Three-dimensional interconnected metal foam-supported Co3O4 nanoarrays for highly efficient hydrogen production via ammonia decomposition

Nickel foam (NF) has been recognized to have great application potential in catalysis. In this study, cobalt oxide (Co 3 O 4 ) nanoarrays were synthesized on NF using a hydrothermal method and applied for carbon oxide-free (CO X -free) production via ammonia (NH 3 ) decomposition at atmospheric pressure. The application of varying hydrothermal temperatures from 80 °C to 180 °C enabled the synthesis of Co 3 O 4 nanostructured arrays with diverse morphologies, presenting a novel approach to catalyst design. Among the synthesized catalysts, the optimal Co/NF-120-8 nanoarray catalyst synthesized with the hydrothermal temperature of 120 °C achieved 100 % NH 3 conversion under a WHSV of 12,858 ml g cat −1 h −1 at 625 °C and maintained its activity for 45 h without noticeable degradation. SEM, TEM and XRD characterization results demonstrated that the hydrothermal temperature significantly influenced the morphologies, crystallite size and microstructure of the prepared catalysts, thereby affecting their catalytic performance for NH 3 decomposition. XPS and H 2 -TPR measurements further indicated that the most abundant metallic Co and lattice oxygen were the key factors for the superior performance of NH 3 decomposition over Co/NF-120-8 catalyst. Such a monolithic nanoarray catalyst proposed herein may open a new window in the efficient hydrogen production via NH 3 decomposition and may also serve as a promising material in other heterogeneous reactions.