A High-Performance Hydrogen Generation System: Transition Metal-Catalyzed Hydrolysis of Ammonia–Borane

How do we unlock hydrogen safely and efficiently for tomorrow’s clean energy systems? This presentation dives into an innovative approach: using ammonia–borane (NH₃BH₃) and transition metal catalysts to produce hydrogen on demand, under simple room-temperature conditions. With platinum-based catalysts showing outstanding results, the study demonstrates how catalyst structure and particle size directly impact performance. Complete hydrogen release was achieved, confirmed by analytical methods such as NMR, TEM, and mass spectrometry. These findings push forward the possibilities of hydrogen storage, portable fuel systems, and sustainable energy technologies.

1. S.P Alahapperuma A high-performance hydrogen generation system: Transition metal-catalyzed dissociation and hydrolysis of ammonia–borane

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3. Contents Introduction Methodology Results And Discussion Conclusion Reference Acknowledgment 2

4. 01 Introduction 3

5. The Need for Clean Hydrogen Generation Hydrogen as a clean energy carrier for fuel cell applications Critical challenges in hydrogen storage and on-demand generation Portable fuel cell systems require safe, efficient hydrogen sources Chemical hydrides provide ambient-temperature H₂ on demand. Room-temperature catalytic hydrolysis is a promising route. 4

6. Why Ammonia Borane (NH₃BH₃)? Highest hydrogen content: 19.6 wt.% hydrogen Ambient stability: Solid at room temperature, air-stable Safety advantages: Non-toxic, non-flammable Chemical compatibility: Compatible with fuel cell systems Theoretical yield: 3 mol H₂ per mol NH₃BH₃ 5

7. Limitations of Prior Approaches 1 Few catalysts reach theoretical 3 H₂/AB at room temperature. E.g. High-temperature pyrolysis: Requires 137°C, energy intensive 2 Existing systems slow (>10 min) or incomplete (<3 H₂). 3 Need to correlate Pt particle size/dispersion with activity. Hydrogen Storage Media Comparison Storage Medium H₂ Capacity (wt%) Remarks Compressed H₂ Gas ~4–5% Low gravimetric capacity; bulky tanks Liquid H₂ ~7.8% Energy-intensive cryogenic cooling Metal Hydrides 1–3% Heavy; low storage efficiency Complex Hydrides 4–12% Still lower than AB; high temps required LOHCs ~5–6% Lower energy density; slow kinetics Adsorbents (MOFs, etc.) <2% Very low capacity; lab-scale only 6

8. Objectives 1 Screen transition-metal catalysts for AB hydrolysis. Quantify kinetics & Hydrogen yield. 2 Characterize structure–activity correlations. 3 Evaluate recyclability, safety, and application potential. 4 7

9. 02 Methodology 8

10. Materials 1 Ammonia–borane (90 %, Aldrich). 2 Catalysts: Pt black, 20 wt % Pt/C, 40 wt % Pt/C, PtO₂, K₂PtCl₄, Rh-dimer, Pd black, RuO₂, W, Au₂O₃, IrO₂, Ag₂O. 9

11. Reaction Apparatus 1 Two-neck round-bottom flask under argon. Gas burette for volumetric H₂ measurement. 2 Addition funnel for AB solution. 3 Magnetic stirring; room temperature (20–25 °C). 4 10

12. Technique Purpose Instrument ¹¹B NMR Boron speciation JEOL JNM-AL400 (128 MHz) TEM Particle morphology Hitachi H-9000NA (200 kV) MS Identify evolved gas Balzers Prisma QMS 200 pH Solution pH Glass electrode Analytical Techniques 11

13. Preparation & Reaction Setup 12

14. Analytical Procedures TEM Analysis: Prepare dried catalyst residues for transmission electron microscopy (TEM) imaging to observe particle morphology and size. 11 B NMR Spectroscopy: Take a portion of the filtrate. Add D₂O to the sample for instrument locking. Place the solution in a 5mm outer diameter NMR tube, using a coaxial insert containing BF₃·(C₂H₅)₂O as an external reference. Record spectra at 128.15MHz and report chemical shifts in ppm relative to the reference. pH Measurement: Measure and record the pH of the filtrate. Mass Spectrometry: Analyze the evolved gas using a mass spectrometer (e.g., Balzers Prisma QMS 200) to confirm the presence of hydrogen (H₂). 13

15. 03 Results & Discussion 14

16. 11 B NMR spectra 15 11 B NMR spectra of (a) aqueous NH 3 BH 3 solution (0.33wt.%) freshly prepared, (b) after 30 days following (a) under Ar atmosphere, and (c) after reaction (25min) of (a) in the presence of Pt black. The peak at 0 ppm is due to the external reference BF 3 ·(C 2 H 5 ) 2 O

17. Hydrogen Evolution from NH₃BH₃ with Various Catalysts 16 Hydrogen release from aqueous NH 3 BH 3 (0.33wt.%) solution in the presence of various metal catalysts (metal/NH 3 BH 3 =0.018).

18. Hydrogen Release: Pt Catalyst Comparison Pt/C catalysts (20 wt.% and 40 wt.%) show the highest activity due to high Pt dispersion. 20 wt.% Pt/C completes hydrogen release in under 2 minutes. PtO₂ is more active than Pt black, likely from better dispersion and reducibility. Pt black acts slower, requiring more time for full H₂ release. K₂PtCl₄ shows the lowest activity and slow conversion. 17 Hydrogen release from aqueous NH 3 BH 3 solution (0.33wt.%) in the presence of (a) 20wt.% Pt/C, (b) 40wt.% Pt/C, (c) PtO 2 , (d) Pt black and (e) K 2 PtCl 4 . The amount of Pt is normalized to Pt/NH 3 BH 3 =0.018

19. TEM Micrographs after NH₃BH₃ Reaction 18 TEM micrographs for (a) 20wt.% Pt/C, (b) 40wt.% Pt/C, (c) PtO 2 , (d) Pt black and (e) K 2 PtCl 4 after reaction with aqueous NH 3 BH 3 (0.33wt.%). Scales indicate 10nm in (a) and (b), and 50nm in (c)–(e)

20. Catalytic Performance of 20 wt.% Pt/C with Varying [NH₃BH₃] 19 Hydrogen release from aqueous NH3BH3 solutions with different concentrations in the presence of 20wt.% Pt/C with the catalyst amount kept unchanged: (a) 0.33wt.% (Pt/NH3BH3 =0.018), (b) 1.0wt.% Pt/NH3BH3 =0.0059) and (c) 5.0wt.% (Pt/NH3BH3 =0.0012)

21. Summary of the analytical results Analytical Technique Key Observations Significance/Interpretation Gas Burette (H₂ Measurement) 20% Pt/C: Full H₂ release (<2 min); slower with other catalysts Confirms fastest hydrogen evolution with Pt/C ¹¹B NMR Spectroscopy Rapid loss of NH₃BH₃ peaks; borate peaks appear Demonstrates complete, efficient substrate conversion Mass Spectrometry Evolved gas >99% pure H₂ Confirms hydrogen as only gaseous product TEM (Microscopy) 20% Pt/C: Small, well-dispersed Pt; 40% Pt/C: Larger, agglomerated Pt Fine dispersion critical for high catalytic activity pH Monitoring pH rises slightly (from ~9 to ~10) during reaction Near-neutral pH: safe and favorable for fuel cell use Catalyst Recyclability 20% Pt/C retains activity ≥5 cycles Indicates robust, reusable catalyst 20

22. 04 Conclusion 21

23. Key Outcomes Demonstrated efficient hydrogen generation from ammonia borane at room temperature using transition metal catalysts. 20 wt% Pt/C catalyst: Fastest reaction (<2 min), highest performance. Achieved complete conversion: 3 mol H₂ per mol NH₃BH₃ (8.9 wt% H₂ yield). Reaction proceeds rapidly and under mild, near-neutral pH conditions. 22

24. Mechanistic Implications & Practical Relevance Analytical studies (¹¹B NMR, MS, TEM) confirmed: Full substrate conversion; hydrogen as sole product. Finer Pt particle dispersion yields higher activity. Catalyst shows good recyclability and operational stability. Ammonia borane system is safer and more practical (ambient conditions, safer pH) than alternatives like sodium borohydride. 23

25. Future Directions Need for development of non-noble, earth-abundant metal catalysts to lower cost. Further research into: Catalyst lifetime and recycling. Management and regeneration of ammonia and spent borate. System-level optimization for real-world fuel cell applications. 24

26. References Chandra, M. and Xu, Q., 2006. A high-performance hydrogen generation system: Transition metal-catalyzed dissociation and hydrolysis of ammonia–borane.  Journal of Power Sources , 156(2), pp.190-194. Demirci, U.B. and Miele, P., 2009. Sodium borohydride versus ammonia borane, in hydrogen storage and direct fuel cell applications.  Energy & Environmental Science , 2(6), pp.627-637. Catalytic Hydrogen Generation through Ammonia Borane Hydrolysis using Cu-MOF-74, 2024.  Energy & Fuels , 38(10), pp.8968-8978. Formation of a Key Intermediate Complex Species in Catalytic Hydrolysis of NH₃BH₃ by Bimetal Clusters, 2020.  Frontiers in Chemistry , 8, p.604. Portable Power Generation for Remote Areas Using Hydrogen Generated via Maleic Acid-Promoted Hydrolysis of Ammonia Borane, 2019.  Energies , 12(21), p.4074. 25

27. Thank You ! 29