitative criteria such as protection potential and potential decay. This study proposes a novel electrochemical setup to enable measurements during current-controlled ICCP treatment. The experimental outcomes demonstrate that the proposed approach, in conjunction with protection potential analysis, allows for the quantitative determination of the optimal ICCP current density. As the protection current density increased, the fitted charge transfer resistance (Rct) initially showed an upward trend, followed by a gradual decline. To accurately interpret the results, it is crucial to discern whether the Rct values correspond to oxidation reactions (referred to as corrosion reactions in this context) or reduction reactions. Furthermore, it was observed that the optimal current density was closely associated with the severity of initial corrosion, in line with previous findings. This consistency serves to further validate the efficacy of the proposed method.

Controlling coating thickness distribution for a complex geometry with the help of simulation

This paper aims to develop a proper and valid simulation model for electroplating complex geometries. Since many variables influence the quality of the deposited coating and its thickness distribution, it is challenging to conduct efficient research only through experiments. In contrast, simulation can be an efficient way to optimize the electroplating experiments. Despite its potential, simulation has seen limited commercial use in the electroplating industry due to its inherent complexity and difficulty in achieving accurate precision for intricate geometries. The present study addresses the aspects that can enhance the electroplating simulation’s accuracy, which has been typically overlooked in the literature, such as the effect of current efficiency and its dependency on the current density, the input data for the electrode kinetics, the surface topology changes, and the differences between 2 and 3D simulations. The simulation model was validated by experimental results related to the coating thickness of Ni plating on a T-joint geometry. The results showed good agreement with the experimental ones, confirming the model’s ability to precisely predict the coating thickness and distribution and promote its broader utilization in the industry. Finally, the developed model was used to determine the optimal current density regime for achieving uniform coating thickness distribution on a T-joint sample.

Removal of Ammonia and Colour from Landfill Leachate using Integrated Electrocoagulation-Zeolite Adsorption Processes

The amount of waste generated in Malaysia had increased annually due to both economic and population accelerations. This resulted in an increase in leachate production that contains a high amount of ammonia nitrogen (NH3-N) and colour, which is a severe problem for both environments as well as for human health. Therefore, this study aimed to determine the potential of Electrocoagulation (EC) – zeolite adsorption for removing NH3-N and colour from landfill leachate. In the experimental works, two batch studies consist of batch EC using aluminium (Al) cylindrical electrode and batch adsorption study using clinoptilolite zeolites adsorbent were conducted using leachate sample collected from Pulau Burung Sanitary Landfill (PBSL). The batch EC experiment was carried out to determine the optimum removal of NH3-N and colour by the effect of current density (7 - 35 mA/mm2), initial pH (5 - 9), electrolysis time (0 - 90 minutes) and inter-electrode distance (5 - 25 mm). An integrated EC - zeolite adsorption was carried out under the optimum condition of 2.0 g/150 mL adsorbent dosage, contact time of 100 minutes and an initial pH value of 8. Based on the experiment, almost 50% of NH3-N and 95% of colour were removed using a single EC under the optimum current density of 14.0 mA/mm2, pH 5, electrolysis time of 75 minutes and 15 mm of inter-electrode distance. A comparison of colour removal between single EC and EC-Zeolite showed the same degradation performance. The interaction of hydrogen ion (H+) with aluminium hydroxide ion (Al (OH)3) produces during EC stabilises small particles forming larger sludge that reduces colour concentration. The removal of NH3-N increased from 50.0% to 93% when EC was integrated with clinoptilolite zeolite adsorption. In conclusion, the results show that both processes can potentially remove colour while the integrated process effectively removes NH3-N from landfill leachate. The proposed treatment helps optimise process performance while minimising the operational cost of the treatment. Thus, the proposed integrated EC – zeolite adsorption processes can be an alternative to landfill leachate treatment which aligns with the 12thMalaysia Plan to reduce pollution and carbon emissions to become a carbon neutral nation as early as 2050.

Deep learning assisted anode porous transport layer inverse design for proton exchange membrane water electrolysis

Proton exchange membrane water electrolysis cell (PEMEC) offers a clean and promising way for hydrogen production. The spatial internal current density and temperature distribution uniformity significantly determines its reliability and durability, as well as the hydrogen production performance. Here, a non-isothermal 3D computational fluid dynamics (CFD) model for PEMEC with parallel flow fields is employed to investigate the impacts of the heterogeneous porosity distribution within the anode porous transport layer (APTL) on the internal current density and temperature distribution uniformity and energy conversion performance. 800 heterogeneous APTL porosity distributions are applied for CFD calculation, providing dataset for deep learning. The deep operator network (DeepONet) is employed to mapping the heterogeneous APTL porosity distribution to the real physical fields such as temperature, oxygen molar fraction and current density distribution fields. Full-connected neural network is employed to construct the relationship between the heterogeneous APTL porosity distribution to the performance metrics. The gradient descent algorithm is applied to obtain APTL porosity distributions corresponding to the optimal internal current density and temperature distribution uniformity, respectively. Compared with the uniform porosity distribution, the current density and temperature uniformity are improved by 45.544 % and 26.680 %, respectively, at an average APTL porosity of 0.5.

Electronic band structure and optical properties of BGaAsBi/GaAs using 16 band kp Hamiltonian

The numerical simulations of optical and electronic properties of BGaAsBi/GaAs quantum wells (QWs) are obtained by diagonalizing the 16-band kp Hamiltonian with distinct boron and bismuth compositions that exhibit multifaceted potential in 1.3–1.5 μm. It has been observed that under strain-relaxed conditions for a doping concentration of 12.5 % (B, Bi), the anticipated values of spin-orbit (SO) coupling energy (ΔSO) and the bandgap (Eg) are 302 meV and 0.952 eV, respectively. Additionally, strain interaction on band structure decreases the band gap from (Eg = 0.92eV–0.85eV), increasing dopant concentration from 8 % to 12.5 %. The consequence of incorporating both Bi and B impurity is a reduction in electron effective mass of BGaAsBi by ∼1.3 times concerning the host GaAs, enhancing the optical properties of BGaAsBi/GaAs quantum-confined heterostructures. Moreover, an increase in well-width introduced a red shift and reduced the peak amplitude of the gain spectra. In addition, for solar cell application, the onset of the fundamental absorption edge is depicted at an energy of about 0.96 eV. For laser applications, the optimum threshold current density and quality factor of BGaAsBi/GaAs quantum well achieved at room temperature are 1089 A/cm2 and 3653, respectively, at well width (w = 2.0 nm), cavity length (L = 0.5 mm), and average thickness of the active region (d = 45 nm). The variation in power density is studied with injected current density, while the quality factor is calculated with well width. The outcomes could be beneficial for future use in optical devices.

Performance analysis of PEMFC-assisted renewable energy source heat pumps as a novel active system for plus energy buildings

The adoption of plus energy buildings (PEBs) has been considered extensively in various nations for carbon neutralization. However, studies on suitable active systems that can efficiently supply heating, cooling, and electrical energy to PEBs are lacking. This study proposes PEMFC-assisted renewable energy source heat pumps (PEMFC-RSHPs) as active systems for plus energy buildings. In the steady-state simulations using TRNSYS, the waste-heat recovery effect was investigated at various current densities and PEMFC temperatures. In the transient simulations, the seasonal operating characteristics, energy, economic, and environmental performances of PEMFC-RSHPs using air, raw-water, and ground energy sources were analyzed. During the heating season, the maximum primary energy efficiency (PEF) of a PEMFC-assisted ground source heat pump (GSHP) was approximately 0.252 at an optimal current density of 0.8 A cm−2. However, during the cooling season, the PEMFC-assisted raw-water source heat pump (RWSHP) showed the highest PEF of 0.407 at an optimal current density of 0.7 A cm−2. In addition, the CO2 emissions of the PEMFC-GSHP using green hydrogen were 54.3% lower than those using gray hydrogen, although the economic feasibility was still challenging. In conclusion, the PEMFC-GSHP using green hydrogen is the most feasible active system for PEBs.

Direct electron transfer mediated electrochemical activation of persulfates by reticulated vitreous carbon (RVC) cathode

The electrochemical activation of peroxymonosulfate (PMS) and peroxydisulfate (PDS) for pollutant degradation has gained increasing attention. In this work, reticulated vitreous carbon (RVC) electrodes were prepared at a low cost and investigated for the cathodic activation of PMS/PDS for Acid Orange 7 degradation. The RVC was characterized by SEM, TGA, XRD, Raman spectroscopy, XPS, EIS, and compression test. The superior activity outperformed previous reports in terms of low current density operation (1–10 mA/cm2), high degradation rates (0.13–0.49 min−1), low energy consumption (0.03–0.23 kWh/m3/order) without involvement of catalysts. The process was optimized for current density, PMS dosage, pollutant concentration, pH, water matrix, and supporting electrolyte. Under the optimal current density (3 mA/cm2), the addition of 0.5 mM of PMS boosted the degradation rate by 9.6 times to 0.4470 min−1 and reduced the electrical energy consumption by 90.1 % to 0.0243 kWh/m3/order in 50 mM of Na2SO4. Moreover, up to 117 mg/L of H2O2 was produced in 1 hour by the reduction of oxygen, with current efficiencies between 78–24 %. The process showed little deterioration in 10 cycles, worked for a variety of pollutants, and was not affected by the water matrix. The H-cell experiments confirmed that 90 % degradation took place on the cathode. Scavenging experiments and electrochemical tests suggested that the transitional state of PMS* and O2•− mediated the direct electron transfer mechanism for AO7 degradation. Eighteen degradation products were identified by HPLC-MS and categorized into 4 degradation pathways. Finally, their toxicity was assessed by the ECOSAR programme.

Separation and conversion of CO2 reduction products into high-concentration formic acid using bipolar membrane electrodialysis

Electrochemical CO2 reduction to value-added chemicals such as formate represents a crucial pathway in advancing carbon-neutral fuel production. However, the separation of formate from KHCO3 electrolyte solutions and its conversion to formic acid remain cost intensive steps in this process. This study demonstrated the use of bipolar membrane electrodialysis (BMED) to efficiently convert and concentrate formic acid directly from a cathodic solution for CO2 electroreduction. The migration of formate ions during BMED was optimized under different cell configurations and current densities. Mathematical modelling was developed to predict the concentration evolution curves of formic acid production. The results showed that formic acid diffusion through an anion-exchange membrane was more pronounced than that a bipolar membrane; the former diffusion was a key factor that limited the formic acid concentration and reduced the current efficiency. A formic acid concentration of 3.49 mol/L was obtained at an optimum current density of 40 mA/cm2 and a salt-to-acid compartment volume ratio of 25:1. Thus, BMED has emerged as a viable and effective technique for isolating high-purity formic acid from a cathodic solution for CO2 electroreduction.

Optimal current density for cathodic CeCC deposition on anodized AA2024-T3 aircraft alloy

Optimal current density for cathodic CeCC deposition on anodized AA2024-T3 aircraft alloy

Preparation of N, S doped Co-Fe/C catalyst derived from ZIF-67/ionic liquid and its catalytic activity for oxygen reduction reaction in alkaline electrolyte

ZIF-67(CoFe) was synthesized using the solvothermal method, and the precursor of ZIF-67(CoFe)/xC-yIL was obtained by grinding the mixture of ZIF-67(CoFe), [BMIM][NTf2] ionic liquid (IL), and carbon black. A series of ZIF-67(CoFe)/xC-yIL-T catalysts were prepared by calcining the precursor at different temperatures. The structure of the catalysts was examined using XRD, TEM, BET and XPS analysis. The results show that the high-temperature treatment of the precursor contributes to the formation of the structure of the N, S-co-doped carbon-coated nanoparticles. The introduction of ionic liquid increases the specific surface area of the catalysts and exposes more active sites. At the same time, as a sulfur source, ionic liquid forms a C-S bond, which is conducive to improving ORR activity. The optimal ORR half-wave potential and limited current density of ZIF-67(CoFe)/1.5 C-45IL-600 are 0.87 V vs. RHE and 4.64 mA cm-2, respectively, in 0.1 mol L−1 KOH.

Chrysanthemum‐Flowers‐Like Bimetal Oxide Based Electrocatalyst for Methanol Oxidation Reaction

Transition metal oxides have garnered attention for the methanol electro‐oxidation reaction owing to their easy availability, high catalytic applicability, and multiple oxidation capabilities. Bimetal‐based catalysts further enhance the performance of the methanol oxidation reaction. In this context, a chrysanthemum‐flower‐like MoO2/WO3 is synthesized through a solvothermal and annealing strategy. The morphology attests to the rough surface and pores in the catalyst, augmenting its surface area for reactions and enhancing catalytic applicability. Electrochemical oxidation of methanol yields an optimal current density of 0.99 mA cm−2 and 2.07 mA mg−1 at a potential of 0.57 V versus Ag/AgCl. The catalyst exhibits a remarkably low Tafel slope of 37.45 mV dec−1, affirming its rapid reaction kinetics. Electrochemical impedance spectroscopy (EIS) reveals an equivalent electronic circuit of R(Q(R(QR)Q(RW))), confirming low charge transfer resistance (Rct) and diffusion‐controlled kinetics attributable to the pores in the sample. The sample also demonstrates an electrochemically active surface area (ECSA) value equal to 0.122 mF cm−2 and long‐term stability over continuous 5000 s, exhibiting no change and high resistance to CO poisoning. All these characterizations and obtained results collectively affirm that the chrysanthemum‐flower‐like MoO2/WO3 serves as a highly suitable electrocatalyst for the electrochemical oxidation of methanol.