Cutting the overpotential of electrochemical hydrogenations for enhanced hydrogenation efficiency

Abstract

Electrochemical hydrogenations (ECH) of biogenic platform molecules offer a sustainable alternative to catalytic hydrogenations, but their efficiency is often limited by high overpotentials and competition with the hydrogen evolution reaction (HER). In this study, we demonstrate that hydrogenations of levulinic acid and furfural can be carried out efficiently at electrode potentials positive to the reversible hydrogen electrode (RHE) and close to the thermodynamic standard potential of the respective redox processes, thereby overcoming a central barrier to the energetic feasibility of ECH. Using platinized platinum electrodes, we exploit the hydrogen underpotential deposition (H_upd) region, where adsorbed hydrogen monolayers form, to catalyse reductive transformations under mild conditions. Electrolysis experiments reveal that hydrogenation commences already in the H_upd region, achieving Coulomb efficiencies up to 76% for levulinic acid and 53% for furfural hydrogenation at +0.015 V vs. RHE—among the highest values reported at low substrate concentrations. These findings establish the H_upd region as a previously overlooked window for efficient electrochemical hydrogenations, highlighting a promising strategy to reduce energy demand, suppress HER, and advance the integration of biogenic feedstocks into electrochemical valorisation processes.