H2 production by CH4 decomposition over CuNiAl-LDH catalyst without thermal pretreatment

: Hydrogen is an important energy carrier in the transition toward lower-carbon energy systems. Methane decomposition offers a route to produce H 2 while co-producing structured carbon, including carbon nanotubes (CNTs), without forming CO 2 as a direct reaction product. This study evaluated CuNiAl-layered double hydroxides (LDH) for CH 4 decomposition and examined the effects of calcination and H 2 reduction. The as-synthesized LDH was compared with its calcined (NiO) and H 2 -reduced (NiO-R) forms. Samples were characterized by N 2 adsorption–desorption, XRD, H 2 -TPR, TPO, and FE-SEM. Activity tests were conducted in a fixed-bed reactor with online gas chromatography, with stepwise temperature tests (500–700 °C) and time-on-stream (TOS) tests. TOS tests of LDH showed the highest average conversion at 600 °C (59%), but activity loss occurred, while at 550 °C, LDH maintained 52% conversion with negligible deactivation over 300 min. The activity loss at 600 °C coincided with graphitic carbon formation and crystallite growth. In the 550 °C TOS comparison, NiO-R showed lower average conversion (47%) than the LDH in the same temperature. Sintering was associated with deactivation in the NiO-R sample. These results show that LDH can sustain CH 4 conversion under CH 4 flow without prior calcination or H 2 reduction, avoiding the energy demand associated with calcination and H 2 consumption during catalyst pretreatment.