Publications
2024
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Insights from techno-economic analysis can guide the design of low-temperature CO₂ electrolyzers towards industrial scaleupShashwati C. Da Cunha, and Joaquin ResascoACS Energy Letters, Oct 2024The field of CO₂ reduction has identified several challenges that must be overcome to realize its immense potential to simultaneously close the carbon cycle, replace fossil-based chemical feedstocks, and store renewable electricity. However, frequently cited research targets were set without quantitatively predicting their impact on the economic viability of CO₂ reduction. Using a physics-informed techno-economic assessment, we offer guidance on the most pressing research priorities for CO₂ reduction based on state-of-the-art electrolyzer performance. We find that the levelized product cost is dominated by the cost of electricity used to drive electrolysis, and the capital cost of the process mostly arises from separations, especially of unreacted CO₂ to be recycled. At a cell resistance as low as 1 Ω·cm² and retail electricity prices, operating at a total current density \textgreater475 mA/cm² drives up electricity demands and increases the cost of producing CO. High current density operation is therefore undesirable unless low cell voltages can be maintained. Although wholesale wind and solar electricity are cheaper than retail electricity, their capacity factors are too low for economical process operation. Adding energy storage to increase the capacity factor of solar electricity triples the capital cost from \34.4 million to \112.6 million for a plant making 50 tCO/day. Improving single-pass conversion is not a priority because it leads to selectivity loss in contemporary membrane electrode assemblies, giving an optimum conversion at \textless15%. To overcome this limitation, we identify the opportunity to modify reactor design to improve CO₂ availability to the catalyst. Decoupling selectivity and single-pass conversion by moving away from a plug flow reactor design, without adding cell voltage, would reduce the base case levelized cost of \1.22/kgCO to \0.97/kgCO and save 36% on capital cost. Finally, we conclude that resolving the “carbonate crossover problem” in neutral electrolytes is not a priority for improving the levelized cost of product.
2023
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Maximizing single-pass conversion does not result in practical readiness for CO2 reduction electrolyzersShashwati C. Da Cunha, and Joaquin ResascoNature Communications, Sep 2023For many chemical processes, high single-pass conversion of reactants into products reduces the need to separate products downstream. However, low-temperature carbon dioxide electrolyzers that maximize single-pass conversion suffer from low product concentration. Maximizing product concentration is therefore a more meaningful target for CO2 electrolyzers than maximizing single-pass conversion.
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The origin of blinking in both mudskippers and tetrapods is linked to life on landBrett R. Aiello, M. Saad Bhamla, Jeff Gau, John G. L. Morris, Kenji Bomar, Shashwati Da Cunha, and 9 more authorsProceedings of the National Academy of Sciences, May 2023Blinking, the transient occlusion of the eye by one or more membranes, serves several functions including wetting, protecting, and cleaning the eye. This behavior is seen in nearly all living tetrapods and absent in other extant sarcopterygian lineages suggesting that it might have arisen during the water-to-land transition. Unfortunately, our understanding of the origin of blinking has been limited by a lack of known anatomical correlates of the behavior in the fossil record and a paucity of comparative functional studies. To understand how and why blinking originates, we leverage mudskippers (Oxudercinae), a clade of amphibious fishes that have convergently evolved blinking. Using microcomputed tomography and histology, we analyzed two mudskipper species, Periophthalmus barbarus and Periophthalmodon septemradiatus, and compared them to the fully aquatic round goby, Neogobius melanostomus . Study of gross anatomy and epithelial microstructure shows that mudskippers have not evolved novel musculature or glands to blink. Behavioral analyses show the blinks of mudskippers are functionally convergent with those of tetrapods: P. barbarus blinks more often under high-evaporation conditions to wet the eye, a blink reflex protects the eye from physical insult, and a single blink can fully clean the cornea of particulates. Thus, eye retraction in concert with a passive occlusal membrane can achieve functions associated with life on land. Osteological correlates of eye retraction are present in the earliest limbed vertebrates, suggesting blinking capability. In both mudskippers and tetrapods, therefore, the origin of this multifunctional innovation is likely explained by selection for increasingly terrestrial lifestyles.
2022
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Kinetics-informed neural networksGabriel S. Gusmão, Adhika P. Retnanto, Shashwati C. Da Cunha, and Andrew J. MedfordCatalysis Today, Apr 2022Chemical kinetics and reaction engineering consists of the phenomenological framework for the disentanglement of reaction mechanisms, optimization of reaction performance and the rational design of chemical processes. Here, we utilize feed-forward artificial neural networks as basis functions to solve ordinary differential equations (ODEs) constrained by differential algebraic equations (DAEs) that describe microkinetic models (MKMs). We present an algebraic framework for the mathematical description and classification of reaction networks, types of elementary reaction, and chemical species. Under this framework, we demonstrate that the simultaneous training of neural nets and kinetic model parameters in a regularized multi-objective optimization setting leads to the solution of the inverse problem through the estimation of kinetic parameters from synthetic experimental data. We analyze a set of scenarios to establish the extent to which kinetic parameters can be retrieved from transient kinetic data, and assess the robustness of the methodology with respect to statistical noise. This approach to inverse kinetic ODEs can assist in the elucidation of reaction mechanisms based on transient data.
