Practical H2 supply from ammonia borane enabled by amorphous iron domain

Abstract

Efficient catalysis of ammonia borane (AB) holds potential for realizing controlled energy release from hydrogen fuel and addressing cost challenges faced by hydrogen storage. Here, we report that amorphous domains on metallic Fe crystal structures (R-Fe₂O₃ Foam) can achieve AB catalytic performances and stability (turnover frequency (TOF) of 113.6 min⁻¹, about 771 L H₂ in 900 h, and 43.27 mL/(min·cm²) for 10×10 cm² of Foam) that outperform reported benchmarks (most <14 L H₂ in 45 h) by at least 20 times. These notable increases are enabled by the stable Fe crystal structure, while defects and unsaturated atoms in the amorphous domains form Fe-B intermediates that significantly lower the dissociation barriers of H₂O and AB. Given that the catalyst lifetime is a key determinant for the practical use in fuel cells, our R-Fe₂O₃ Foam also provides decent H₂ supply (180 mL H₂/min, AB water solution of 7.5 wt% H₂) in a driven commercial car fuel cell at stable power outputs (7.8 V and 1.6 A for at least 5 h). When considered with its facile synthesis method, these materials are potentially very promising for realizing durable high-performance AB catalysts and viable chemical storage in hydrogen powered vehicles.