Efficient route to high-quality graphene materials: Kinetically controlled electron beam induced reduction of graphene oxide in aqueous dispersion

Abstract

This work is presenting a highly efficient, cost-efficient and environmentally friendly method for the production of graphene materials (reduced graphene oxide, RedGO) via electron beam (EB) irradiation of aqueous dispersions of graphene oxide (GO). Our strategy here is based on a reduction of GO via EB irradiation under optimally controlled conditions, i.e. dose and dose rate, reducing species, and taking the environmental impact of educt and product into account. The preparation of highly conductive RedGO under these conditions takes only 10-20 minutes at ambient temperature. After our first approach [1], a somewhat similar study was reported by Jung et al. [2] for GO dispersions in H2O/EtOH (50:50). However, the latter route [2], although being similar in spirit, has serious drawbacks for large-scale production because of the formation of acetaldehyde, a very toxic compound, derived from the ethanol in the solvent. The advantages of the present approach compared to [2] are: (i) the use of water as a solvent with only a small content (0.03 - 2 wt.-%) of 2-PrOH allows the scaling-up, since neither 2-PrOH nor its final product acetone are of high technological or environmental concerns; (ii) a much lower dose is required for GO reduction (about 20 vs. 200 kGy, corresponding to only 1/10 of energy consumed); (iii) the conductivity of RedGO is over 60 times higher. Based on the XPS and conductivity measurements, it was established that the EB treatment is leading also to a more efficient reduction of GO compared to the hydrazine method. The highest conductivity in our systems is identical to the best known value of 3 x 104 S/m for RedGO obtained via HI / acetic acid treatment which takes, however, 40 h at 40 oC.