Graphene as metal-free catalyst for aqueous phase reforming of ethylene glycol

Graphene obtained by pyrolysis of alginate shows in the absence of any metal, catalytic activity towards the decomposition of ethylene glycol into hydrogen and carbon dioxide at 250 °C due to the presence of hydrogenating/dehydrogenating sites. This reaction has interest in the context of valorization of waste waters from cellulose depolymerization and it is typically catalyzed by platinum and other transition metals. In this regard, the use of graphene as metal-free catalyst may have a considerable advantage from the point of sustainability of the catalyst. Based on the influence of the presence of acids and bases and the lack of influence of quenchers of reactive oxygen species, it is proposed that the active sites on the graphene could be frustrated acid-base Lewis pairs acting as dehydrogenating centers. Controls with oxalic acid and glyoxal have shown that if ethylene glycol is converted into these α-dicarbonylic compounds, spontaneous decarboxylation would occur totally (oxalic acid) or in some extent (glyoxal. 30%). In the last case, decarboxylation is also assisted by graphene.