The demand for sustainable and environmentally friendly processes of producing syngas has led to the development of high-temperature co-electrolysis of carbon dioxide and steam. In an electrolyser, molecular hydrogen and oxygen are produced by water, respectively at the cathodic and anodic side, thanks to an external electrical power supply. In the same way, CO2 can be converted into CO and oxygen in a reaction named carbon dioxide electrolysis. CO2 and H2O electrolysis can be paired together (co-electrolysis) to obtain H2 and CO, which is known as syngas, a widely used intermediate gas mixture in synthesis processes. Performing the process at high rather than low temperatures has the advantage of requiring less electrical energy. This is explained by the decrease of the ?G of the reactions with increasing temperature1. Therefore, solid oxide electrolyser cells (SOECs) are currently at the cutting edge of research. Since the output syngas ratio is a key factor, it is crucial to understand the effects related to the functioning of the electrolyser. These can be estimated through a model, aiming at evaluating the current-voltage (j-V) SOEC curves and the composition of the syngas produced in different operating conditions. In this framework, a zero- dimensional model is developed. The chemical part of the model includes the calculation of the outlet cathode gas composition, considering that the water gas shift reaction occurs and reaches thermodynamic equilibrium: CO+H2O?<-? CO2+H2 (1) The electrochemical part of the model is based on the calculation of the Nernst reversible voltage UN. Then, the operating voltage U is obtained by subtracting all the voltage losses, which include ohmic, concentration and activation losses: U=UN+?ohm +?conc +?act (2) The theoretical equations have been implemented in Matlab. The simulation results show that the CO2:H2O ratio in the cathode inlet gas strongly influences the slope of the j-V curves. This work is developed with the fundings of the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.3 - Call for tender No. 1561 of 11.10.2022 of Ministero dell'Università e della Ricerca (MUR); funded by the European Union - NextGenerationEU- : Project code PE0000021, Concession Decree No. 1561 of 11.10.2022 adopted by Ministero dell'Università e della Ricerca (MUR), CUP - D33C22001330002, Project title "Network 4 Energy Sustainable Transition - NEST".

Zero-dimensional model for a planar Solid Oxide Electrolyser Cell (SOEC) at different working temperatures

M Viviani;S Presto;
2023

Abstract

The demand for sustainable and environmentally friendly processes of producing syngas has led to the development of high-temperature co-electrolysis of carbon dioxide and steam. In an electrolyser, molecular hydrogen and oxygen are produced by water, respectively at the cathodic and anodic side, thanks to an external electrical power supply. In the same way, CO2 can be converted into CO and oxygen in a reaction named carbon dioxide electrolysis. CO2 and H2O electrolysis can be paired together (co-electrolysis) to obtain H2 and CO, which is known as syngas, a widely used intermediate gas mixture in synthesis processes. Performing the process at high rather than low temperatures has the advantage of requiring less electrical energy. This is explained by the decrease of the ?G of the reactions with increasing temperature1. Therefore, solid oxide electrolyser cells (SOECs) are currently at the cutting edge of research. Since the output syngas ratio is a key factor, it is crucial to understand the effects related to the functioning of the electrolyser. These can be estimated through a model, aiming at evaluating the current-voltage (j-V) SOEC curves and the composition of the syngas produced in different operating conditions. In this framework, a zero- dimensional model is developed. The chemical part of the model includes the calculation of the outlet cathode gas composition, considering that the water gas shift reaction occurs and reaches thermodynamic equilibrium: CO+H2O?<-? CO2+H2 (1) The electrochemical part of the model is based on the calculation of the Nernst reversible voltage UN. Then, the operating voltage U is obtained by subtracting all the voltage losses, which include ohmic, concentration and activation losses: U=UN+?ohm +?conc +?act (2) The theoretical equations have been implemented in Matlab. The simulation results show that the CO2:H2O ratio in the cathode inlet gas strongly influences the slope of the j-V curves. This work is developed with the fundings of the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.3 - Call for tender No. 1561 of 11.10.2022 of Ministero dell'Università e della Ricerca (MUR); funded by the European Union - NextGenerationEU- : Project code PE0000021, Concession Decree No. 1561 of 11.10.2022 adopted by Ministero dell'Università e della Ricerca (MUR), CUP - D33C22001330002, Project title "Network 4 Energy Sustainable Transition - NEST".
2023
Istituto di Chimica della Materia Condensata e di Tecnologie per l'Energia - ICMATE
9788875902704
SOEC
Electrolysis
Modeling
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/461923
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