Sustainable Hydrogen Generation Facilitated through Ethylene Glycol Oxidation in Fresh/Seawater with Cobalt- and Iron-Based Fluorinated Nanosheets

Abstract

Replacing the kinetically sluggish and energy-intensive oxygen evolution reaction (OER) at the anode with the oxidation of more kinetically and thermodynamically favorable small organic molecules is a promising strategy for boosting hydrogen production. This study focuses on sustainable hydrogen generation at the cathode facilitated by the ethylene glycol oxidation reaction (EGOR) at the anode, coupled with the production of value-added formate. For this, we designed and deposited cobalt- and iron-based fluorinated two-dimensional (2D)-nanosheets (2D-CoFe@OF) through a straightforward hydrothermal method onto a nickel foam substrate (NF). The resulting 2D-CoFe@OF/NF exhibits an anodic potential that is 100 mV lower in a 0.5 M EG-added 1.0 M KOH electrolyte to achieve a benchmark electrolysis current density of 10 mA cm^–2, compared to a pure 1.0 M KOH electrolyte. Additionally, assembling two identical 2D-CoFe@OF/NF||2D-CoFe@OF/NF electrode-based electrolyzers resulted in a 150 mV reduction in operating cell voltage when electrolyzing at 150 mA cm^–2, particularly when the OER was replaced by EGOR, thereby demonstrating a significant improvement in energy efficiency. Under this condition, the electrolyzer demonstrated a nearly 100% Faradaic current efficiency for the hydrogen evolution reaction (HER). Furthermore, the practical application of this system studied with an EG-seawater electrolyzer suggests its potential to replace freshwater with abundant seawater, thereby expanding the horizon for sustainable hydrogen generation. This study, thus, highlights the promising potential of the 2D-CoFe@OF nanosheets on EGOR in seawater, advancing green hydrogen technology toward a more sustainable future.