Sacrificial Fe sites making 2D heterostructure an efficient catalyst for oxygen evolution reaction in alkaline seawater†

Abstract

Hydrogen via direct seawater splitting is a viable option, but anodic oxygen evolution reaction (OER) faces challenges when seawater is used, and to realize seawater splitting at full potential, efficient and effective catalysts are needed. Here, we introduced a unique two-dimensional molybdenum oxide@iron oxide (MO@FO) heterostructure synthesized via a simple hydrothermal process for anodic OER in alkaline seawater. Chemically bonded two dissimilar oxides create a unique platform that only requires 1.52 and 1.72 V to achieve current densities of 100 and 500 mA cm⁻², respectively, in alkaline seawater. MO@FO displayed anti-corrosive behavior as it possesses a low corrosion current of 9 nA cm⁻² and a corrosion rate of only 0.036 μm per year. It inhibits chlorine evolution reaction and hypochlorite generation, confirmed by GC-MS and DPD tests, hence remained stable for over 1000 h. The DFT calculations show that MoO₂ is the active centers in the heterostructure while addition of polyanions assists in the formation of a protective layer on the catalyst surface, providing additional protection against chloride ions. Hence, this study presents an effective and efficient strategy for stable anodic reactions in alkaline seawater for hydrogen production.