Carbon-based materials for sustainable electrochemical hydrogenations
Year: 2026
Type: dissertation
Abstract: The chemical manufacturing sector is one of the most important industries of modern society. However, the processes currently employed for chemical production impact the environment considerably, accounting for a significant part of greenhouse gas emissions and energy consumption. Hydrogenations are a paramount class of reactions for the production of plastics, pharmaceuticals and food, but they require elevated temperatures, pressurized hydrogen and (noble) metal catalysts. In our continuous effort to decarbonize industrial activity, electrochemistry rises as a sustainable alternative to carry out these reactions, under ambient conditions. Nonetheless, most electrochemical processes still rely on (noble) metals and/or (per)fluorinated binder materials, thus posing sustainability limitations on their widespread employment. This dissertation aims to employ carbon-based materials as sustainable alternatives for electrochemical hydrogenations (ECHs) and assess their structure-performance relationship. The materials are also benchmarked against counterparts, either commercial, or found in literature, to elucidate their influence on the reaction and evaluate their performance. Chapter 2 focuses on the use of N-doped carbons as hydrogenation electrocatalysts. By utilizing a salt-melt templated synthesis, nanoporous N-doped carbons are produced and employed for the electrochemical hydrogenation of maleic to succinic acid, the latter being a valuable commodity chemical. Mechanistic investigations indicate that N-doping induces specific electrode-organics adsorptive interactions, and the hydrogenation proceeds with a mechanism resembling that of metals. Additionally, the obtained yields are compared to other heterogeneous catalytic processes that utilize metals for maleic acid hydrogenation, showing that electrochemical hydrogenations can be conducted in ambient and metal-free conditions, without compromising the yield of the reaction. In Chapter 3 non-noble metal Single Atom Catalysts (SACs) were synthesized, bearing Fe, Ni, or Co atoms, anchored on a N-doped carbon shell. The SACs were utilized for the semi-ECH of alkyne(di)ols to alkene(di)ols, exhibiting high chemoselectivity over the competing full hydrogenation to alkane(di)ols. Moreover, they exhibited distinct stereoselectivities depending on the metal, allowing for the tunable synthesis of cis- or trans-alkenediols. Finally, the SACs were compared to their nanoparticle counterparts, which did not exhibit any metal-dependent stereoselectivity. This comparison indicates that the unique reactivities discussed stem from both the metal active sites and their atomic coordination. Chapter 4 examines the use of poly(ionic liquids) (PILs) as binders for ECH. The PIL bound electrodes outperformed electrodes using commercial fluorinated binders for the ECH of benzaldehyde to benzyl alcohol. This performance enhancement was investigated by mechanistic studies, as well as in-situ local pH electrochemical measurements. It is shown that the PIL binders’ structure and charge massively influence the electrode’s microenvironment during polarization, due to electrostatic and chemical effects. These factors enhance both the yield and Faradaic efficiency of the reaction. Finally, the versatility of PILs enhancement is assessed for further ECH reactions, over a broad range of more than 12 pH units.
Author: Grammenos, Anastasios Orestis
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7139933839
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