Periodic Reporting for period 3 - PHOENEEX (Pyrolytic Hierarchical Organic Electrodes for sustaiNable Electrochemical Energy Systems)
Période du rapport: 2021-05-01 au 2022-10-31
Motivation
The development of compact microelectronic systems such as portable wireless sensors, smart cards or implantable devices is booming, driven by the increasing importance of the Internet of Things (IoT). As a consequence, the demand for miniaturised power sources is growing rapidly. The next generation of compact energy systems should not only provide safe operation, long time stability, low cost and high energy efficiency, but also be based on sustainable materials and technologies to minimise the impact on our ecosystem. Biophotovoltaic systems (BPVs) have been proposed as biobatteries for sustainable energy conversion and storage1. BPVs use living organisms such as cyanobacteria to harvest light energy and deliver electrical outputs. As a particular advantage, these systems are capable of self-repair, reproduction, and are even able to store energy for power generation in the dark. In portable microelectronic systems, typically peak currents of several mA and peak output power of a few mW are required for sensor measurements and wireless signal transmission. Although research over the last few years has resulted in dramatic increases in peak power densities in BPVs, the maximum reported so far is around 10µW/cm2 with current densities in the order of a few 100 µA/cm2. This means that miniaturised BPVs with a size of a few cm2 would currently be unable to supply sufficient energy for portable devices. In parallel, microsupercapacitors (µSCs) have emerged as promising candidates for storage of electrical energy in microchips and portable systems.
Novelty
As the main novelty of PHOENEEX we will develop the BioCapacitor Microchip – a holistic approach combining energy harvesting in miniaturised BPVs with energy storage in µSCs on a single platform meeting the energy and power requirements of portable microelectronic systems. For electrochemical energy conversion in BPVs and electrochemical energy storage in µSCs the integration of microelectrodes with well-defined geometry, excellent electrical and electrochemical properties and high chemical stability is essential. In PHOENEEX, we currently investigate novel approaches for the fabrication of 3D carbon microelectrodes (3DCMEs) with highly tailored material properties, large surface area and hierarchical architecture using pyrolysis. In this process, patterned polymer precursors are exposed to high temperatures (> 900 °C) in inert atmosphere (N2 or Ar) and converted into pyrolytic carbon. We will apply the 3DCMEs to i) considerably improve the efficiency of energy harvesting in BPV cells and ii) enhance temporal storage of the harvested energy in µSCs.
Project hypotheses and objectives
The overall aim of PHOENEEX is to develop a miniaturized energy system for portable devices combining energy conversion in BPVs with energy storage in µSCs on a single platform. The fundamental project hypothesis is that the combination of novel precursor materials, new methods for 3D polymer microfabrication and optimised pyrolysis processes will allow for fabrication of 3DCMEs with highly tailored material properties, large surface area and hierarchical architecture impossible to obtain with any other method. The tailored 3DCMEs will improve the electrochemical energy harvesting in BPV cells and enhance energy storage in µSCs. The combination of optimised BPV cells and µSCs on a miniaturised energy platform will allow to meet the power and energy requirements of microelectronic systems. The main project objectives are
i) to fabricate highly porous or fractal-like pyrolysed carbon electrodes with large surface area
ii) to develop new methods for fabrication of hierarchical 3DCMEs with tailored geometry,
iii) to demonstrate direct laser writing of carbon microelectrodes on polymer substrates
iv) to integrate 3DCMEs as anodes in cyanobacteria-based BPV cells for improved energy harvesting
v) to integrate 3DCMEs with novel IDE configurations and porous materials in µSCs for improved energy storage
vi) to develop the BioCapacitor Microchip, a first demonstrator of a miniaturised sustainable energy platform combining BPV cells and µSCs.
The development of compact microelectronic systems such as portable wireless sensors, smart cards or implantable devices is booming, driven by the increasing importance of the Internet of Things (IoT). As a consequence, the demand for miniaturised power sources is growing rapidly. The next generation of compact energy systems should not only provide safe operation, long time stability, low cost and high energy efficiency, but also be based on sustainable materials and technologies to minimise the impact on our ecosystem. Biophotovoltaic systems (BPVs) have been proposed as biobatteries for sustainable energy conversion and storage1. BPVs use living organisms such as cyanobacteria to harvest light energy and deliver electrical outputs. As a particular advantage, these systems are capable of self-repair, reproduction, and are even able to store energy for power generation in the dark. In portable microelectronic systems, typically peak currents of several mA and peak output power of a few mW are required for sensor measurements and wireless signal transmission. Although research over the last few years has resulted in dramatic increases in peak power densities in BPVs, the maximum reported so far is around 10µW/cm2 with current densities in the order of a few 100 µA/cm2. This means that miniaturised BPVs with a size of a few cm2 would currently be unable to supply sufficient energy for portable devices. In parallel, microsupercapacitors (µSCs) have emerged as promising candidates for storage of electrical energy in microchips and portable systems.
Novelty
As the main novelty of PHOENEEX we will develop the BioCapacitor Microchip – a holistic approach combining energy harvesting in miniaturised BPVs with energy storage in µSCs on a single platform meeting the energy and power requirements of portable microelectronic systems. For electrochemical energy conversion in BPVs and electrochemical energy storage in µSCs the integration of microelectrodes with well-defined geometry, excellent electrical and electrochemical properties and high chemical stability is essential. In PHOENEEX, we currently investigate novel approaches for the fabrication of 3D carbon microelectrodes (3DCMEs) with highly tailored material properties, large surface area and hierarchical architecture using pyrolysis. In this process, patterned polymer precursors are exposed to high temperatures (> 900 °C) in inert atmosphere (N2 or Ar) and converted into pyrolytic carbon. We will apply the 3DCMEs to i) considerably improve the efficiency of energy harvesting in BPV cells and ii) enhance temporal storage of the harvested energy in µSCs.
Project hypotheses and objectives
The overall aim of PHOENEEX is to develop a miniaturized energy system for portable devices combining energy conversion in BPVs with energy storage in µSCs on a single platform. The fundamental project hypothesis is that the combination of novel precursor materials, new methods for 3D polymer microfabrication and optimised pyrolysis processes will allow for fabrication of 3DCMEs with highly tailored material properties, large surface area and hierarchical architecture impossible to obtain with any other method. The tailored 3DCMEs will improve the electrochemical energy harvesting in BPV cells and enhance energy storage in µSCs. The combination of optimised BPV cells and µSCs on a miniaturised energy platform will allow to meet the power and energy requirements of microelectronic systems. The main project objectives are
i) to fabricate highly porous or fractal-like pyrolysed carbon electrodes with large surface area
ii) to develop new methods for fabrication of hierarchical 3DCMEs with tailored geometry,
iii) to demonstrate direct laser writing of carbon microelectrodes on polymer substrates
iv) to integrate 3DCMEs as anodes in cyanobacteria-based BPV cells for improved energy harvesting
v) to integrate 3DCMEs with novel IDE configurations and porous materials in µSCs for improved energy storage
vi) to develop the BioCapacitor Microchip, a first demonstrator of a miniaturised sustainable energy platform combining BPV cells and µSCs.
During the first two years of the project, we mainly focused on development of the technological foundation for the project. This both included the purchase and establishment of research infrastructure (PHOENEEX-Lab) and research in WP1-WP3 on novel strategies for fabrication of pyrolytic carbon electrodes addressing objective i)-iii) described above. Furthermore, the cyanobacteria cultures were transferred from the University of Cambridge (UC) to DTU.
WP1: Pyrolysis of various polymer precursors was investigated to allow for understanding of the link between polymer precursor structures and the resulting pyrolytic carbon materials.
WP2: Novel strategies for fabrication of highly 3D carbon microelectrodes (3DCMEs) were explored. For this purpose, additive manufacturing (3D printing) has been combined with pyrolysis. Furthermore, a process for fabrication of multi-layered 3DCMEs based on maskless UV photolithograph was developed.
WP3: A novel process for selective laser pyrolysis of a polymer precursor modified with an absorber was proposed and optimized.
WP1: Pyrolysis of various polymer precursors was investigated to allow for understanding of the link between polymer precursor structures and the resulting pyrolytic carbon materials.
WP2: Novel strategies for fabrication of highly 3D carbon microelectrodes (3DCMEs) were explored. For this purpose, additive manufacturing (3D printing) has been combined with pyrolysis. Furthermore, a process for fabrication of multi-layered 3DCMEs based on maskless UV photolithograph was developed.
WP3: A novel process for selective laser pyrolysis of a polymer precursor modified with an absorber was proposed and optimized.
In the last three years of the project, the main focus will be on development of the actual electrochemical energy systems and their combination in a single platform, addressing objectives iv)-vi) mentioned above.