Electrolysis Cell Research Articles

Enhanced overall water splitting by morphology and electronic structure engineering on pristine ultrathin metal-organic frameworks

Metal-organic frameworks (MOFs) have caused extensive attention attributed to their widespread applications including electrocatalysis by virtue of their distinctive structural characteristics. However, the direct application of pristine MOFs as bifunctional electrocatalysts is quite challenging due to their insufficient active sites and poor electrical conductivity. In this research, the ultrathin tri-metal (Fe, Co, and V) doped FeCoV-NiMOF nanosheet arrays were prepared through a facile hydrothermal method. Benefiting from the distinctive ultrathin (1.5 nm) nanosheet arrays and electronic structure reconfiguration induced by heteroatom doping, the prepared FeCoV-NiMOF displays the low overpotentials of 238, 309, and 408 mV for oxygen evolution reaction (OER) and 144, 255, and 349 mV for hydrogen evolution reaction (HER) at the current densities of 10, 100, and 1000 mA cm−2, respectively, outperforming the vast majority of previously reported bifunctional pristine MOFs. The electrolytic cell utilizing FeCoV-NiMOF as both cathode and anode requires just 1.61 V to attain 10 mA cm−2 and displays superior stability of 100 h at 100 mA cm−2. In the anion exchange membrane electrolyzer, as-prepared FeCoV-NiMOF needs a low cell voltage of 2.16 V at 500 mA cm−2 for effective overall water splitting, demonstrating its substantial potential as bifunctional electrodes for H2 production. The viable and efficient strategy in this study exhibits great prospects to enrich the exploration of bifunctional MOF-based electrocatalysts with superior performance for renewable energy conversion.

Vanadium-Doped Ni3S2: Morphological Evolution for Enhanced Industrial-Scale Water and Urea Electrolysis.

We report the V-Ni3S2 self-supported catalytic network with optimized morphology grown directly on nickel foam (NF) by the one-step hydrothermal technique for water and urea electrolysis at industrial scale hydrogen generation. The morphology of Ni3S2 was modulated by doping of different concentrations of vanadium from granules to cross-linked wires to hierarchal nanosheets arrays, which is beneficial in electrochemical charge and mass transport, and generates more exposed active sites. The V-Ni3S2 catalyst requires the overpotential of 147 mV for hydrogen evolution reaction (HER). The OER and UOR half-cell reaction on V-Ni3S2 catalyst requires potential 1.57 V and 1.39 V (vs RHE), respectively to generate current 100 mA/cm2. The water electrolysis cell developed by V-Ni3S2 as both anode and cathode generates 100 mA/cm2 at cell voltage of 1.88 V in laboratory condition (1M KOH, 25°C) and 1.61 V at industrial condition (5M KOH, 80°C) and also shows considerable stability for 82hr at current 300 mA/cm2. The urea electrolysis cell with 1M KOH and 0.33 M urea generates 100 mA/cm2 at a cell voltage of 1.73 V, which is 150 mV less than that required for water electrolysis and demonstrate stability for 85hr at a current of 100 mA/cm2.

Long-term electrochemical characterization of novel Sr2FeMo0.65Ni0.35O6−δ fuel electrode for high-temperature steam electrolysis in solid oxide cells

The present study focuses on the highly catalytic double-perovskite Sr2FeMo0.65Ni0.35O6−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.

Is it stable for the asymmetric pressure operation of PEM water Electrolyzer?

Benefiting from the high selectivity of solid polymer membrane in transporting protons, proton exchange membrane water electrolyzer (PEMWE) have the unique capability of safely operating under asymmetric pressure between the cathode and anode (typically with the cathode under elevated pressure and the anode at ambient pressure). This capability is crucial for high-pressure hydrogen storage and transportation, as well as for rapid response to fluctuating renewable electricity. Although increased cathode pressure significantly simplifies system integration and reduce capital cost, the stability under asymmetric pressure operation has not been well studied and reported. In this work, durability tests under different pressure differences were carried out, and it was found that when the pressure difference between cathode and anode increases from zero to 3.0 MPa, the voltage decay rate increased over 15 times. The underlying reason is that the asymmetric pressure imposes additional mechanical stress on the anode catalyst layer from cathodic side, leading to increase of mass transfer resistance and irreversible structural damage, resulting in performance degradation. In view of this fact, the internal structure of the electrolyzer cell was optimized, and the uneven stress distribution and stress concentration was greatly reduced, thus mitigating performance degradation. This indicates that the stability of PEMWE is significantly affected by asymmetric pressure, additional measures need to be taken to address potential issues of catalyst layer structural damage arising from stress.

Generating Hydrogen Gas with a Polyvinyl Alcohol Membrane Dry Cell Electrolyzer Using KOH Electrolyte

Global environmental concerns requiring excellent air quality have prompted the development of a variety of eco-friendly energy sources. Hydrogen gas is an environmentally friendly option that may be created using an electrolysis device that converts water into hydrogen (H2) and oxygen (O2). In this study, a dry cell electrolyzer with a polyvinyl alcohol (PVA) membrane was used as a separator between two stainless steel 316 electrodes to generate a high hydrogen yield. The hydrogen gas production from the dry cell electrolyzer was determined using gas chromatography. The results showed that using a KOH electrolyte and a PVA membrane considerably enhanced the hydrogen gas composition. Hydrogen gas compositions after electrolysis using a dry cell electrolyzer without a PVA membrane and KOH electrolyte concentrations of 0 M, 0.04 M, 0.07 M, and 0.11 M being 13.70%, 25.10%, 32.50%, and 15.60%, respectively. With a PVA membrane, the hydrogen compositions were 71.50%, 89.10%, 80.50%, and 84.60%, respectively. The results of these experiments show that the most hydrogen gas was produced utilizing a dry cell electrolyzer with a PVA membrane and a 0.04 M KOH electrolyte concentration. When a PVA membrane and a KOH electrolyte are utilized in electrolysis, the hydrogen gas composition improves significantly compared to when either is utilized.

Combined water electrolysis and 2D hydron separator for enhanced hydrogen isotope separation

This research presents the fabrication and analysis of a graphene/Nafion composite membrane designed to enhance the hydrogen separation performance of a water electrolyzer by leveraging the isotope effect in hydron transport through monolayer graphene, serving as a 2D hydron separator. The composite membrane exhibits lower proton conductivity than a Nafion membrane, leading to a 12 % decrease in water electrolysis cell efficiency at 75 °C. However, the incorporation of monolayer graphene substantially enhances the hardness of the membrane by a factor of 1.38, as measured by nanoindentation. The addition of monolayer graphene also increases the activation energy required for through-plane conduction of H+ and D+, with the graphene itself showing a twofold higher conductivity for H+ over D+. In electrolysis cells containing the composite membrane, the H/D and H/T separation factors improved by approximately 1.4 and 2 times, respectively, compared with those of a Nafion membrane, with a maximum H/T separation factor of ∼ 15 at 15 °C. Although increases in temperature reduce the separation factor, the operation time and the concentration of heavier isotopes in the feed water were found to minimally affect the separation efficiency.

Surface active sites and interphase engineering into metal oxide hydrates enabled by ions substitution for efficient water splitting

The expanding requirement of energy-effective and cost-efficient water electrolysis has prompted studies of earth-abundant metal-based electrocatalysts. In this study, we study the typical substitution strategies of cation (Pt) or anion (Se) for modifying surface active sites or interphase engineering to tune electronic structure of bimetallic nickel molybdenum oxide hydrates (NiMoO4·xH2O), thus effectively improving catalytic properties toward hydrogen evolution reaction (HER) or oxygen evolution reaction (OER). Result of the cation substitution achieves PtSA–NiMoO4·xH2O catalyst with abundant doped Pt single atoms on surface, which promotes high HER activity with a small overpotential of 73 mV at a current yield of 10 mA cm−2 in alkaline medium. Meanwhile, Se–NiMoO4·xH2O catalyst, an outcome of the anion substitution approach, has unique interfaces of NiSe-NiMoO4 heterostructure and thus exhibits a desired overpotential of only 297 mV for OER. The combination of PtSA–NiMoO4·xH2O(–)//Se–NiMoO4·xH2O(+) couple results in a two-electrode electrolyzer cell, which requires a small cell voltage of 1.48, 1.54 and 1.59 V to deliver a response of 10 mA·cm−2 at 75, 50 and 25 °C, respectively, along with negligible performance decay during 50 h operation. These results highlight the potential of our catalyst engineering strategies to achieve high-performance green hydrogen production.

Hydrogen production through polyoxometalate catalysed electrolysis from biomass components and food waste

Electrolysis from biomass is a promising process for hydrogen generation from biomass and biowaste that is still unexplored. The paper used lignocellulosic biomass components and food waste (banana and cucumber peels) as feedstocks to explore hydrogen generation through an H-type proton exchange membrane electrolytic cell. Polyoxometalates (PMo12) were employed as a catalyst and charge carrier during the pre-treatment stage in the biomass degradation process. Electrochemical characterisations were conducted in a potential range of 0–1.20 V to analyse the electrochemical reaction behaviour at the anode. To assess the impact of temperature on the hydrogen yield rates, the electrolysis was conducted at both room temperature (19 °C) and a higher temperature (80 °C). Results show that the maximum hydrogen produced in the first hour was 7.8 mL per gram of biomass. With an electrical potential of 1.20 V and a temperature of 80 °C, the hydrogen yield rate of glucose was three times higher than that of the individual biomass components, i.e., cellulose, lignin, hemicellulose, and starch. The volume of hydrogen yielded from banana peel and cucumber was 49.2 mL and 39.6 mL, respectively. The overall conversion efficiency was calculated as the weight percentage ratio of the hydrogen contained in cucumber and banana peels and the hydrogen collected was 10 % and 17 %, respectively, suggesting the need to identify solutions to extract the hydrogen content from biomass material further.

Bionic Janus microfluidic hydrogen production with high gas–liquid separation efficiency

Water electrolysis offers the advantages of emission-free and highly efficient energy conversion in terms of sustainable energy development and environmental pollution. However, water electrolysis is strongly affected by the detachment of bubbles from the electrodes commonly enabled by buoyancy, thereby reducing the performance of the electrolytic cells in harsh environments like in space. Herein, a bionic Janus microchannels with active gas–liquid separation for water electrolysis is proposed. There is a Janus membrane with superaerophilic top surface and inner micropores over the microchannels, and such a unique type of microchannels can capture and unidirectionally manipulate the hydrogen (H2) bubbles generated on the surface of the electrode during the water electrolysis reaction at high speed with long-term stability. It is worth noting that the gas–liquid separation through the Janus membrane does not hinder the flow of electrolyte in the microchannel due to its hydrophilic inside surfaces, which can maintain the great stability of the electrolysis. Moreover, mimicked leaves and trees for water catalysis are further demonstrated with ultrahigh electrolysis efficiency based on the active detachment of H2 bubbles enabled by Janus micropores. The present bionic Janus microchannels for high-efficient water electrolysis to produce H2 is intended to provide a new power supply solution for human space living and exploration.

An Efficient Trifunctional Spinel-Based Electrode for Oxygen Reduction/Evolution Reactions and Nonoxidative Ethane Dehydrogenation on Protonic Ceramic Electrochemical Cells.

Protonic ceramic electrochemical cells (PCECs) have received considerable attention as they can directly generate electricity and/or produce chemicals. Development of the electrodes with the trifunctionalities of oxygen reduction/evolution and nonoxidative ethane dehydrogenation is yet challenging. Here these findings are reported in the design of trifunctional electrodes for PCECs with a detailed composition of Mn0.9Cs0.1Co2O4-δ (MCCO) and Co3O4 (CO) (MCCO-CO, 8:2 mass ratio). At 600°C, the MCCO-CO electrode exhibits a low area-specific resistance of 0.382 Ω cm2 and reasonable stability for ≈105h with no obvious degradation. The single cell with the MCCO-CO electrode shows an encouraging peak power density of 1.73W cm-2 in the fuel cell (FC) mode and a current density of -3.93 A cm-2 at 1.3V in the electrolysis cell (EC) mode at 700°C. Moreover, the MCCO-CO cell displays promising operational stability in FC mode (223h), EC mode (209h), and reversible cycling stability (52 cycles, 208h) at 650°C. The MCCO-CO single cell shows an encouraging ethaneconversion to ethylene (with a conversion of 40.3% and selectivity of 94%) and excellent H2 production rates of 4.65mL min-1 cm-2 at 1.5V and 700°C, respectively, with reasonable Faradaic efficiencies.

Effects of Sintering Aids and Thickness on Densification and Properties of Magnesia-Aluminum Spinel Transparent Ceramics in the Aluminum Electrolysis Cells

Effects of Sintering Aids and Thickness on Densification and Properties of Magnesia-Aluminum Spinel Transparent Ceramics in the Aluminum Electrolysis Cells

Parametric study of PEM water electrolyzer performance

AbstractGreen hydrogen can contribute significantly to combating climate change by helping to establish an energy economy that is both sustainable and carbon-free. One pathway to obtaining green hydrogen is by water electrolysis powered by renewable energy. Proton exchange membrane water electrolysis (PEMWE) is a promising option owing to its high current density at high efficiency. Here, we report on experimental results from a parametric investigation of PEMWE. We have examined the effect of water flow rate at 80 °C using a 5 cm2 PEM electrolyzer cell hardware and lab-fabricated membrane electrode assemblies. The results showed that a water flow rate of 0.08 ml cm−2 min−1 was sufficient to meet the water consumption by electrochemical reactions at the anode as well as water depletion by diffusion and electroosmotic drag. We then employed this optimal flow rate to examine the effect of various operating parameters on PEMWE performance and efficiency such as operating temperature, membrane thickness, flow field channel configuration, and porous transport layers as a function of the applied voltage. The results provide useful insights into the operating conditions for optimal PEMWE performance. Graphical abstract

Sn doped cobalt-based phosphide as bifunctional catalyst for ethanol oxidation reaction and hydrogen evolution reaction

The development of non-precious metal bifunctional electrocatalysts is of practical significance to solve resource shortage and energy crisis. In this study, to accelerate mass/electron transfer and maximize the area of exposed active sites, a coral-like Sn–Co–P/NF bi-functional electrocatalyst was synthesized by electrodeposition for total hydrolysis. Ethanol oxidation reaction (EOR) was used to replace oxygen evolution reaction (OER) with hydrogen evolution reaction (HER) to further improve the water electrolysis rate. The catalyst showed great electrochemical activity and stability in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under alkaline conditions. At a current density of 10 mA cm−2, the required overpotential for HER is only 59 mV (vs. RHE) and 304 mV (vs. RHE) for OER, and the corresponding Tafel slopes are 42 mV·dec−1 and 67 mV·dec−1, respectively. When EOR was substituted for anodic oxygen evolution, the overpotential could be reduced by 240 mV. In addition, when Sn–Co–P/NF is used as a water-ethanol electrolytic cell assembled with anode and cathode, the current density of 10 mA cm−2 can be reached with only 1.49 V operating voltage, which is 130 mV lower than that of hydrolysis alone, and it also shows good durability in the test of 28 h. Therefore, the experimental results show that it is feasible to use EOR instead of OER to coupling with HER, the catalyst has broad application prospects in industrial electrolysis.

Optimal operation of solid-oxide electrolysis cells considering long-term chemical degradation

Optimizing the performance of solid oxide electrolysis cells (SOECs) for long-term hydrogen (H2) production at high temperatures is crucial, as prolonged operation leads to efficiency losses and shorter cell lifespans due to chemical degradation. In this work, we adopt a quasi-steady state approach for dynamic optimization over extended operational periods to address the disparity in timescales between cell operation and degradation. Integrating a 2-D non-isothermal SOEC model with balance-of-plant (BOP) equipment, we explore three optimization objectives: minimizing terminal degradation, maximizing integral efficiency, and minimizing the levelized cost of H2 (LCOH). Our dynamic optimization algorithm reduces LCOH by 9.5% and 16% compared to strategies focusing solely on terminal degradation and integral efficiency, respectively. For electricity prices of 0.03 $/kWh and 0.3 $/kWh, optimal replacement schedules range from 5 to 2 years, depending on the operational mode. Furthermore, a flexible operational mode yields additional improvements in LCOH over traditional galvanostatic and potentiostatic modes.

High-Efficiency Hydrogen Recovery from Corn Straw Hydrolysate Using Functional Bacteria and Negative Pressure with Microbial Electrolysis Cells

This study attempts to overcome the challenges associated with the degradation of complex organic substances like corn straw hydrolysate in hydrogen recovery by strategically enriching functional microbial communities in single-chamber cubic microbial electrolysis cells (MECs). We applied negative pressure, using acetate or xylose as electron donors, to mitigate the hydrogen sink issues caused by methanogens. This innovative method significantly enhanced MEC performance. MECs enriched with xylose demonstrated superior performance, achieving a hydrogen production rate 3.5 times higher than that achieved by those enriched with acetate. Under negative pressure, hydrogen production in N-XyHy10 reached 0.912 ± 0.08 LH2/L MEC/D, which was 6.7 times higher than in the passive-pressure MECs (XyHy10). This advancement also resulted in substantial increases in current density (73%), energy efficiency (800%), and overall energy efficiency (540%) compared with MECs operated under passive pressure with 10% hydrolysate feed. The enrichment of polysaccharide-degrading bacteria such as Citrobacter and Pseudomonas under negative pressure underscores the potential for their industrial application in harnessing complex organic substrates for bioenergy production in single-chamber MECs. This is a promising approach to scaling up bioenergy recovery processes. The findings of this research study contribute significantly to the field by demonstrating the efficacy of negative pressure in enhancing microbial activity and energy recovery, thereby offering a promising strategy for improving bioenergy production efficiency in industries.

Efficient technology for food waste valorization: an integrated anaerobic digestion—microbial electrolysis cell for biomethane production

Efficient technology for food waste valorization: an integrated anaerobic digestion—microbial electrolysis cell for biomethane production

Thermodynamic performances of a power-to-X system based on solar concentrating photovoltaic/thermal hydrogen production

100% renewable power-to-X (fuel, power, and heat products) systems have great application potential for the achievement goal of carbon neutrality. However, the extensive chain of the power-to-X system could result in low energy utilization efficiency. A novel composite-parabolic-concentrating photovoltaic/thermal-collector-based power-to-X system utilizing 100% solar energy is proposed, which integrates proton exchange membrane electrolysis cells and proton exchange membrane fuel cells to provide heat, electricity, and hydrogen. Thermodynamic models for each subsystem are established, and energy and exergy efficiencies are assessed in the thermodynamic laws. Three operation modes are analyzed to adapt to the variations of solar radiation and a residential building is used as an application scenario to evaluate its thermodynamic and economic performances in dynamic variations of solar radiations and energy demands. The effects of key operating parameters, such as solar radiation intensity, photovoltaic coverage ratio, current density, and operating temperature, on the performances are investigated. The maximum exergy destruction of the concentrator photovoltaic/thermal collector is 93.20% at the rated operating conditions, and the system exergy and energy efficiencies are 9.11% and 48.97%, respectively. The economic results demonstrate that the levelized costs of solar power, hydrogen, and fuel cell power are 0.2936 $/kWh, 21.70 $/kg, and 2.1520 $/kWh, respectively.

Cellulosic ethanol stillage for methane production by integrating single-chamber anaerobic digestion and microbial electrolysis cell system

Anaerobic digestion provides a solution to the inefficient use of carbon resources caused by improper disposal of corn stover-based ethanol stillage (CES). In this regard, we developed a single-chamber anaerobic digestion integrated microbial electrolysis cells system (AD-MEC) to convert CES into biogas while simultaneously upgrading biogas in-situ by employing voltages ranging from 0 to 2.5 V. Our results demonstrated that applying 1.0 V increased the CH4 yield by 55 % and upgraded the CH4 content in-situ to 82 %. This voltage also promoted the well-formed biofilm on the electrodes, resulting in a 20-fold increase in current. However, inhibition was observed at high voltages (1.5–2.5 V), suppressing syntrophic organic acid-oxidizing bacteria (SOB). The dissociation between SOB and methanogens led to accumulation of propionic and butyric acid, which, in turn, inhibited methanogens. The degradation of CES was accelerated by unclassified_o_norank_c_Desulfuromonadia on the anode, likely leading to an increase in mixotrophic methanogenesis due to the synergistic interaction among Aminobacterium, Sedimentibacter, and Methanosarcina. Furthermore, the enrichment of electroactive bacteria (EB) such as Enterococcus and Desulfomicrobium likely facilitates direct interspecies electron transfer to Methanobacterium, thereby promoting the conversion of CO2 to CH4 through hydrogenotrophic methanogenesis. Rather than initially stimulating the EB in the bulk solution to accelerate the start-up process of AD, our study revealed that applying mild voltage up to 1.0 V tended to mitigate the negative impact on the original microorganisms, as it gradually enriched EB on the electrode, thereby enhancing biogas production.

Design, fabrication, and performance assessment for green hydrogen production unit

Creating and building an integrated system that consists of a storage tank, an electrolysis cell with many electrolyzer types, and a green hydrogen generator that produces clean, sustainable gas using solar photovoltaic (PV) energy and renewable energy sources. Three different electrolyzer modules with six, eleven, and twenty-one plates each were created locally and meant to be utilized in the production of green hydrogen. The hydrogen storage system's design was also created. It is clear that the maximum value of hydrogen production is recorded in the following ordered: KOH (5.5 L/min) > NaOH (1.2 L/min) > NaCl (0.7 L/min) > MgSO4 (0.4 L/min). Also, sea water was used as electrolyte solution with different dilution 5, 10, 15, and 20% using a natural sea water sample collected from the Mediterranean Sea. It is found that 15% sea water dilution reaches the maximum value of H2 production (3.4 L/min). Using distilled water and tap water, respectively, the volume of generated H2 gas reached its maximum value of 8 L/min and 6.5 L/min at 0.4 mols of KOH. It was observed that with increased time durations (0–90 min), enhance the rate of hydrogen production to be reaches 8.2 and 11.5 L/min when using 0.05 and 0.1 mols KOH, respectively. This approach reduces environmental effect and operational costs, providing a sustainable solution to the water and energy problems.

Enhanced water and urea electrolysis at industrial scale current density using self-supported VxNi1-xO trifunctional catalysts

An advance of highly efficient nanostructured electrocatalysts based on non-noble metals for water electrolysis and urea oxidation reaction (UOR) are of great significance for urea-enriched wastewater remediation and producing hydrogen. Herein, we report VxNi1-xO catalysts supported on three-dimensional Ni-foam scaffold for catalytic water and urea electrolysis. VxNi1-xO catalysts show rapid water and urea electrolysis due to enhanced electrochemical surface area (ECSA). Most important of all, the urea oxidation reaction has a lower potential of 1.418V vs RHE as compared to oxygen evolution reaction (1.684 V vs RHE) system to generate 100 mA/cm2. Additionally, a two-electrode cell for bi-functional water electrolysis generates 100 mA/cm2 at a potential of 2.10 V at 20 °C and just 1.86 V at 60 °C temperature due to regulated the adsorption/desorption of intermediates species, enhanced charge and mass transport, and easier desorption of oxygen molecules from the anode. The stability of VxNi1-xO catalyst was measured at 1000 mA/cm2 current density for up to 17 h.