FeOOH-containing hydrated layered iron vanadate electrocatalyst for superior oxygen evolution reaction and efficient water splitting

A new FeOOH-containing Fe5V15O39(OH)9·9H2O (FVO) has been shown to exhibit superior oxygen evolution reaction (OER) and efficient overall water splitting activities. The critical FeOOH, whose formation is controlled by the surface oxidation state and oxygen vacancy, dominates to improve the OER activity. The co-existence of γ-FeOOH, γ-VOOH, metallic Fe after activation enhances the OER activity. Oxygen vacancy and crystal water have also been shown to enhance the charge transfer. The optimized electrocatalyst gives OER current densities of 10 and 1000 mA cm−2 at excellent overpotentials of 195 and 293 mV, respectively. The electrocatalyst also shows excellent bifunctional performance for full-cell water splitting in alkaline electrolyte, giving a large current density of 1000 mA cm−2 at 2 V and is stable for 85 h. This work provides a new avenue to design an efficient and stable electrocatalyst material with large current density.