Membrane-free sequential paired electrosynthesis of 1,4-hydroquinone from phenol over a self-supported electrocatalytic electrode

Sequential paired electrosynthesis capable of the production of organic chemicals through a series of electrochemical reactions that occur consecutively and in pairs are of high significance. Herein, a three-dimensional porous carbon felt-loaded PbO₂ electrode (PbO₂/CF) with a self-supported nanostructure was fabricated using a double-cathode electrodeposition method, which served as an efficient electrocatalyst enabling the unique sequential paired electrosynthesis of 1,4-hydroquinone (1,4-HQ) from phenol in a membrane-free electrolytic cell. In such an exotic paired electrolysis system, phenol is first oxidized to p-benzoquinone at the anode, which is subsequently reduced to 1,4-HQ at the cathode. The as-obtained PbO₂/CF electrode exhibited a remarkable electrochemical performance, achieving impressive conversion and selectivity of 94.5% and 72.1%, respectively, for the conversion of phenol to 1,4-HQ. This exceptional performance can be attributed to the open porous self-supported structure of the PbO₂/CF electrode, which improves the active site exposure and substrate adsorption capability and reduces mass and charge transfer resistance. Furthermore, the catalyst electrode well maintained its structure integrity even after 140 hours of long-term use, further highlighting its promising application for the electrosynthesis of 1,4-HQ. Moreover, this sequential paired electrosynthesis strategy can be further extended to other substrates with electron-withdrawing/donating groups over the PbO₂/CF electrode. The proof of concept in this innovative sequential paired electrosynthesis could provide a sustainable and efficient way to produce various desired organic compounds.