Design and synthesis of a nickel–chromium alloy catalyst for hydrogen generation from hydrazine monohydrate

Abstract

The catalytic decomposition of hydrazine monohydrate has garnered considerable interest as an on-demand hydrogen generation technology for vehicular and mobile applications. However, existing hydrazine decomposition catalysts often suffer from high cost or poor catalytic performance. We herein report a combined experimental and theoretical study of nickel–chromium (Ni–Cr) alloy as an efficient catalyst for hydrogen generation from hydrazine monohydrate. Our DFT calculations revealed that, compared to pure Ni, Ni–Cr alloying results in an upward shift of the d-band center relative to the Fermi level, thus offering an opportunity to improve the activity for hydrazine decomposition. To experimentally verify this theoretical prediction, we synthesized a hierarchically nanostructured catalyst composed of tiny Ni₃Cr alloy nanoparticles embedded within a composite matrix of nanocrystalline NiO and amorphous CrO_x using a hydrothermal method combined with reductive annealing treatment. Consistent with the theoretical calculations, the Ni₃Cr/NiO–CrO_x catalyst demonstrated a fivefold increase in activity compared to Ni/NiO–CrO_x. Notably, Ni₃Cr/NiO–CrO_x exhibited a favorable combination of high activity, 100% selectivity and excellent stability, with less than 4% activity loss and no significant decrease in H₂ selectivity after 10 cycles. Using this noble-metal-free catalyst, we further developed a hydrazine-based hydrogen generation system with a hydrogen capacity as high as 6.2 wt% and a fast dynamic response.