A sustainable approach to large area transfer of graphene and recycling of the copper substrate

Abstract

Graphene, the prototypical two-dimensional material, has been a subject of much interest and extensive studies in the past few decades. Carbon dioxide, on the other hand, has gained infamy because of global climate change concerns. In this Communication, we demonstrate an unlikely but useful marriage between these two ostensibly juxtaposing carbon-containing compounds. Specifically, we address the challenges in sustainable graphene manufacturing by developing a new route for graphene transfer and reuse of the copper catalyst substrate via carbonic acid enabled electrochemical under-etching delamination. Electrochemical reduction of the cuprous oxide (Cu₂O) interlayer between the copper catalyst substrate and the chemical vapour deposition (CVD) synthesized surface layer graphene is achieved by using carbon dioxide as the precursor for making a conductive carbonic acid electrolyte. This under-etching delamination approach to graphene transfer mitigates the conventional need for harsh chemical etchants that otherwise expend the copper catalyst. This approach also removes the need for the concomitant multiple subsequent rinsing steps typically needed for chemical etching or delamination via salt/alkali based electrolytes, thereby significantly reducing the process water usage. In addition, we also show the application of using food-grade ethyl cellulose as the thin film handle layer for the transfer process. This inexpensive and environmentally benign alternative for the polymeric thin film replaces the conventionally used high grade polymers that are typically solvated in harsh solvents. We expect our development to enable more environmentally sustainable and cost-effective strategies for the large-scale integration of graphene and analogous 2D materials and their devices, and also to generate new application streams for value-added uses of industrially captured carbon dioxide.