Highly stable hydrotalcite-derived NiCrAl catalyst for methane cracking and directly application for electromagnetic wave absorption

Catalytic cracking of methane is considered a promising route to hydrogen production because no carbon oxides are produced during the reaction. Designing well-stable Ni-based catalysts with long durability and high activity for methane cracking to H 2 and carbon nanomaterials has been a long enormous challenge. Here, high performance NiCr/Al 2 O 3 methane cracking catalyst was prepared by reducing NiCrAl hydrotalcite precursor. The impact on reaction temperature and Cr/Ni ratio on catalytic performance were systematically analyzed. The catalyst with a Cr/Ni ratio of 1:9 showed the best catalytic performance. The catalyst activity decreased while the stability increased with decreasing reaction temperature, and the Ni 2.7 Cr 0.3 Al catalyst was able to stabilize 70 % hydrogen yield at 620 °C for 360 min. Furthermore, it was found that Cr doping reduced the metal grain size, increased the specific surface area of the catalyst, and promoted the reduction of Ni due to the NiCr alloying. In addition, the electromagnetic parameters of the methane cracking spent catalysts with the carbon nanotubes embedding were tested to be shown outstanding impedance matching characteristics at 620 °C, with a minimum reflection loss of −44.5 dB at 15.3 GHz at a thickness of 1.6 mm, and the effective absorption bandwidth reached 4.7 GHz. This paper provides valuable ideas for the design of highly stable methane cracking catalysts and opens a new application direction for spent catalysts as the electromagnetic absorption.