(Invited) Graphitic Intercalation Compounds: A Versatile Nano-Template for the Synthesis of Multi-Functional Electrocatalysts
Authors: Hof Ferdinand , Boni Alessandro , Valenti Giovanni , Huang Kai , Paolucci Francesco , Penicaud Alain 
Published: February 2020

Bifunctional catalysts, which can perform both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) at low overpotentials with high turnover efficiency (TON) and frequency (TOF), are highly sought after. Platinum group metals are among the best catalysts for both OER and ORR but their scarcity and high cost calls for alternatives. In this context non-precious transition metal and metal oxide are promising options despite their lower intrinsic catalytic activity and chemical stability.1 Carbon nano materials are promising materials for electro catalytic application thanks to their high surface areas, electrical conductivity and stability in acidic or basic aqueous solutions.2

Graphite can be intercalated by potassium forming a graphite intercalation compound (GIC) of defined stages. GICs can be readily exfoliated to monolayer graphene in organic solvents solely by stirring. These graphenide solutions are composed of charged graphene layers and are thermodynamically stable.3,4 In analogy to large flake size graphite, graphitic nano carbons with lateral sizes bellow 50 nm can also be intercalated successfully and can be dissolved in absolute organic solvents. Graphenide solutions have been used in a variety of different applications e.g. to generate transparent conductive films, quantum dots, and surfactant-free graphene in water.5 Additionally, their reducing character has been used to graft functional moieties covalently to the carbon framework.6

In this talk, the exploitation of the reduction potential of graphenide solutions for earth abundant metal nanoparticle generation will be discussed. The advantages of using graphenides as reduction reagent in nanoparticle synthesis are : i) graphenide solutions are strong reducing agents and no additional reducing agent is needed, ii) the redox reaction takes place in close proximity of the carbon lattice and the decoration of the carbon framework thus proceeds efficiently, iii) the amount of reduction agent can be controlled by the concentration of the respective graphenide solution used, iv) the by-product of the reaction is only the respective potassium salt, which can be removed easily.

The resulting composite materials are interesting and promising earth abundant electrocatalysts, due to their structure, small size, morphology and conductive framework. These nanocarbon / metal nanoparticle composite materials exhibit high bifunctional electro catalytic activity towards ORR and OER as well as long term stability.7

Xia, W., et al., (2016) Angew. Chem. Int. Ed. 55, (8) 2650-2676.

Mazzaro, R., et al., (2015) ChemistryOpen 4, (3), 268-273.

Pénicaud, A., et al.,. (2013). Acc. Chem. Res. 46, (1), 129–137.

Vallés, C., et al.. (2008) J. Am. Chem. Soc. 130, 15802–15804.

Bepete, G., et al., (2016) Nat.
Chem.
9, 347–352.

Hof, F., et al., (2014) Chem. - A Eur. J.
20, 16644–16651.

Hof, F., et al., (2017) Chem. - A Eur. J. 23, 15283–15288.