Green activation using reducing agents of carbon-based 3D printed electrodes: Turning good electrodes to great

3D printing of carbon-based nanocomposites, which combine the electrical properties of carbon additives with the benefits of thermoplastics, has emerged as a promising route towards rapid and low-cost manufacturing of customised-shaped electronic devices with minimised waste. However, their poor electrical activity in their pristine state makes activation post-treatments mandatory to reduce the amount of insulating polymer. These post-treatments typically involve the use of toxic organic solvents or costly thermal annealing methods. Herein, a simple eco-friendly wet-chemical post-treatment is presented for the quick and general activation of carbon-based 3D printed electronic devices by employing reducing agents like ascorbic acid or sodium borohydride. We tested a range of reducing agents, such as sodium borohydride, lithium aluminium hydride, hydrazine and ascorbic acid, as well as a model oxidising agent like hydrogen peroxide. We found that ascorbic acid and sodium borohydride are the most effective chemicals to achieve electrically active devices while preserving the shape and structure of the 3D printed carbon objects. Thus, this work allows the development of advanced carbon-based 3D printed electrodes by employing an eco-friendly activation approach.