Cobalt–Iron Co-substituted NiV Layered Double Hydroxide as a High-Performance Electrocatalyst for Oxygen Evolution Reaction in a Neutral Saline Medium

Abstract

For practically viable electrochemical water splitting at a large scale, it is imperative to develop highly efficient electrocatalysts that work well in neutral electrolytes. However, the kinetics of the OER is retarded in neutral pH electrolytes, resulting in scarce highperformance neutral OER electrocatalysts. In the present study, the sluggish kinetics of neutral OER is overcome by substituting Co 2+ and Fe 2+ cations in the place of Ni 2+ ions in NiV layered double hydroxide (LDH), which act as adsorption sites for hydroxyl anion for promoting the OER process in neutral saline electrolytes for the first time. CoFe co-substituted NiV contains partially reduced metallic Co and Fe species and a hybrid morphology, which helps in driving the neutral OER as verified by electrochemical studies. The DFT first principle studies revealed that the cation co-doping leads to the localization of d-band electrons in NiV LDH, resulting in improved conductivity and more active sites. CoFe-NiV shows a low overpotential of 150 mV at 10 mA/cm 2 , the least among other reported LDH-based catalysts for neutral OER, to the best of our knowledge. The co-substituted catalyst showed a Tafel slope of 136 mV/dec and delivered a stable current of 10 mA/cm 2 for 12 h.

Breaking the Scaling Relationship of Oxygen Evolution Reaction and Chlorine Oxidation Reaction via MnO2 Polymorphic Engineering for Selective Seawater Electrolysis

“…Furthermore, a low value of the Tafel slope at a lower overpotential range indicates the involvement of the Langmuir–Hinshelwood (LH) mechanism, where the active sites are covered by a combination of oxide and hydroxyl . On the other hand, the high value of Tafel slope in a higher overpotential region is because of additional resistance provided to OH – ions by accumulated unoxidizable ClO 4 – ions near the anode region . Moreover, as the overpotential increases, the reaction mechanism shifts to the Eley–Rideal (ER) mechanism, in which the active sites are covered with oxygen species and lead to a higher Tafel slope .…”