Simona Borta

The need to reduce greenhouse gas emissions and guarantee a stable and reliable energy supply has resulted in an increase in the demand for sustainable energy storage solutions over the last decade. Rechargeable batteries with solid-state electrolytes (SSE) have become a focus area due to their potential for increased energy density, longer cycle life, and safety over conventional liquid electrolytic batteries. The superionic sodium conductor (NASICON) Na₃Zr₂Si2PO₁₂ has gained a lot of attention among ESS because of its exceptional electrochemical properties, which make it a promising candidate for solid-state sodium-ion batteries. NASICON’s open frame structure makes it possible to transport sodium ions efficiently even at room temperature, while its wide electrochemical window enables high-voltage operation and reduces side reactions, resulting in safer battery performance. Furthermore, NASICON is more compatible with sodium ion systems, can help with electrode interface issues, and is simple to process. The characteristics of NASICON make it a highly desirable and vital material for solid-state sodium-ion batteries. The aim of this study is to prepare and characterize ceramic membranes that contain Na_3.06Zr₂Si₂PO₁₂ and Na_3.18Zr₂Si₂PO₁₂, and measure their stability in seawater batteries that serve as solid electrolytes. The surface analysis revealed that the Na_3.06Zr₂Si₂PO₁₂ powder has a specific surface area of 7.17 m² g⁻¹, which is more than the Na_3.18Zr₂Si₂PO₁₂ powder’s 6.61 m² g⁻¹. During measurement, the NASICON samples showed ionic conductivities of 8.5 × 10⁻⁵ and 6.19 × 10⁻⁴ S cm⁻¹. Using platinum/carbon (Pt/C) as a catalyst and seawater as a source of cathodes with sodium ions (Na⁺), batteries were charged and discharged using different current values (50 and 100 µA) for testing. In an electrochemical cell, a battery with a NASICON membrane and Pt/C catalysts with 0.00033 g platinum content was used to assess reproducibility at a constant current of 2 h. After 100 h of operation, charging and discharging voltage efficiency was 71% (50/100 µA) and 83.5% (100 µA). The electric power level is observed to increase with the number of operating cycles.

Pt on carbon black (Pt/C) has been widely used as a catalyst for both ORR and hydrogen oxidation reaction (HOR), but its stability is compromised due to carbon corrosion and catalyst poisoning, leading to low Pt utilization. To address this issue, this study suggests replacing carbon black with graphene in the catalyst layer. The importance of this work lies in the detailed examination of novel electrocatalysts with high electrocatalytic activity for large-scale power generation. In this paper, we discuss the use of regulatory techniques like structure tuning and composition optimization to construct nanocatalysts impregnated with noble and non-noble metals on graphene supports. Finally, it highlights the limitations and advantages of these nanocatalysts along with some future perspectives. Our objective is that this summary will help in the research and rational design of graphene-based nanostructures for efficient ORR electrocatalysis. The results of this study showed that the performances of graphene-based catalysts show high electrochemical active surface areas for Pt-Fe/GNPs and Pt-Ni/GNPs catalysts (132 and 136 m² g⁻¹, respectively) at 100 operating cycles. Also, high current densities and power densities were observed for Pt₃-Ni/G and Pt-Co/G catalysts used at the cathode. The values for current density were 1.590 and 1.779 A cm⁻², respectively, while the corresponding values for power density were 0.57 and 0.785 W cm⁻².

Rechargeable batteries play a crucial role in the utilization of renewable energy sources. Energy storage systems (ESSs) are designed to store renewable energy efficiently for immediate use. The market for energy storage systems heavily relies on lithium-ion batteries due to their high energy density, capacity, and competitiveness. However, the increasing cost and limited availability of lithium make long-term use challenging. As an alternative to Li-ion batteries, rechargeable seawater batteries are gaining attention due to their abundant and complementary sodium ion active materials. This study focuses on the preparation and characterization of Na_3.0Zr₂Si₂PO₁₂- and Na_3.15Zr₂Si₂PO₁₂-type ceramic membranes and testing their stability in seawater batteries used as solid electrolyte. From the surface analysis, it was observed that the Na_3.15Zr₂Si₂PO₁₂ powder showed a specific surface area of 2.94 m²/g compared to 2.69 m²/g for the Na_3.0Zr₂Si₂PO₁₂ powder. The measured NASICON samples achieved ionic conductivities between 7.42 × 10⁻⁵ and 4.4 × 10⁻⁴ S/cm compared to the NASICON commercial membrane with an ionic conductivity of 3.9 × 10⁻⁴ S/cm. Battery testing involved charging/discharging at various constant current values (0.6–2.0 mA), using Pt/C as the catalyst and seawater as the catholyte.

This paper presents the preparation of heterogeneous catalysts for the direct hydrogenation process of CO₂ to methanol. The development of the modern chemical industry is inextricably linked to the use of catalytic processes. As a result, currently over 80% of new technologies introduced in the chemical industry incorporate catalytic processes. Since the basic factor of catalytic processes is the catalysts, the studies for the deepening of the knowledge regarding the nature of the action of the catalysts, for the development of new catalysts and catalytic systems, as well as for their improvement, represent a research priority of a fundamental or applied nature. The Cu/ZnO/Al₂O₃ catalyst for the synthesis of green methanol, using precursors of an inorganic (copper nitrate, denoted by Cu/ZnO/Al₂O₃-1) and organic (copper acetate, denoted by Cu/ZnO/Al₂O₃-2) nature, are obtained by chemical impregnation that includes two stages: preparation and one of calcination. The preparation methods and conditions, as well as the physico-chemical properties of the catalyst precursor, play a major role in the behavior of the catalysts. The prepared catalysts were characterized using atomic adsorption analysis, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, specific surface area and pore size analyses, adsorption, and the chemisorption of vapor (BET).

In the present work, we studied the impact of excess Na addition on the structure of the standard NASICON ion conductor along with Na ion transport mechanisms. In this sense, NASICON ceramic membranes (NZSP) were prepared by a simple chemical synthesis method, the solid state reaction (SSR), using an excess of 5% Na (Na_3.15Zr₂Si₂PO₁₂) and an excess of 10% Na (Na_3.3Zr₂Si₂PO₁₂), in order to improve the conduction properties of the ceramic membrane. The characterization of the NZSP nanoparticles was performed by measuring the particle size by dynamic light scattering (DLS), the morphology of the NASICON samples pre-sintered at 1100 °C was analyzed by the SEM method (scanning electron microscope), and X-ray diffraction (XRD) analysis was used to investigate the crystal structure of samples, while the surface area was measured using the BET technique. The electrical properties (i.e., ionic conductivity) were evaluated by impedance spectroscopic methods at room temperature (RT). Following the experiments for NASICON membranes without Na excess, with 5% Na excess, and with 10% Na excess synthesized at different pressing forces and sintering temperatures, it was found that membranes with a 10% Na excess, sintered at 1175 °C for 10 h, presented a good ionic conductivity (4.72 × 10⁻⁴ S/cm).