In situ neutron imaging of MnCl2 -silica gel systems for ammonia storage

Ammonia is gaining interest as a carbon-free hydrogen carrier, creating a need for efficient storage technologies compatible with emerging low-temperature synthesis routes. Among solid-phase sorbents, MnCl 2 dispersed on silica gel has demonstrated promising ammonia uptake, yet the behavior of larger-scale sorbent beds remains poorly understood. In this study, in situ neutron imaging was used to investigate ammonia sorption-desorption cycling in scaled-up MnCl 2 -silica gel beds, providing non-destructive, in situ visualization of ammonia transport, and structural changes. Sorbents containing 34 wt% (wp34) and 46 wt% (wp46) MnCl 2 were examined over four cycles. Observed ammonia uptake increased with cycling, with wp46 exhibiting faster and greater uptake. Neutron imaging revealed limited agglomeration and good dimensional stability in wp34 but particle suspension was seen, whereas wp46 formed large agglomerates that partially broke down during cycling and experienced approximately 20% irreversible sample bed expansion. These findings highlight critical material and structural considerations for developing robust, scalable ammonia sorption systems.