Cobalt nanoparticle catalysed graphitization and the effect of metal precursor decomposition temperature

Abstract

Porous carbon foams hold great promise for supercapacitors and next generation energy storage materials but greater control over the formation of the pore structure would aid the development of these materials. High temperature graphitization has been investigated as a sustainable method of producing these technologically important materials and the addition of transition metals is known to promote the formation of graphitic carbon and potentially control the pore structure, however the effect of different metal precursors has rarely been examined. Using different cobalt salts, specifically Co(OAc)₂, CoCl₂ and Co(NO₃)₂, in a dextran/TritonX-45 aerogel graphitization, the foams produced were analyzed using Raman spectroscopy, XRD, thermal analysis, gas sorption and various electron microscopy techniques. These revealed that when using salts with low thermal stability such as Co(NO₃)₂ and Co(OAc)₂ the metal nanoparticles are formed rapidly and become trapped in the carbon matrix causing uniform graphitization. In contrast, when stable salts are used such as CoCl₂ the carbon decomposes before metal reduction and large metal crystals, microns in size, are formed. This control of nanoparticle size through understanding the thermal stability of metal precursors should be general to other widely used reagents to inform the rational design and production of future functional materials.