Efficient and selective seawater oxidation by manganese ferrite electrocatalysts obtained via a vapor phase strategy

Abstract

Electrolysis of seawater is an appealing route for the production of green hydrogen without any stress on drinkable freshwater reservoirs, but its large-scale exploitation is harshly limited by the anodic chlorine oxidation reaction (ClOR), resulting in material corrosion and limiting the efficiency and sustainability of this technology. Consequently, active, stable, and eco-friendly electrocatalysts capable of selectively promoting the oxygen evolution reaction (OER), suppressing thus ClOR, are highly demanded for further advancements in the field. In this context, the present work reports for the first time on the fabrication of crystalline manganese ferrite thin films by an original chemical vapor deposition (CVD) route, starting from a mixture of Mn and Fe β-diketonate diamine adducts acting as single-source precursor for the target systems. Controlled variations of the relative precursor amounts allowed to modulate the structural and compositional characteristics of the resulting materials, with particular regard to the Mn/Fe ratio. Electrochemical tests in real seawater environments yielded, for the best performing system, an outstanding Tafel slope of ≈60 mV dec⁻¹, and enabled to rule out hypochlorite generation. These performances, accompanied by an appreciable operational stability, underscore the potential of the present electrocatalysts for renewable energy-related applications.