Carbon aerogel is created by freeze drying a solution containing 1wt% of graphene oxide, and 1wt% of either sodium carboxymethyl cellulose (Sigma Aldrich), bacterial cellulose (Sigma Aldrich) or tempo-oxidized cellulose nanofiber (Sigma Aldrich). The procedure to create the aerogel is as follows. 500 µL of the solution is first poured into a PDMS mold, and then frozen on a steel plate that has been pre-cooled by liquid nitrogen. The PDMS mold is required to form the shape of the aerogel, which is a rectangular prism. Once the solution is frozen, the mold is then placed in a flask that is connected to a gas pump. Between the gas pump and the flask is a cold trap filled with liquid nitrogen to condense water vapor and capture it, as well as a valve to disengage the pump when required. The flask is also partially submerged in a 6 ˚C cooling bath.