Inspiring Plenary Lectures by International Experts

The interplay between the electrode surface, water, and ions at the electrode-electrolyte interface is a key factor in the performance of electrolyzers. Here, I will discuss our efforts to understand this interfacial chemistry using X-ray spectroscopy. To this end, we have designed operando X-ray photoelectron spectroscopy and (soft) X-ray absorption spectroscopy methodology that can specifically detect the individual chemistries of interfacial water, near-surface ions, and the electrode surface. Here, I will discuss case studies from both alkaline and acidic electrolysis, in which we investigated electrolyte effects and electrode restructuring. 

Formation of intermediates and degradation products, ion transport and crossover of active species through membranes are all important processes synergistically affect the performance of a redox flow battery. I will present how we couple nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) to probe these processes in operando. NMR and EPR are non-invasive, atom-specific, quantitative and complementary to one another – the former detecting diamagnetic species and the latter paramagnetic species. Using anthraquinone and viologen-based RFBs as examples, I will demonstrate the detection and quantification of radical intermediates and degradation products. I will show how the electronic structures of the radicals can be revealed through the analysis of the hyperfine coupling features of the EPR spectra. Furthermore, lithium ion transport through the membranes, as a function of charge-discharge cycles, can be captured and quantified, as well as the crossover of the redox-active species. Simultaneously, I will demonstrate that compact and low-cost benchtop NMR and EPR systems have sufficient spectroscopic resolution and sensitivity to perform these mechanistic studies, with the hope of increasing the accessibility to a broader electrochemistry community.         

Electrolysis is at the core of Power-to-X (P2X) technologies, enabling the conversion of renewable electricity into fuels and chemicals. Among electrolysis technologies, Solid Oxide Electrolysis Cells (SOECs) and Proton-Conducting Electrolysis Cells (PCECs) stand out for their high efficiency, benefiting from favorable thermodynamics and reaction kinetics at elevated temperatures. A key advantage of these technologies is their reliance on scalable, non-precious materials such as nickel, zirconia, and steel, making them cost-competitive. While SOECs are relatively mature and widely used for the co-electrolysis of CO₂ and H₂O to produce syngas (CO and H₂), PCECs offer a unique advantage by operating at lower temperatures, facilitating the direct production of methane (CH₄), higher hydrocarbons (C₂, C₃), and alcohols. These emerging technologies hold significant potential for enabling carbon-neutral energy cycles and expanding P2X applications. 

Despite their promise, SOECs and PCECs face critical degradation challenges that hinder commercialization. SOEC degradation primarily occurs at the stack level, requiring improvements in interconnect coatings, contact materials, and thermal stability. PCECs, still in an earlier stage of development, suffer from single-cell degradation issues, including electrode sintering, proton transport limitations, and chemical instability under CO₂/H₂O electrolysis conditions. In this contribution, we will explore advancements in materials, novel cell architectures, and innovative operation modes—such as coupling with thermal catalysis and plasma activation—aimed at enhancing SOEC and PCEC performance and accelerating their commercial viability. 

This lecture delves into the fundamental principles underlying the electrochemical reduction of carbon dioxide (CO2RR) and its interaction with the hydrogen evolution reaction (HER). Our focus is on our group’s extensive exploration of CO2RR on copper electrodes in organic solvents. 

Utilizing online gas chromatography and in situ FTIR spectroscopy, our findings underscore the significant impact of electrode morphology and solvent composition on this reaction. Notably, in solvents such as acetonitrile, our analyses reveal the critical role of water content at the solid-liquid interface in determining reaction selectivity. We also demonstrate that the CO2 reduction reaction competes with HER under these conditions. 

Building on prior observations in aqueous solvents, our study elucidates the decisive influence of alkyl cation length—commonly used as an electrolyte in organic solvents—on the reaction mechanism. Specifically, our data show that smaller cations (TEA) promote the formation of oxalic acid, while larger cations (TBA) favor the production of carbon monoxide. 

Moreover, we investigated the impact of amine solvents on carbon capture and utilization in a direct process. Our in situ spectroscopic analysis indicates that the steric effects of amines and their interactions with the electrode surface significantly influence product distribution during CO2RR. 

This lecture will leverage advanced in situ spectroscopic techniques and DFT calculations to elucidate the complex mechanisms behind these reactions and highlight the pivotal role of the cation in determining product distribution. 

Alexander Bagger  Technical University of Denmark, Department of Physics

I will discuss how experiments and computational simulations can support each other. I will focus on electrochemical reduction of NOx, CO2, N2, and the combinations. Importantly, all these reactions share a direct competition with hydrogen, and furthermore, several products are formed from each reactant of these reactants. I will give minimalistic models that do not overfit or over interpretating experimental data: 

1. eCO2 reduction show multiple different products depending on metal catalyst1,2 
2. eNOx reduction produce N2O, N2 and NH33,4. Interestingly, reactive metals work close to their reduction potential5-6. 
3. eN2 reduction to NH3 at ambient conditions has been confirmed on a Li-mediate system7. I will discuss systems beyond lithium8. 
4. Finally, I will show predictive schemes for the synthesis of urea9,10. 

[1] Hori et. al., J. Chem. Soc., Faraday Trans., 1989. 
[2] Bagger et. al., ChemPhysChem, 2017.
[3] Rosca, Duca, Groot, Koper, Chem. Rev. 2009.
[4] Wan, Bagger, Rossmeisl, Angew. Chem., 2021.
[5] Carvalho, …, Stoerzinger, JACS 2022.
[6] Riyaz, Bagger, Electrochim. Acta. 2025.
[7] Tsuneto et al. JEAC. 1994.
[8] Bagger, et. al., ACS Energy Letters. 2024.
[9] Wan, …, Bagger, ACS Catalysis, 2023.
[10] Wuttke, Bagger, Commun. Chem. 2025. 

Integrating the electrooxidation of an organic compound, such as an alcohol, in a water electrolyzer is a promising strategy for saving energy during hydrogen production while forming value-added products at the anode. This approach is known as hybrid water electrolysis (HWE). In this contribution, the concept of “energy saving” in HWE is illustrated by comparing the performance of a series of LaFe1xCoxO3 perovskites towards the oxygen evolution, and the electrooxidation of glycerol and isopropanol.[1] As a second example, the influence of various operating conditions, including electrode potential and electrolyte composition, on the performance of Ni oxide nanoparticles towards the electrooxidation of glycerol is discussed.[2] The results shown here illustrate the trade-off between activity and selectivity in HWE, and highlight the need for identifying suitable catalysts and electrolysis conditions to minimize this trade-off.[3] 

References: [1] A.C. Brix, et al. ChemElectroChem 9 (2021) e202200092 [2] D.M. Morales, et al. ACS Catalysis 12 (2022) 982-992 [3] F.J.A. van Lieshout & D.M. Morales, ChemPlusChem 89 (2024) e202400182.