3D Printing for Electrochemical Energy Applications.

Additive manufacturing (also known as three-dimensional (3D) printing) is being extensively utilized in many areas of electrochemistry to produce electrodes and devices, as this technique allows for fast prototyping and is relatively low cost. Furthermore, there is a variety of 3D-printing technologies available, which include fused deposition modeling (FDM), inkjet printing, select laser melting (SLM), and stereolithography (SLA), making additive manufacturing a highly desirable technique for electrochemical purposes. In particular, over the last number of years, a significant amount of research into using 3D printing to create electrodes/devices for electrochemical energy conversion and storage has emerged. Strides have been made in this area; however, there are still a number of challenges and drawbacks that need to be overcome in order to 3D print active and stable electrodes/devices for electrochemical energy conversion and storage to rival that of the state-of-the-art. In this Review, we will give an overview of the reasoning behind using 3D printing for these electrochemical applications. We will then discuss how the electrochemical performance of the electrodes/devices are affected by the various 3D-printing technologies and by manipulating the 3D-printed electrodes by post modification techniques. Finally, we will give our insights into the future perspectives of this exciting field based on our discussion through this Review.

Versatile Design of Functional Organic-Inorganic 3D-Printed (Opto)Electronic Interfaces with Custom Catalytic Activity.

The ability to combine organic and inorganic components in a single material represents a great step toward the development of advanced (opto)electronic systems. Nowadays, 3D-printing technology has generated a revolution in the rapid prototyping and low-cost fabrication of 3D-printed electronic devices. However, a main drawback when using 3D-printed transducers is the lack of robust functionalization methods for tuning their capabilities. Herein, a simple, general and robust in situ functionalization approach is reported to tailor the capabilities of 3D-printed nanocomposite carbon/polymer electrode (3D-nCE) surfaces with a battery of functional inorganic nanoparticles (FINPs), which are appealing active units for electronic, optical and catalytic applications. The versatility of the resulting functional organic-inorganic 3D-printed electronic interfaces is provided in different pivotal areas of electrochemistry, including i) electrocatalysis, ii) bio-electroanalysis, iii) energy (storage and conversion), and iv) photoelectrochemical applications. Overall, the synergism of combining the transducing characteristics of 3D-nCEs with the implanted tuning surface capabilities of FINPs leads to new/enhanced electrochemical performances when compared to their bare 3D-nCE counterparts. Accordingly, this work elucidates that FINPs have much to offer in the field of 3D-printing technology and provides the bases toward the green fabrication of functional organic-inorganic 3D-printed (opto)electronic interfaces with custom catalytic activity.

A rational design for the selective detection of dopamine using conducting polymers.

Poly(N-methylpyrrole) (PNMPy), poly(N-cyanoethylpyrrole) (PNCPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) films have been prepared using both single and two polymerization steps for the selective determination of low concentrations of dopamine, ascorbic acid and uric acid in tertiary mixtures. Analysis of the sensitivity and resolution parameters derived from the electrochemical response of such films indicates that PEDOT is the most appropriate for the unambiguous detection of the three species. Indeed, the performance of PEDOT is practically independent of the presence of both gold nanoparticles at the surface of the film and interphases inside the film, even though these two factors are known to improve the electroactivity of conducting polymers. Quantum mechanical calculations on model complexes have been used to examine the intermolecular interaction involved in complexes formed by PEDOT chains and oxidized dopamine, ascorbic acid and uric acid. Results show that such complexes are mainly stabilized by C-HO interactions rather than by conventional hydrogen bonds. In order to improve the sensitivity of PEDOT through the formation of specific hydrogen bonds, a derivative bearing a hydroxymethyl group attached to the dioxane ring of each repeat unit has been designed. Poly(hydroxymethyl-3,4-ethylenedioxythiophene) (PHMeDOT) has been prepared and characterized by FTIR, UV-vis spectroscopy, cyclic voltammetry, scanning electron microscopy and atomic force microscopy. Finally, the performance of PHMeDOT and PEDOT for the selective detection of the species mentioned above has been compared.

Polyoxometalate-Enhanced 3D-Printed Supercapacitors.

The contemporary critical energy crisis demands the fast and cost-effective preparation of supercapacitors to replace old-fashioned batteries. 3D-printing has been established as a fast, cheap, and reliable new manufacturing technique that enables the preparation of such devices.. Unfortunately, carbon-based filaments used in 3D printing lack the necessary electrical properties to build supercapacitors by themselves and have to be combined with other materials to reach their full potential. In this study, carbon-based 3D-printed carbon electrodes (3D-PCE) have been combined with two polyoxometalates (that share the same redox cluster) by drop casting of the inorganic cluster mixed with a conducting slurry. The modified electrodes show higher capacitances than reference carbon electrodes showing the exceptional properties of the polyoxometalates. Moreover, the different nature of the polyoxometalate counter ions allows for their distinct deposition, giving rise to a different coverage of the surface of the 3D-PCE. The different coverage and the nature of the interaction of the counter ion with the electrolyte significantly modify the capacitance and resistance of the materials, playing a key role that should not be overlooked during their preparation.

Bistable (Supra)molecular Switches on 3D-Printed Responsive Interfaces with Electrical Readout.

Molecular switching memories have gained great importance in recent years because of the current sharp increase in the production of consumer electronics. Herein, 3D-printed nanocomposite carbon electrodes (3D-nCEs) have been explored as unconventional responsive interfaces to electrically readout bistable molecular switches via electrochemical impedance spectroscopy as the output system. As a proof-of-concept, two different 3D-printed responsive interfaces have been devised using surface engineering for covalently anchoring (supra)molecular components that well-define two electrical states (on/off) driven by either electrical or optical stimuli. Accordingly, this work paves the way for the functionalization of 3D-nCEs through fundamental chemistry, opening up new horizons in unprecedented tailored 3D-printed responsive interfaces which could be utilized as potential (bio)sensors, (opto)electronic devices, or molecular logic gates.

Tailoring capacitance of 3D-printed graphene electrodes by carbonisation temperature.

3D-printing is an emerging technology that can be used for the fast prototyping and decentralised production of objects with complex geometries. Concretely, carbon-based 3D-printed electrodes have emerged as promising components for electrochemical capacitors. However, such electrodes usually require some post-treatments to be electrically active. Herein, 3D-printed nanocomposite electrodes made from a polylactic acid/nanocarbon filament have been characterised through different carbonisation temperatures in order to improve the conductivity of the electrodes via insulating polymer removal. Importantly, the carbonisation temperature has demonstrated to be a key parameter to tailor the capacitive behaviour of the resulting electrodes. Accordingly, this work opens new insights in advanced 3D-printed carbon-based electrodes employing thermal activation.