Oral_Presentation_Hassan_Mabrak_TURKEY-2024 modified.pptx

Green hydrogen is emerging as a vital element in the global transition toward sustainable energy. In a recent congress focused on renewable energy solutions, I had the opportunity to present a study on the production and storage capacity of green hydrogen, highlighting its potential to revolutionize energy systems.

The presentation began by outlining the fundamentals of green hydrogen. Produced by the electrolysis of water using renewable energy sources like wind or solar power, green hydrogen is a clean, zero-emission alternative to fossil fuels. This makes it a key player in decarbonizing industries such as transportation, manufacturing, and energy production, which are currently responsible for large carbon footprints.

In the first section of the presentation, I delved into the production of green hydrogen. The process of electrolysis, though well-established, still faces significant challenges regarding efficiency and cost. For green hydrogen to become commercially viable on a global scale, advancements in electrolyzer technologies are crucial. My presentation reviewed various electrolyzer types, including alkaline, proton exchange membrane (PEM), and solid oxide electrolyzers, discussing their efficiencies, operating conditions, and potential for scaling up. The use of surplus renewable energy to drive electrolysis was emphasized as a strategic approach to improving cost-effectiveness and enhancing the sustainability of energy grids.

The second part of the presentation focused on hydrogen storage, one of the most critical aspects of deploying green hydrogen at scale. Hydrogen's low energy density per unit volume, especially under ambient conditions, poses a significant challenge for both storage and transportation. I presented various storage methods, such as compressed hydrogen, liquid hydrogen, and solid-state storage using metal hydrides. Each method has its own advantages and drawbacks in terms of energy density, safety, and cost. For instance, while compressed hydrogen storage is the most widely used, it requires high-pressure tanks that can be expensive and raise safety concerns. On the other hand, liquid hydrogen storage provides a higher energy density but requires cryogenic temperatures, which complicates the infrastructure.

During the congress, much attention was given to the integration of hydrogen storage systems with renewable energy sources. I highlighted innovative approaches such as underground storage in salt caverns, which can provide large-scale, long-term storage solutions for regions with appropriate geological formations. Such strategies are essential for ensuring that hydrogen can be stored efficiently and released when demand peaks or renewable energy supply fluctuates.

The Q&A session following the presentation brought to light the audience's growing interest in green hydrogen's potential to contribute to a circular energy economy.

1. Advancements in Water Electrolysis: Catalyst Development and Efficiency Enhancements for Sustainable Hydrogen Production Hassan MABRAK, Siham ELMAZOUZI, Ghandi Youssef, El Bahrami Wadiae , Driss TAKKY, Youssef NAIMI. [email protected] [email protected] [phone]

2. Introduction

3. Hydrogen production methods Fig. 1. Methods of hydrogen production

4. Hydrogen production methods Table 1 - Hydrogen color shades and their Technology, cost, and CO2 emissions.

5. Fig. 2. Major hydrogen production methods and applications

6. advantages of water electrolysis

7. main forms of water electrolysis In general, the literature identifies three main forms of water electrolysis: alkaline water electrolysis, acidic or Proton Exchange Membrane (PEM) electrolysis, and high-temperature Solid Oxide (SO) Electrolysis Alkaline electrolysis PEM electrolysis HT electrolysis Anodic oxidation Cathodic reduction Anodic oxidation Cathodic reduction   Anodic oxidation Cathodic reduction Alkaline electrolysis PEM electrolysis HT electrolysis Table 2 - Half-equations for the three types of electrolysis

8. Fig. 3. Schematic illustration of alkaline water electrolysis working principle. A lkaline water electrolysis Advantages : • Well established Technology • Commercialized for industrial applications • Noble metal -free electrocatalysts • Relatively low cost • Long- term stability Disadvantages : • Limited current densities • Crossover of the gasses • High concentrated (5M KOH) liquid electrolyte

9. Fig. 4. Schematic view of PEM water electrolysis working principle. PEM water electrolysis Advantages : • Commercialized technology • Operates higher current densities • High purity of the gases • Compact system design • Quick response Disadvantages • Cost of the cell components • Noble metal electrocatalysts • Acidic electrolyte

10. Fig. 5 . Schematic view of solid oxide water electrolysis working principle. S olid oxide water electrolysis Advantages : • High working temperature • High efficiency Disadvantages : • Limited stability • Under development

11. Mechanism of the Hydrogen Evolution Reaction (HER) Hydrogen Evolution Reactions (HER) Environnement Mechanism Volmer-Heyrovsky reactions   Acidic     Alcalin   Volmer reaction Heyrovsky reaction   Volmer reaction Heyrovsky reaction Volmer-Tafel reaction Acidic and Alcalin Tafel reaction Hydrogen Evolution Reactions (HER) Environnement Mechanism   Acidic     Alcalin   Volmer reaction Heyrovsky reaction   Volmer reaction Heyrovsky reaction Acidic and Alcalin Tafel reaction Table 3 - Hydrogen evolution reaction (her) mechanisms (based on volmer-heyrovsky or volmer-tafel mechanisms). Where * represents a vacant active site, and H* represents a hydrogen atom attached to active sites.

12. Fig. 6. Mechanism of the Hydrogen Evolution Reaction (HER) in (a) acidic solution and (b) alkaline solution

13. Electrocatalysts used in HER Noble metals such as platinum (Pt), palladium (Pd), iridium (Ir), ruthenium (Ru), and rhodium (Rh) are commonly employed in the hydrogen adsorption reaction due to their ability to provide active sites for this process

14. Non-precious metal HER electrocatalysts for AWE Electrocatalytic material Overvoltage (V) Power density (A/cm²) References Ni/Co Ni/Mo Ni/Mn NiCoP NiSFe Ni 2 P NPs MnNiP 2 NiS/MoS/C Co 2 PNRS MoS 2 /Ti MoS 2 /C 3 N 4 - - - 0.107 0.222 0.138 0.138 0.117 0.045 0.108 0.153 0.001 0.010 0.010 0.010 0.010 0.010 0.010 0.010 0.010 0.010 0.010 [64] [65] [65] [66] [67] [68] [69] [70] [71] [72] [73] Table 4 - Non-precious electrocatalysts for HER in alkaline solutions of 1 mol/l NaOH and KOH.

15. Non-precious metal HER electrocatalysts for AWE Fig. 7 . Morphological images and characterization of the Nix-Cox alloy: (a) Ni morphological images, (b) Ni 72 -Co 28 morphological images, (c) Ni 58 -Co 42 morphological images, and (d) Co morphological image

16. Non-precious electrocatalysts for HER in proton exchange membrane electrolysis of water (PEME) Studies have shown that catalysts based on palladium supported on tungsten carbide or molybdenum carbide have shown similar performance to platinum, with a reduction in metal loadings and operating costs . Alternatives such as MoS 2 and MoO 3 have been explored, but have lower current densities than conventional platinum cathodes .

17. Non-precious electrocatalysts for HER in SOEC Fig. 8. The schematic and electrochemical principle of Ni-YSZ based anode. However, Ni-YSZ has low stability and requires a high concentration of hydrogen to prevent oxidation of the nickel, leading to agglomeration of the metal at high temperatures

18. C haracteristics Fig. 9 . The I-V characteristics of three types of electrolyzers. Hu et al, using parameter analyses in COMSOL Multiphysics, obtained I-V curves for three types of electrolyzer, as shown in Figure 9

19. Conclusion In conclusion, the hydrogen production landscape is deeply rooted in the growing need for a clean, sustainable energy source, imposed by global environmental and energy challenges. Hydrogen presents itself as a crucial alternative energy carrier, thanks to its ability to be produced from renewable raw materials and electricity generated by clean sources Precious and non-precious metal catalysts play an essential role in water electrolysis. Precious metals, such as platinum, have high electrocatalytic activity, but are expensive. Non-precious metals, such as nickel and iron, present more affordable alternatives and are showing interesting performances. Research is focused on finding economical and efficient solutions for electrocatalysts to make water electrolysis more competitive. The superior performance of systems such as SOEC and PEM, as demonstrated by their I-V curves and operational parameters, corroborates the importance of optimizing temperature, ionic conductivity and applied voltages to maximize efficiency and productivity in electrolysis.