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Van 't Hoff Institute for Molecular Sciences Van 't Hoff Institute for Molecular Sciences

How a single monolayer can have a big impact on catalysis

21 December 2023

In a recent article published in ChemCatChem, researchers at the Heterogeneous Catalysis and Sustainable Chemistry group of the Van ‘t Hoff Institute for Molecular Sciences describe a way to optimize the electrochemical synthesis of glycine. They deposited a single atomic monolayer of lead on a copper electrode, which significantly inhibited the parasitic hydrogen evolution reaction. Such small modifications to an electrocatalyst can thus have a big impact on catalytic performance. The paper also shows that development of the catalyst in operando causes the formation of microparticles. These are likely to be the active catalytic species.
Graphical abstract of the paper. Image: HIMS / ChemCatChem.

Abstract of the paper

In the field of reductive organic electrosynthesis, the hydrogen evolution reaction (HER) is considered a parasitic reaction that lowers the Faradaic efficiency of the synthesis. Metals with a high overpotential for HER are often used to prevent this. However, this limits the catalytic materials that can be used in these reactions. To expand upon the scope of available electrocatalysts, we prepared a CuPb electrode via underpotential deposition (UPD). We thereby created an electrocatalyst with a single monolayer of Pb, CuPb1ML, in which Pb weight loading is only 415 ng cm-2, yet its properties could still effectively inhibit HER. The CuPb1ML electrode was used in the electrosynthesis of glycine from oxalic acid and hydroxylamine. This reaction served as a model for a C–N bond forming reaction in acidic aqueous media. The CuPb1ML electrode was compared against a pure Pb and Cu metal electrode. The CuPb1ML electrode showed a Faradaic efficiency for glycine production of 57%, which was 9-fold higher than Cu and rivaled the Pb electrode. The catalytic activity of CuPb1ML was 211 µmol h-1 cm-2, which is higher than both Cu and Pb. The mechanism of the electroreduction was then studied via in situ Fourier Transform Infra-Red (FTIR) spectroscopy. These results hinted to an evolution of the electrocatalyst during the electrolysis reaction, which was then studied via Scanning Electron Microscopy (SEM) and X-Ray Photoelectron spectroscopy (XPS). We found that the Pb monolayer restructured during catalysis, forming microparticles that were active in the reaction based on the listed experiments. Pb alloying into the lattice, which can occur during UPD, also lowered the HER, further facilitating glycine synthesis. Thus, our research also shows how Pb UPD impacts the catalytic properties of a metal both through monolayer deposition as well as surface alloying.

Paper details

Pim Broersen, Thijs de Groot, Didjay Bruggeman, Emma Caarls, Jamie Trindell, Dimitra Anastasiadou, Marta Figueiredo, Gadi Rothenberg, Amanda C. Garcia, Enhancing Electrocatalytic Synthesis of Glycine with CuPb1ML Electrode Synthesized via Pb UPD. ChemCatChem 2023, e202301370. DOI: 10.1002/cctc.202301370

See also

Research group Heterogeneous Catalysis and Sustainable Chemistry