Monodisperse Os-O-Co Modules Enable Ampere-Level Hydrazine-Assisted Seawater Splitting in Membraneless Electrolyzers

Abstract

Hydrazine oxidation-assisted seawater electrolysis (HzOR-SWE) is critical for addressing freshwater scarcity and energy crises. However, the development of this technology has been significantly impeded by the absence of efficient catalysts capable of cleaving N─H bonds during the hydrazine oxidation reaction (HzOR). Herein, Monodispersed Os-O-Co modules are constructed within a cobalt hydroxide structure via an in situ osmium (Os) single-atom modification strategy to serve as a bifunctional catalyst. The d-p orbital hybridization in the structure shifts the d-band center of Os sites away from the Fermi level, weakening the adsorption energy of reaction intermediates and exhibiting the lowest N─H dehydrogenation energy barrier for HzOR and moderate active hydrogen adsorption energy for hydrogen evolution reaction (HER). When integrated into a membraneless flow cell (MFC), the catalyst demonstrates exceptional performance in HzOR-SWE, requiring only 0.768 V to deliver 1.0 A cm⁻² with a remarkable rate of 31.9 moles of hydrogen per kilowatt-hour (kWh). This represents a 70.7% energy saving compared to conventional seawater splitting systems (2.62 V, 7.6 kWh mol⁻¹). This work holds significant importance for advancing the economic viability of low-energy seawater electrolysis for hydrogen production.