Energy-Saving Electrochemical Hydrogen Production Coupled with Biomass-Derived Isobutanol Upgrading.

Abstract

The widespread application of electrochemical hydrogen production faces significant challenges, primarily attributed to the high overpotential of the oxygen evolution reaction (OER) in conventional water electrolysis. To address this issue, an effective strategy involves substituting OER with the value-added oxidation of biomass feedstock, reducing the energy requirements for electrochemical hydrogen production while simultaneously upgrading the biomass. Herein, we introduce an electrocatalytic approach for the value-added oxidation of isobutanol, a high energy density bio-fuel, coupled with hydrogen production. This approach offers a sustainable route to produce the valuable fine chemical isobutyric acid under mild condition. The electrodeposited Ni(OH)2 electrocatalyst exhibits exceptional electrocatalytic activity and durability for the electro-oxidation of isobutanol, achieving an impressive faradaic efficiency of up to 92.4 % for isobutyric acid at 1.45 V vs. RHE. Mechanistic insights reveal that side reactions predominantly stem from the oxidative C-C cleavage of isobutyraldehyde intermediate, forming by-products including formic acid and acetone. Furthermore, we demonstrate the electro-oxidation of isobutanol coupled with hydrogen production in a two-electrode undivided cell, notably reducing the electrolysis voltage by approximately 180 mV at 40 mA cm-2. Overall, this work represents a significant step towards improving the cost-effectiveness of hydrogen production and advancing the conversion of bio-fuels.