The catalytic system was developed by PhD candidate Pim Broersen under supervision of Dr Garcia and in collaboration with Chemistry Master's student Joost Koning and Prof. Gadi Rothenberg. It employs the well-known alcohol oxidation catalyst/redox mediator 2,2,6,6-tetramethylpiperidinyloxyl, a radical species that is more commonly known as TEMPO.

By using a polymer-based electrode that fixes TEMPO on a solid support, the researchers were able to realize selective electrooxidation of methanol to formaldehyde with up to 97.5% Faradaic efficiency and turnover numbers up to 17100. Combined with the elimination of the platinum group metals, the method paves the way for more sustainable industrial processes. The research also demonstrates the electrocatalyst's capability to oxidize various aliphatic alcohols, highlighting its broad applicability.

Abstract, as published in the paper

In the chemical industry, formaldehyde is an important bulk chemical. The traditional synthesis of formaldehyde involves an energy intensive oxidation of methanol over a metal oxide catalyst. The selective electrochemical oxidation of methanol is challenging. Herein, we report a catalytic system with an immobilized TEMPO electrode that selectively oxidizes methanol to formaldehyde with high turnover numbers. Upon the addition of various organic and inorganic bases, the activity of the catalyst could be tuned. The highest Faradaic efficiency that was achieved was 97.5 %, the highest turnover number was 17100. Additionally, we found that the rate determining step changed from the step in which the carbonyl specie is created from the methanol-TEMPO adduct to the oxidative regeneration of the TEMPO⁺ species. Finally, we showed that the system could be applied to the oxidation of other aliphatic alcohols.

Paper details

P. J. L. Broersen, J. J. N. Koning, G. Rothenberg, A. C. Garcia: A Highly Efficient Electrosynthesis of Formaldehyde Using a TEMPO-Based Polymer Electrocatalyst. Chemistry Europe, First published: 02 July 2024. DOI: https://doi.org/10.1002/cssc.202400582

See also

Research group Heterogeneous Catalysis and Sustainable Chemistry