During the course of UP-GREEN we have successfully implemented our previously developed protocols
of
electrochemical exfoliation of graphite into high quality graphene and further optimized the
procedures towards higher quality and/or larger production rates. In one approach we have employed
the use of radical scavengers to minimize the effect of oxidation via hydroxyl-radicals that are
generated while water-splitting during the exfoliation process (EU patent). However we found this
process slightly difficult to upscale which is why an alternative production process was developed
that uses an alternating exfoliation current. In this way two graphite electrodes can be exfoliated
simultaneously whereas by switching the potential alternating oxidative and reductive environments
are introduced on their surface. This switching between oxidizing and reducing conditions during
exfoliation helps to reduce oxidative damage to the graphene, while the simultaneous exfoliation of
both electrodes can increase the exfoliation rate to around 15g electrochemically exfoliated
graphene (EG) per hour on a lab scale equipment.[1]
Improvement of the exfoliation equipment allowed us to reach production rates of up to 25-48 g/h
using a semi- continuous process with recycling of the electrolyte and possibility of continuous
feeding of fresh graphite electrodes. Although a fully automated and continuously running
exfoliation equipment could not be realized during the course of the project (due to unavailability
of suitable “off-the-shelf” equipment like filters etc.) the exfoliation rate of 48 g/h marks a
significant increase. Extrapolated to a continuous operation the production rate would be >1100
g/day, thus even slightly exceeding the 1 kg/day goal that was set in the project.
The EG produced during the project was furthermore successfully implemented in different
applications fields, such as electrodes in organic solar cells[2], ink-jet printing[3], energy
storage devices[4,5] and as a template for the growth of other 2D materials[6]. Additionally the
concept of electrochemical exfoliation was adopted to the preparation of high-surface area graphite
electrodes that served well as templates and support for the growth and/or deposition of active
materials for catalysis applications such as water splitting.[7-9]
Finally, the promising results led to the creation of a spin-off company from TU Dresden, that will
continue to improve and commercialize the process.
1. Ultrafast Delamination of Graphite into High-Quality Graphene Using Alternating Currents, Yang, Sheng; Ricciardulli, Antonio Gaetano; Liu, Shaohua; et al. ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 2017, 56(23), 6669-6675
2. Solution-Processable High-Quality Graphene for Organic Solar Cells, Ricciardulli, Antonio Gaetano; Yang, Sheng; Feng, Xinliang; et al. ACS APPLIED MATERIALS & INTERFACES 2017, 9(30), 25412-25417
3. Scalable Fabrication and Integration of Graphene Microsupercapacitors Through Full Inkjet Printing, J. Li, S. Sollami Delekta, P. Zhang, S. Yang, M. R. Lohe, X. Zhuang, X. Feng, M. Ostling, ACS Nano 2017, 11, 8249-8256.
4. Stimulus-Responsive Micro-Supercapacitors with Ultrahigh Energy Density and Reversible Electrochromic Window, P. Zhang, F. Zhu, F. Wang, J. Wang, R. Dong, X. Zhuang, O. G. Schmidt, X. Feng, Adv Mater 2017, 29, 1604491.
5. Flexible All-Solid-State Supercapacitors with High Volumetric Capacitances Boosted by Solution Processable MXene and Electrochemically Exfoliated Graphene, H. Li, Y. Hou, F. Wang, M. R. Lohe, X. Zhuang, L. Niu, X. Feng, Advanced Energy Materials 2017, 7, 1601847.
6. Graphene-coupled nitrogen-enriched porous carbon nanosheets for energy storage, J. Zhu, X. Zhuang, J. Yang, X. Feng, S.-i. Hirano, J. Mater. Chem. A 2017, 5, 16732-16739.
7. Integrated Hierarchical Cobalt Sulfide/Nickel Selenide Hybrid Nanosheets as an Efficient Three-dimensional Electrode for Electrochemical and Photoelectrochemical Water Splitting, Hou, Yang; Qiu, Ming; Nam, Gyutae; et al. NANO LETTERS 2017, 17(7), 4202-4209
8. Electrocatalysts: Recent Advances in Earth-Abundant Heterogeneous Electrocatalysts for Photoelectrochemical Water Splitting, Y. Hou, X. Zhuang, X. Feng, Small Methods 2017, 1, 1700090.
9. Ternary Porous Cobalt Phosphoselenide Nanosheets: An Efficient Electrocatalyst for Electrocatalytic and Photoelectrochemical Water Splitting, Y. Hou, M. Qiu, T. Zhang, X. Zhuang, C. S. Kim, C. Yuan, X. Feng, Adv Mater 2017, DOI: 10.1002/adma.201701589.
