Electrocatalytic hydrogenation processes (ECH) allow the sustainable direct conversion of organic substances using electric current on a catalytically active electrode without the necessity of hydrogen gas, elevated temperatures, or pressures. In a previous project, our group developed a zero-gap electrolyzer that allowed Faraday efficiencies (FE) of 75% for the semi-hydrogenation of 2-methyl-3-butyne-2-ol (MBY) to the Vitamin E-synthon 2-methyl-3-butene-2-ol (MBE) at current densities and run times significantly surpassing those of established protocols.^[1]

Herein, we illustrate the electrochemical deposition of silver, copper and nickel on different carbon carrier materials on a time scale of 5 – 15 min per electrode in an electrochemical flow cell. Depending on the applied current density, the time of deposition and the flow rate of the metal electrolyte, entirely different morphologies, sizes and crystallinities of the metal particles were obtained featuring characteristic current efficiencies in the ECH of MBY. Among other things, this makes the configuration of this work stand out against state-of-the-art systems, in which electrode preparation is mostly carried out upon application of specifically prepared catalyst inks on a carrier material e.g. by spray coating or drop-casting, which means a significant additional time and resource expense for the whole process. Since the electrodes were applied in a zero-gap flow reactor similar to the flow cell that was used for electrode preparation, the presented electrode configuration allows the preparation and use of the materials in one process step without intermediate processing or purification.

The prepared silver-plated air-stable carbon electrodes enable the ECH of MBY at 93% current efficiency at 80 mA cm^-2. The concept features extraordinary resource efficiency, resistance towards errors in preparation and an outstanding performance of 76% FE and a cell voltage of 2.7 V at 240 mA cm^-2 current density and a loading of 0.2 mg cm^‑2, corresponding to a production rate of 1465 g_MBE g_cat^-1 h^-1. These numbers are reproducible even upon single-pass operation which is widely applied in industrial protocols. With this, it surpasses the performance of state-of-the-art electrocatalytic systems^[1,2] for MBE-generation and even approaches that of the best reported thermocatalytic ones.^[3]

Remarkably, the electrode concept is applicable to a range of 17 C-C‑, C-O- and N-O-unsaturated compounds among which seven could be converted with a current efficiency >45% with MBY, benzaldehyde, 2-butynol and nitromethane even allowing their hydrogenation in neat form without the addition of solvent or electrolyte salts.

This work provides a valuable contribution to the transfer of electrocatalytic hydrogenation processes onto an industrially relevant platform and addresses the room for improvement of established processes from a wide point of view by considering the whole electrode life cycle.