Efficient hydrogen production from ethanol steam reforming over layer-controlled graphene-encapsulated Ni catalysts

• Published in: Journal of cleaner production 2020-04, Vol.252, p.119907, Article 119907
• Main Authors: Chen, Dong, Liu, Chenlong, Mao, Yangyang, Wang, Wenju, Li, Tianle
• Format: Article
• Language: English
• Subjects: Density functional theory; Ethanol steam reforming; Graphene defects; H2 production; Ni catalyst; Steam-assisted control
• ISSN: 0959-6526; 1879-1786
• DOI: 10.1016/j.jclepro.2019.119907

Large-scale synthesis and applications of graphene-encapsulated metal catalysts remain a great challenge since it is difficult to control the thickness of graphene layers. In this study, graphene-encapsulated Ni nanoparticles (Ni@Gr) were fabricated via in-situ growth method. Steam-assisted control was carried out to decrease the graphene layer number. The layer-controlled Ni@Gr catalyst consisted of Ni core and graphene shell. The anchored metal was well defended against oxidation or acid etching. In addition, the influence of steam-gasification temperature on the nature of catalysts was also investigated. The catalyst obtained via steam-assisted control at 800 °C (Ni@Gr800) possessed excellent textural features, such as thinner graphene shell, more defects on the surface. Consequently, Ni@Gr800 catalyst presented superior initial activity and durability in the steam reforming of ethanol, especially at 550 °C. By density functional theory calculations, the presence of defects improved the adsorption energy of all reaction species. The carbonaceous deposition was the primary reason for catalyst deactivation. Textural features of Ni@Gr800 contributed to the formation of carbon filaments, which facilitated coke gasification on the catalyst. This work provides a procedure for controlling the graphene layer number of catalysts with graphene as the covering, and an approach to fabricate defects on the graphene surface. •A novel strategy to encapsulate Ni within ultrathin graphene layers is presented.•Steam-assisted control is carried out to regulate the graphene layer number.•The graphene layers can protect the inner metal from oxidation or acid etching.•The catalyst layer-controlled at 800 °C shows superior ESR activity and durability.