J. Clean. Prod. http://doi.org/4rn (2015)

The current standard material for transparent electrodes in liquid-crystal displays for smart phones and other devices with transparent screens is indium tin oxide (ITO). Owing to the chemical instability of ITO, and the high cost and scarcity of indium, graphene has been proposed as a potential substitute. However, it remains unclear how such a substitution will impact energy use and metal resources. Rickard Arvidsson and colleagues at Chalmers University of Technology in Sweden have now shown that replacing ITO with graphene may be beneficial because energy use during graphene production could be lower than that during ITO production. The substitution may, however, bring about other effects.

The researchers used the well-established life-cycle assessment method to examine the energy and scarce metal requirements of producing a graphene electrode by chemical vapour deposition and compared it with the production of ITO. During chemical vapour deposition, to form graphene on a catalytic surface such as copper, an excess of methane gas is heated, and the study found that methane use is the main contributor to energy consumption during graphene production. Comparing global reserves, indium and tin are likely to be scarcer than copper. The researchers suggest that while copper availability is unlikely to restrain graphene production — even though the use of copper during graphene production is about 300 times higher than the use of indium and tin in ITO production — current copper consumption is unsustainable. Depending on whether replacement of ITO with graphene will increase the use of liquid-crystal displays or contribute to other new graphene-based technologies, net energy use in society may increase or decrease.