A bifunctional electrocatalyst for energy-efficient hydrogen production and ethanol upgrading into acetate via hybrid seawater splitting

Abstract

The sluggish kinetics of the oxygen evolution reaction (OER) and the competing chlorine evolution reaction (CER) significantly limit the efficiency of seawater electrolysis for hydrogen production. Replacing OER/CER with thermodynamically more favorable anodic reactions presents a promising strategy for reducing energy consumption and overcoming chlorine-based toxic products. This study reports a hybrid seawater electrolysis system that couples the ethanol oxidation reaction (EOR) with the hydrogen evolution reaction (HER), enabling the co-production of green hydrogen and value-added potassium acetate in alkaline seawater. Utilizing bimetallic NiCu hierarchical nanostructures supported on nickel foam (NiCu–HNS@NF) as a bifunctional electrocatalyst, this promising system required 220 mV less potential for EOR compared to OER to achieve a current density of 20 mA cm⁻². Meanwhile, the HER required a low overpotential of only 97 mV to attain the same current density, with a faradaic efficiency (FE) of 97.6%. The CO₂-free selective conversion of ethanol into acetate, along with the high faradaic efficiency (FE) for H₂, may be attributed to the bubbles-templated interconnected hierarchical nanostructures and the bimetallic synergistic effect. This study highlights the potential of ethanol-assisted seawater electrolysis as an energy-efficient and economically viable platform for sustainable hydrogen production and biomass valorization.