Polyurethane-scaffolded durable CoB pellet catalyst for continuous hydrogen generation by sodium borohydride hydrolysis

Catalyst durability is a critical factor in developing a large-scale hydrogen production system using continuous sodium borohydride (NaBH 4 ) hydrolysis. To address the mechanical durability issue of the catalyst, we herein developed a polyurethane-scaffolded CoB (CoB/PU) pellet, an organic-inorganic hybrid catalyst that introduced polyurethane as an organic binder to the CoB catalyst. Methylene diphenyl diisocyanate and polyol as raw materials were mixed with pre-synthesized CoB powder, and CoB/PU was fabricated using a sol-gel method and then pelletized under mechanical pressure. The CoB/PU pellets exhibited 1.7 and 1.9 times higher strain and stress at break, respectively, than those of pure CoB pellets. A simulation experiment with a lab-scale hydrogen generation system produced high-purity hydrogen by continuously supplying a 20 wt% NaBH 4 aqueous solution. The CoB/PU pellets showed a catalyst loss of 9.62 wt%. This is a significant improvement over the 95.1 wt% loss observed when using the CoB pellet, confirming the excellent stability and durability of the CoB/PU pellets. In addition, the CoB/PU catalyst consistently maintained a high hydrogen conversion rate of over 90% in nine reuse tests, and stable hydrogen production was possible with an average hydrogen production rate of 0.0159 kg h −1 per each reactor even during 24 h of continuous operation. • CoB/PU pellet catalyst is effective in hydrogen production by NaBH 4 hydrolysis. • CoB/PU is easily prepared by sol-gel, copolymerization, and compression processes. • Polyurethane-scaffolded CoB (CoB/PU) have superior durability than CoB. • CoB/PU maintains hydrogen conversion rate of over 90% in nine repeated use. • CoB/PU shows an average hydrogen production rate of 0.0159 kg h −1 /each for 24 h.