Bahman Amini Horri

Manganese metal can serve as a secondary energy carrier for hydrogen, offering a cost-effective solution for energy storage and transport. This process can be realised through the hybrid manganese cycle. In this study, a large-sized electrolyser was specifically designed to perform the complete circulation of water splitting. The results indicate that the designed electrolyser significantly reduces the mass transfer impedance. However, the zero-gap structure on the anode side proves unsuitable for this system, as it leads to the occurrence of the manganese oxidation reaction (MOR), even when potassium sulphate is employed as a reaction inhibitor. In addition to its role in inhibiting manganese oxidation, the anodic addition of potassium sulphate was revealed to reduce the onset cell voltage of the manganese electrodeposition reaction (MEDR) and the current density. The optimal concentration of potassium sulphate in the anolyte was determined to be 0.2 mol/L. Furthermore, an anode-PEM distance of 2.5 mm was found to be most appropriate, as it ensures a sufficient local proton environment to completely inhibit manganese oxidation while also improving the current density. In addition, electrolyte circulation was optimised, with the best performance observed at a peristaltic pump speed of 100 rpm. Based on the optimised electrolyser, production tests were conducted. It was found that electrolysis duration influences both the manganese and hydrogen current efficiencies, thus affecting the overall energy conversion efficiency (OECE). The most favourable electrolysis was achieved at a duration of 600 s, resulting in improvements in the OECE, current density, and productivity by 3.47 %, 179.84 %, and 115.22 %, respectively, compared to the H-cell.

This study systematically investigates the thermal decomposition, densification behaviour, microstructural evolution , electronic structure, ionic conductivity, and electrochemical performance of Bi and Cu co-doped GDC (2B1C) powders. Thermal expansion and sintering analysis reveal that the 2B1C powders exhibit excellent low-temperature sinterability, achieving near-full densification with a relative density of 98.6 % at 750 °C, and further reaching 98.7 % at 850 °C, which is significantly lower than the sintering temperature of conventional GDC. XRD and SEM results confirm high purity and well-formed crystalline structures with advanced densification. XPS and Raman analyses reveal that doping modulates the defect chemistry and enhances oxygen vacancy concentration. Impedance spectroscopy shows that 2B1C-2 achieves the highest ionic conductivity of 2.12× 10^-2 S·cm −1 at 750 °C. Moreover, in a practical SOC cell configuration, the YSZ-supported cell with a 2B1C barrier layer demonstrates capable electrochemical performance, achieving a maximum power density of 235.1 mW/cm 2 at 850 °C. Overall, Bi and Cu co-doping significantly lowers the sintering temperature and enhances ionic conductivity, making 2B1C a promising electrolyte candidate for metal-supported solid oxide cells (SOCs) at reduced processing temperatures.

Solid oxide electrolysis cells (SOECs) are among the most efficient energy‐conversion devices for power‐to‐X applications in green energy technologies. Here, we report a high‐level (5 mol%) Li‐ and Co‐dual‐doped gadolinium‐doped ceria (GDC) electrolyte synthesized under an inert atmosphere, suitable for fabricating SOECs using conventional ferritic steel supports. The doped GDC exhibits uniform dopant incorporation and a single‐phase cubic fluorite structure, achieving 98.18% relative density at 950 °C. Dilatometry and microstructural analyses reveal that Li–Co codoping significantly reduces sintering temperature and improves grain connectivity. Time‐of‐flight secondary ion mass spectrometry shows a Li,Co‐rich surface layer whose thickness depends on sintering conditions, while Raman spectroscopy confirms the presence of a LiCoO 2 phase and temperature‐dependent oxygen‐vacancy concentration. Electrochemical impedance spectroscopy demonstrates enhanced ionic conductivity, particularly for the sample sintered at 950 °C (denoted 5LC‐4), which achieves increases of 269.5% at 450 °C and 138.85% at 750 °C compared with commercial GDC. The ionic conductivity reaches 2.17 × 10 −2 S cm −1 with an activation energy of 0.32 eV. A symmetric five‐layer SOEC integrating 5LC‐GDC exhibits superior electrochemical performance to yttria‐stabilized zirconia (YSZ) support, achieving a peak power density of 267.5 mW cm −2 at 850 °C.

This study investigates the impact of vibration frequency on the performance of a 10-cell open-cathode direct methanol fuel cell (OC-DMFC) stack. Experiments were conducted using three different vibration frequencies (15, 30, and 60 Hz) and compared against a baseline condition without vibration. Performance was evaluated under varying methanol–water fuel flow rates (1, 5, 25, and 50 mL·min−1) while maintaining constant operating conditions: methanol temperature at 70 °C, methanol concentration at 1 M, and cathode air flow velocity at 4.8 m·s−1. The optimal performance was observed at a fuel flow rate of 5 mL·min−1, where the maximum power density reached 26.05 mW·cm−2 under 15 Hz vibration—representing a 14% increase compared to the non-vibrated condition. These findings demonstrate that low-frequency vibration can enhance fuel cell performance by improving mass transport characteristics.

This study investigates the optimisation of the electrochemical performance of a novel Mn/MnSO₄ redox cycle using monovalent cations, including Li + , Na + , and K + , to enhance hydrogen generation. The reaction mechanism of cations in the simultaneous hydrogen evolution reaction (HER) and manganese electrodeposition reaction (MEDR) was confirmed through a systematic analysis of the co-evolution stages to maximise the cell electro-chemical performance. The results indicated that the effects of cations primarily depend on the differences between the activation of ion pairing/bridging and the inactivation of surface blocking for the HER and MEDR, along with the influence of mass-to-charge ratio, ion size, conductivity, ion distribution, and concentration polar-isation. A high concentration of cations can efficiently boost the cell performance and current density due to the enhancement of HER, even though it simultaneously leads to the inhibition of MEDR, presenting high energy efficiency and productivity, but low manganese CE. Optimal performance was achieved by adding K + cations using 0.8 mol/L potassium sulphate (K 2 SO 4) solution to MnSO 4 , with a pH of 2.86, which resulted in 7.16 % improved current efficiency. In addition, it was found that potassium cations can make the electrodeposited manganese metal more easily detached from the electrode and cause a lower corrosion current density, which is in favour of production. The proposed system and approach offer the advantages of reducing specific energy consumption by 7.23 % compared to the conventional cells, providing new insights into the electrochemical behaviour of redox pairs mediated water splitting systems for the next generation of scalable, low-cost PEM electrolysis systems for sustainable hydrogen production.

Solid oxide electrolysers (SOE) are a promising type of technology of hydrogen production with the potential to be a part of the sustainable future of the energy sector. Advantageous efficiency of these devices is coming from the combined use of the heat and electrical energy. The current research proposes to improve the electrical efficiency of solid oxide electrolysers by fabricating a metasurface upon the standard porous anode layer of the electrolysis cell. The study considers the tubular cell design with the thick metallic support and several types of meta-elements, including squared shapes, lines parallel to the air flow and a net-structured surface. Computational fluid dynamics (CFD) analysis is performed for the 1/16 sector model of the tubular cell in parallel flow conditions to evaluate current density characteristics of the considered metasurfaces. As a result of this study, the net-structured metasurface is found to increase the current density by 8.5 %.
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•Tubular solid oxide electrolysis (SOE) cell investigated with the metallic support.•Introduced a metasurface-patterned anode structure for enhanced performance.•Simulations are performed for the 1/16th sector model of the short tubular cell.•Current density evaluated for four types of the porous anode metasurface.•Net-structure metasurface of the porous anode found to be the most efficient by 8.5 %.

This work pioneers an efficient and scalable fabrication approach of silver (Ag) current collector (CC) layer on a porous stainless steel (SS-316L) tubular substrate for solid oxide electrolysis cell (SOEC). An Ag layer was fabricated on porous SS support using the electrodeposition technique. The highest current density 283 mA/cm(2) was achieved with an optimised concentration of 0.1 M of AgNO3 solution containing 5.0 % HNO3 and an applied voltage of 2.0 V. It has been found that the strong acidic medium facilitates the migration of silver cations under controlled voltage towards the cathode. The structural properties were analysed by Raman spectroscopy and X-ray photoelectron spectroscopy to confirm the phase purity and structural properties of silver layer. The deposited Ag was a bright, uniform and well-adhered coating with an average coating thickness of 28 mu m in the sintered tube. An improved electrochemical performance was attributed to the Ag-coated sample (sigma = 1.24 x 10(-4) S.cm(-1)) measured by impedance spectroscopy. The cyclic voltammetry studies of Ag coating reveal pseudo-capacitive behaviour due to its relatively low storage capacity. Ag-coated SS stable cathodic polarisation behaviour at higher potential (>1.99 V) with relatively higher corrosion potential (E-corr = -0.05 V) signifies better corrosion resistant. AC impedance spectroscopy at 800 degrees C demonstrated that silver-coated SS current collector reduces area-specific resistance to 2.16 Omegacm(2) in complete SOECs (SS/NiO-YSZ/GDC/LSCF-YSZ). This work underscores the transformative potential of Ag-coated SS tubular substrates can be used as an efficient cathode current collector, enhancing contact resistance, offering a promising route in developing next-generation SOEC.

An effective power input is essential for achieving high-performance electrolysis in water splitting, characterised by a high hydrogen production rate and low energy consumption. This study investigates the optimisation of electrochemical performance in a novel hybrid manganese cycle by employing a superimposed pulsation technique to enhance hydrogen generation and realise " Power-to-Manganese-toGas ". The electrolysis system was comprised of a proton exchange membrane (PEM) incorporated with the Mn/MnSO 4 redox pair to facilitate efficient water splitting. The electrochemical performance measurements of the cell revealed that elevated cell voltages enhance the charge acquisition of Mn 2+ ions more than protons, thereby improving manganese recovery efficiency. However, this also introduces higher non-Faradaic losses, resulting in an increase in the specific energy consumption and a decrease in the overall energy conversion efficiency. The application of a superimposed pulse—featuring a peak voltage of 5.6 V and a base voltage of 3.5 V—proved beneficial in maintaining cathodic protection, supporting ion replenishment, reducing current oscillations, and sustaining the hydrogen evolution reaction. Moreover, pulse frequency was found to significantly influence productivity, while the duty cycle had a marked impact on improving current efficiency (99.43 %), overall energy conversion efficiency (37.11 %), manganese content (28.50 %), and other performance metrics. A duty cycle of 50 % at 50 Hz was identified as optimal , reducing specific energy consumption by 4.33 % compared to the conventional direct current operation.

This study reports the reaction mechanism and electrolyte optimisation aspects of a novel low-temperature water-splitting system developed for the efficient production of hydrogen based on the Mn–MnSO4 redox pair. The system incorporates an electrolysis step and an Mn2+ ion recovery step for splitting water in a cyclic operation. Two steps operate within similar temperature ranges, enabling tight integration and efficient heat exchange. The optimisation of electrolytes for the electrolysis step was first carried out in a proton-exchange membrane (PEM) H-cell. The experiments were figured out using a three-factor case study based on the factorial design approach, incorporating temperature, concentration, and pH value as the main variables. Subsequently, machine learning models were employed to analyse the data and predict the best pairing of electrolytes by systematically exploring the critical ratio of conductivity to potential. The results showed that at a cell voltage of 5.0 V and 40 °C, the ratio of importance between the conductivity and MEDR potential is 1:9 for the catholyte, while the anolyte ratio of importance between the conductivity and OER potential is 6:4. Accordingly, the optimal electrolyte composition was found to be a combination of MnSO4 solution (1.64 mol/L; pH 2.86) with H2SO4 (25.25 wt%). Also, a remarkable corresponding current efficiency of 99.25 % was achieved with an overall energy conservation efficiency of 40.15 %. The proposed cycle is the first of its kind developed based on the chemical looping principle and can be potentially applied for large-scale continuous green hydrogen production at a low-levelized cost.. [Display omitted]. •A novel hybrid water-splitting cycle was proposed and validated for H2 production.•A factorial design approach was applied to optimise the electrolyte properties.•The two-stage current and cell-voltage mechanism were identified.•An unprecedented current efficiency showed great potential for scale up.

Gadolinium-doped ceria (GDC) is a promising electrolyte material for developing solid oxide fuel cells (SOFCs) because it offers a higher ionic conductivity at the intermediate operating temperature. In this work, nanocrystalline GDC (Ce1-xGdxO2-x/2, where x = 0.1 and 0.2) powders were synthesised through a novel co-precipitation synthesis method (benzoate route) using ammonium benzoate as a low-cost precipitant. The effect of the synthesis route and processing variables (calcination temperatures and time) on the microstructural and electrical properties of the resulting GDC powder was studied systematically. Multiple GDC electrolyte pellets were fabricated by pressing the GDC powders, followed by sintering the samples at 1100 °C for 6 h. The ionic and electronic conductivity of the GDC pellets were measured in air using EIS at different temperatures (450–750 °C). Huggins' model was used to determine the ionic and electronic conductivity of the GDC pellets. The fabricated electrolyte pellets showed a high relative density of 98.31and 99.02 % for the pre-calcined non-washed and pre-calcined washed powders, respectively, with a crystal size lower than 12 nm. Among all samples, the GDC electrolyte pellet fabricated using the pre-calcined washed powder exhibited the highest ionic conductivity of 3.63E-01 S cm−1 at 750 °C and activation energy of 0.52 eV with an average crystal size of 7–8 nm. The results of this study help to understand and design more efficient ceramic fuel cells with controlled microstructure and compositions at a lower cost.