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"Hugo, Pieter"
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Energy comparison of sequential and integrated CO2 capture and electrochemical conversion
Integrating carbon dioxide (CO
2
) electrolysis with CO
2
capture provides exciting new opportunities for energy reductions by simultaneously removing the energy-demanding regeneration step in CO
2
capture and avoiding critical issues faced by CO
2
gas-fed electrolysers. However, understanding the potential energy advantages of an integrated process is not straightforward due to the interconnected processes which require knowledge of both capture and electrochemical conversion processes. Here, we identify the upper limits of the integrated process from an energy perspective by comparing the working principles and performance of integrated and sequential approaches. Our high-level energy analyses unveil that an integrated electrolyser must show similar performance to the gas-fed electrolyser to ensure an energy benefit of up to 44% versus the sequential route. However, such energy benefits diminish if future gas-fed electrolysers resolve the CO
2
utilisation issue and if an integrated electrolyser shows lower conversion efficiencies than the gas-fed system.
Coupling CO
2
capture and electrolysis offers new opportunities to reduce energy cost. Here, the authors identify that the integrated electrolyser must show similar performance to the gas-fed electrolyser to ensure an energy benefit of up to 44% versus sequential capture and conversion processes.
Journal Article
Non-invasive current collectors for improved current-density distribution during CO2 electrolysis on super-hydrophobic electrodes
Electrochemical reduction of CO
2
presents an attractive way to store renewable energy in chemical bonds in a potentially carbon-neutral way. However, the available electrolyzers suffer from intrinsic problems, like flooding and salt accumulation, that must be overcome to industrialize the technology. To mitigate flooding and salt precipitation issues, researchers have used super-hydrophobic electrodes based on either expanded polytetrafluoroethylene (ePTFE) gas-diffusion layers (GDL’s), or carbon-based GDL’s with added PTFE. While the PTFE backbone is highly resistant to flooding, the non-conductive nature of PTFE means that without additional current collection the catalyst layer itself is responsible for electron-dispersion, which penalizes system efficiency and stability. In this work, we present operando results that illustrate that the current distribution and electrical potential distribution is far from a uniform distribution in thin catalyst layers (~50 nm) deposited onto ePTFE GDL’s. We then compare the effects of thicker catalyst layers (~500 nm) and a newly developed non-invasive current collector (NICC). The NICC can maintain more uniform current distributions with 10-fold thinner catalyst layers while improving stability towards ethylene (≥ 30%) by approximately two-fold.
Electrolysis of carbon dioxide holds great promise in providing a sustainable pathway for hydrocarbon fuels. In this work, the authors show the effect of current distribution on super-hydrophobic electrodes that avoid flooding and present a solution fit for the scale-up of these systems.
Journal Article
Local ionic transport enables selective PGM-free bipolar membrane electrode assembly
Bipolar membranes in electrochemical CO
2
conversion cells enable different reaction environments in the CO
2
-reduction and O
2
-evolution compartments. Under ideal conditions, water-splitting in the bipolar membrane allows for platinum-group-metal-free anode materials and high CO
2
utilizations. In practice, however, even minor unwanted ion crossover limits stability to short time periods. Here we report the vital role of managing ionic species to improve CO
2
conversion efficiency while preventing acidification of the anodic compartment. Through transport modelling, we identify that an anion-exchange ionomer in the catalyst layer improves local bicarbonate availability and increasing the proton transference number in the bipolar membranes increases CO
2
regeneration and limits K
+
concentration in the cathode region. Through experiments, we show that a uniform local distribution of bicarbonate ions increases the accessibility of reverted CO
2
to the catalyst surface, improving Faradaic efficiency and limiting current densities by twofold. Using these insights, we demonstrate a fully platinum-group-metal-free bipolar membrane electrode assembly CO
2
conversion system exhibiting <1% CO
2
/cation crossover rates and 80-90% CO
2
-to-CO utilization efficiency over 150 h operation at 100 mA cm
−2
without anolyte replenishment.
Here, authors report that local ionic transport across cathode catalyst layers is vital in improving CO production from CO
2
. This work demonstrates the potential of a CO
2
electrolyzer constructed from materials free from platinum group metals.
Journal Article
Blockchain technology in commercial real estate transactions
Purpose
The transaction process of an office building is known to be time consuming and inefficient, in part due to the lack of market transparency. The purpose of this paper is to focus on the development of a blockchain application that can improve the transaction process of office buildings in the Netherlands.
Design/methodology/approach
Conducting design science research, the current transaction process of an office building and status quo of blockchain technology in real estate is investigated. Subsequently, multiple parties are interviewed to define major pain points within the process. The interview findings are used to design a blockchain solution which overcomes the aforementioned pain points. After designing, the interviewees are asked again to pragmatically validate the proposed model.
Findings
One of the major pain points identified concerning the transaction process of an office building is that it is difficult to define the characteristics of a property, due to lack of data structure and quality. The proposed application improves the way specific assets are understood by structuring physical and contractual information in one place and guarantees the quality of the data by using the blockchain mechanisms.
Practical implications
A blockchain application is proposed, which can improve the transaction process of an office building.
Originality/value
Recent studies indicate that blockchain technology could lead to improvements in efficiency, transparency and therefore trust within the transaction process. Therefore, the proposed application is of value for the future of real estate data management and the transaction process.
Journal Article
Energy comparison of sequential and integrated CO 2 capture and electrochemical conversion
Integrating carbon dioxide (CO
) electrolysis with CO
capture provides exciting new opportunities for energy reductions by simultaneously removing the energy-demanding regeneration step in CO
capture and avoiding critical issues faced by CO
gas-fed electrolysers. However, understanding the potential energy advantages of an integrated process is not straightforward due to the interconnected processes which require knowledge of both capture and electrochemical conversion processes. Here, we identify the upper limits of the integrated process from an energy perspective by comparing the working principles and performance of integrated and sequential approaches. Our high-level energy analyses unveil that an integrated electrolyser must show similar performance to the gas-fed electrolyser to ensure an energy benefit of up to 44% versus the sequential route. However, such energy benefits diminish if future gas-fed electrolysers resolve the CO
utilisation issue and if an integrated electrolyser shows lower conversion efficiencies than the gas-fed system.
Journal Article
An Optimized Dual-Polarized Quad-Ridges Horn Antenna with Pyramidal Sidewalls
It is well known that quad-ridged horn antennas in general have impedance and radiation characteristics that are significantly worse than that of their double-ridged counterparts. Normally a voltage standing wave ratio (VSWR) of 3 over the operational bandwidth is used for the design specification of quad-ridged horn antennas. The bandwidth of operation is severely restricted due to the excitation of higher order modes in the co-axial to waveguide transition of the antenna. The higher order modes cause a break-up in the radiation pattern of the antenna and large dips in the boresight gain.The performance of the quad-ridged horn antenna with pyramidal sidewalls is improved by separating the antenna into the transition and flared horn sections, and optimizing these sections individually. It is shown that a transition section with a pyramidal cavity and steps, and a flared horn section with an exponential profile with a circular segment for the ridges deliver the best performance. These configurations for the transition and flared horn sections are combined in the complete antenna. The optimized antenna has a 12.5:1 operational bandwidth with improved performance in terms of the VSWR, the coupling between the ports and the boresight gain. A prototype of this antenna is manufactured. Good agreement between the measured and simulated performance is achieved.
Dissertation