Electrocatalytic Selective Oxygen Evolution of Carbon-Coated Na₂Co_1-xFe_xP₂O₇ Nanoparticles for Alkaline Seawater Electrolysis

For mass production of hydrogen fuel by electrochemical water splitting, seawater electrolysis is preferred over freshwater electrolysis because of the abundance of seawater in nature. However, the electrochemically active anions in seawater can cause the corrosion of electrodes or undesirable side reactions during the anodic reaction at the anode, thus degrading the overall system efficiency. Hence, it is imperative to develop highly active and stable oxygen evolution reaction (OER) electrocatalysts for efficient seawater electrolysis. In this study, carbon-coated sodium cobalt-iron pyrophosphate (Na₂Co_1-xFe_xP₂O₇/C, 0 ≤ x ≤ 1) nanoparticles (NCFPO/C NPs) and NCFPO/C NPs loaded on a carbon cloth (NCFPO/C@CC) are fabricated as a promising OER electrocatalyst for alkaline seawater electrolysis. The electrocatalytic OER performance of the NCFPO/C NPs is optimized by controlling their Co/Fe ratio. NCFPO/C@CC acts as an efficient OER electrocatalyst during the OER test in an alkaline saline solution without corroding the electrode and generating reactive chloride species. It also exhibits long-Term stability and durability with continuous oxygen generation. In addition, NCFPO/C@CC shows the electrocatalytic OER activity in alkaline seawater, demonstrating that NCFPO/C is a promising candidate as an OER electrocatalyst for realistic alkaline seawater electrolysis.