Rapid electrodeposition synthesis of partially phosphorylated cobalt iron phosphate for application in seawater overall electrolysis

To obtain hydrogen energy from seawater, it is of utmost importance to design an efficient bifunctional electrocatalyst that can be produced on a large scale and in a rapid manner. In this work, iron cobalt phosphate (CoFe-EP/NF) for long-term efficient and stable seawater electrolysis were rapidly synthesized by a simple electrodeposition. The study showed that metal phosphides/phosphates provided additional active sites for the catalysts for hydrogen evolution reaction (HER, 160 mV at 100 mA/cm(2)) and oxygen evolution reaction (OER, 266 mV at 100 mA/cm(2)), in alkaline seawater electrolyte (1 M KOH + seawater), respectively. Notably, the presence of phosphate groups facilitates the transformation of cobalt-iron metal phosphates into the truly reactive substance CoOOH, which improves the OER kinetics. In addition, the phosphate layer formed after catalyst activation avoids the occurrence of chlorine evolution reaction (CER) by shielding the adsorption of Cl-, thus enhancing the corrosion resistance and enabling long-term stable operation in seawater. The two-electrode overall seawater electrolysis easily reaches 100 mA/cm(2) at 1.68 V and exhibit a long-term durability of more than 100 h. This study offers a viable approach for the synthesis of electrocatalysts with high activity and corrosion resistance, which is vital for the practical realization of large-scale seawater electrolysis.