Bimetallic NiIr nanoparticles supported on lanthanum oxy-carbonate as highly efficient catalysts for hydrogen evolution from hydrazine borane and hydrazine

Abstract

Recently, the utilization of hydrazine borane (N₂H₄BH₃) and hydrous hydrazine (N₂H₄·H₂O) as promising hydrogen carriers has received increasing research interest. In this work, NiIr alloy nanoparticles (NPs) immobilized on lanthanum oxy-carbonate (NiIr/La₂O₂CO₃) have been successfully synthesized through a sodium–hydroxide-assisted reduction approach at room temperature. It was found that ultrafine NiIr NPs with an average size of around 2.3 nm were effectively and highly dispersed on La₂O₂CO₃. NiIr/La₂O₂CO₃ nanocomposites (NCs) prepared with the assistance of NaOH showed much higher catalytic activity and H₂ selectivity toward the N₂H₄BH₃ dehydrogenation reaction as compared to those of NiIr/La₂O₂CO₃–N prepared without addition of NaOH. Among all of the tested samples, the optimized Ni_0.75Ir_0.25/La₂O₂CO₃ NCs exhibited the highest catalytic performance with 100% hydrogen selectivity for hydrogen generation from an aqueous solution of N₂H₄BH₃. The total turnover frequency (TOF) of Ni_0.75Ir_0.25/La₂O₂CO₃ NCs for this dehydrogenation reaction was found to be 1250 h⁻¹ at 323 K, which is among the highest values ever reported. Additionally, this catalyst also exhibited a remarkable catalytic performance for efficient and complete decomposition of N₂H₄·H₂O. This excellent catalytic performance could be attributed to the high dispersion of metal NPs and the strong interaction between the metal and support as well as the promotion effect of NaOH.