Structure‐Sensitive Steam Reforming of Methane Over Exsolved NiAl‐Layered Double Hydroxides

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Metal exsolution from inorganic compounds is a promising strategy to obtain dispersed nanoparticles stabilized through strong metal‐support interactions. In this work, exsolution of Ni from NiAl‐layered double hydroxide (LDH) produces a well‐defined family of Ni/Al 2 O 3 catalysts for the steam reforming of methane (SRM) to hydrogen. Increasing the calcination temperature of 40 wt% NiAl‐LDH from 400–900 °C (prior to a common reduction protocol) resulted in exsolved Ni nanoparticles of systematically increasing size from 4 to 18 nm diameter on an amorphous alumina support. In contrast, wet‐impregnation of commercial alumina by Ni(NO 3 ) 2 resulted in ∼39 nm Ni nanoparticles at a similar metal loading. SRM exhibited a strong structure‐sensitivity, being favored over smaller particles with 80 % methane conversion and a high specific hydrogen productivity of 0.37 mmol.g −1 Ni .s −1 for Ni particles ≤8 nm at 700 °C, falling to 40 % conversion and 0.08 mmol.g −1 Ni .s −1 for 39 nm particles (for wet‐impregnated Ni/Al 2 O 3 ). Selectivity to H 2 versus CO/CO 2 mirrored this structure‐sensitivity, with smaller Ni particles delivering ≥75% selectivity >450 °C, falling to 65 % over large particles. Exsolved Ni particles derived by 500 °C calcination exhibited excellent stability for at least 24 h time‐on‐stream, with negligible coking, offering Earth‐abundant catalysts for hydrogen production from simple precursors.