Inexpensive Amorphous FeIII Oxo‐/Hydroxide as Highly Active and Ultradurable Electrocatalyst for Water Electrolysis

Abstract

AbstractDeveloping highly active, cost‐effective, and robust electrocatalysts for the oxygen evolution reaction (OER) still remains a crucial challenge for enhancing the conversion of sustainable energy resources. The performances of existing electrocatalysts is restricted by low electronic conductivity and the limited amount of active sites. Herein, newly synthesized FeIIIOH nanoparticles (NPs) are shown to be efficient and durable electrocatalysts for the OER reaction. FeIIIOH NP‐coated nickel foam (FeIIIOH NPs/NF) operates at an overpotential of 300 mV (@10 mA cm−2) with excellent stability even after 30 h and shows higher stability relative to a cell voltage of 1.55 V in alkaline media, which is substantially lower than the commercial electrocatalyst IrO2 (1.61 V). The FeIIIOH NPs/NF overpotential of 300 mV at 10 mA cm−2 is 89 and 127 mV lower than IrO2/NF (389 mV) and NF (427 mV), respectively. The Tafel slope of FeIIIOH NPs/NF (104 mV dec−1) is lower than IrO2/NF (164 mV dec−1) and NF (199 mV dec−1). The calculated turnover frequency (TOF) of FeIIIOH NPs (0.0128 s−1) is approximately five times higher than that of the IrO2 catalyst (0.0089 s−1) at 1.60 V. This reflects that the FeIIIOH NP catalyst is intrinsically active, giving outstanding OER performances and showing satisfactory kinetics to overcome the sluggish water oxidation rate. Solar water electrolysis shows continuous evolution of oxygen and hydrogen gas at the anode and cathode, respectively, at 1.55 V. The amount of hydrogen generated during solar water electrolysis was calculated as 3.22 mmol h−1 cm−2, which is close to the coulombic efficiency at 1.55 V. This demonstration develops the hope for superior exploration of FeIIIOH NPs/NF toward the expansion of real and large‐scale hydrogen production with the lowest price.