Background
Efficient, durable, and low-cost CO2 conversion requires integration of components which enables efficient transport and minimal resistance to the catalytic reactions at the electrodes. Challenges in electrolyser operation at the high current density required for practical applications include: (1) Access of CO2 to active catalyst sites, (2) Chemical and mechanical stability of components, and (3) High energy and economic costs of CO2 capture and product separation.
Aims
To identify and develop new electrode architectures and fabrication routes for integrated electrolyser designs via a deep understanding of gas/liquid/solid interfaces, mass and charge transport mechanisms and kinetics.
Outcomes
Fundamental understanding of the structure and dynamic stability of electrical double layers and gas bubbles will guide electrocatalyst, electrode and electrolyser designs, with knowledge translatable into other disciplines such as colloid and interface science. Outcomes are expected to inform other fields including fuel cells, photo(electro)catalysts for water splitting and microfluidics.
RT1A: Managing gas and liquid transport in electrolysers
Project Lead – Professor Yansong Shen
State-of-the-art CO2 electrolysers use GDEs to enhance CO2 transport from the feed gas to the liquid electrolyte and active catalyst to accelerate reactions. However, high current densities cause electrolyte flooding of the gas diffusion layer (GDL),8 impeding CO2 diffusion. This project will develop advanced numerical models to understand and predict gas and liquid behaviour in the electrode structure and the electrolyser. We will also design and fabricate GDEs with tailored porosity and surface hydrophobicity to reduce flooding in electrolysers.
RT1B: Novel electrode and electrolyser designs and fabrication methods
Project Lead – Professor John Zhu
This research theme will focus on the design and development of novel electrodes and efficient electrolyzers for high-rate electrochemical CO2 reduction. Gas-diffusion electrodes (GDEs) in planar and microtubular (hollow fiber) shapes with tuned properties such as high active surface area, conductivity, CO2 delivery, etc. will be fabricated from different catalysts based on the desired product(s). The catalyst layer deposition parameters and composition of the catalyst ink (such as catalyst-ionomer-solvent interactions) will be optimized to achieve selective and stable CO2 electrolysis at high current densities. Moreover, patterned electrodes prepared via 3D printing will be demonstrated to assess the potential of this approach to fabricate electrodes of desired materials on a larger scale with high uniformity. Further, the mechanism and microenvironment of GDEs will be studied, aiming for the selective production of more valuable products such as ethylene, and a better understanding of the variables during the fabrication steps. In particular, microtubular electrodes have a flow-through CO2 delivery regime, unlike flow-by in conventional planar ones, which results in higher chances for the formation of triple-phase interfaces and interaction between the electrolyte and CO2, thereby their mechanism will be explored in detail through in-situ techniques such as Raman and Mass Spectroscopy.
RT1C: Protocols for electrolyser testing, design, and scale-up
Project Lead – Professor Tom Rufford
CO2 electrolysis research and rapidly emerging CO2 conversion industries lack reliable and standardised testing protocols required for robust evaluations to guide business and policy decisions. Some guidelines are available for batch H-type cells,15 but there is little guidance for continuous, bench-scale electrolysers (1-5 cm2 electrode areas), let alone pilot-scale electrolysers (m2 areas). To address this urgent need, we will develop new experimental protocols in Years 1-2 for CO2 electrolyser testing that consider active areas of cathodes, anodes and membranes (often unreported); product composition and flow rates (many papers do not measure effluent gas flowrates); flooding rates; and electrochemical testing cycles. Along with the catalyst screening protocols (RT2A), the electrolyser testing protocols will be structured to provide critical information to design multiple electrolyser cells and stacks, and provide inputs to technoeconomic analysis and life cycle assessment mirroring standards and methods for battery and proton-exchange membrane fuel cell testing.
RT1D: Design of Cu-based cathodes and electrolyser
Project Lead – Professor Zaiping Guo
Cu-based cathodes will be optimized to improve the reaction dynamics and enhance reduction selectivity by introducing species such as NH2-, CH3-CH2- species, single atoms, COF, MOF, etc. to Cu. In situ characterization will be conducted to monitor the catalyst structure change and the intermediates. The stacked flowing-type electrolyser will be optimized with stable performance and efficient product separation techniques.
RT1E: Electrochemical Process Design and Technology Adoption
Project Lead – Associate Professor Simon Smart