Catalytic decomposition of methane using Ni and Cu/hydroxyapatite catalysts: Toward sustainable hydrogen and carbon nanomaterials production

The catalytic decomposition of methane has been studied in an effort to upgrade methane into an important energy vector: hydrogen. The products of this reaction are essentially high-purity H 2 and solid carbon. In addition, the appropriate reaction conditions can influence the morphology of the carbon that is generated, allowing carbon nanotubes (CNTs) to be obtained, which have important commercial value. Nevertheless, the development of catalysts that are resistant to deactivation remains a challenge. The reverse microemulsion method has been employed to synthesize catalysts to produce materials with high metallic dispersion and nanometric particles. The present study aims to investigate the use of reverse microemulsion in the synthesis of Ni and Cu catalysts supported on hydroxyapatite (HAP) for converting methane into low-carbon H 2 and filamentous carbon (CNFs/CNTs) via catalytic decomposition. To this end, a reverse microemulsion system was used in the synthesis of Ni/HAP and Cu-Ni/HAP catalysts. The catalysts were then evaluated in the catalytic decomposition of methane in the temperature range of 500–800 °C. The characterizations showed that catalysts with good metal dispersion and thermal stability were obtained. The addition of Cu promoted the stability of the catalyst, and the Cu-Ni/HAP catalyst showed the best methane conversion, with an average conversion of 60% at 700 °C, a hydrogen yield of 69%, and formation of filamentous carbon with a tip growth mechanism. These results are similar to those reported in the literature, but with a significantly lower metal loading, which allows the advancement of studies related to the catalytic decomposition of methane that consider small or moderate metal loading with highly dispersed nanometric particles.