Synthesis of graphene blended activated carbon adsorbents for cryo-adsorption vacuum pump application and their thermal conductivity evaluation at 80 K

Abstract Adsorbents play a critical role in cryo-adsorption vacuum pump performance, where activated carbon is favoured for its high surface area, versatile pore structure, chemical stability, and regenerative capacity. Despite these advantages, activated carbon’s low thermal conductivity poses a significant limitation in enhancing the pumping performance of such systems. This study addresses this issue by incorporating graphene, known for its exceptional thermal conductivity, into activated carbon. Unlike other filler materials like metals, which improve thermal properties but degrade the adsorptive capacity of base carbon, graphene can enhance both adsorptive and thermal properties. The research synthesises graphene-blended activated carbon using agglomeration and incipient wetness methods. In agglomeration, graphene is bound to coconut shell-derived activated carbon using carboxymethyl cellulose (CMC), forming pellets that significantly enhance thermal conductivity at Liquid Nitrogen (LN 2 ) temperatures. Specifically, there is a 61% increase for samples with a 0.5% graphene-to-activated carbon weight ratio and a 92% increase for samples with a 1% ratio. In contrast, the incipient wetness method, using activated carbon pellets and graphene oxide dispersion, shows a 69% thermal conductivity improvement for samples with a 1% graphene-to-activated carbon weight ratio. These findings highlight graphene’s potential as a filler material to enhance thermal conductivity in cryo-adsorption vacuum pump applications, thereby improving overall pumping efficiency.