Cobalt-Doped Nickel-Based MXene with Fluorinated Terminal Groups (Co−Ni3C−F) as a Bifunctional Electrocatalyst for Overall Water Splitting and Anion Exchange Membrane Water-Electrolyzers

Abstract

Designing efficient and cost-effective bifunctional electrocatalysts for overall water splitting is burgeoning for sustainable hydrogen production. Though Pt−C and RuO2 are known as the state-of-the-art catalysts for electrochemical hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, it is essential to find alternatives based on cost-effective, efficient, and earth-abundant elements. In this direction, the present work explores nickel-based MXenes (Ni3C−F, where F indicates fluorinated terminal functional groups), a class of ceramic 2D-layered materials, as a bifunctional electrocatalyst toward OER and HER in alkaline media (1 M KOH). Further, the incorporation of cobalt into the Ni3C−F matrix modulates the electronic environments of the composite catalyst (Co−Ni3C−F), which improves its electrocatalytic activities toward both HER and OER. Studies reveal that to attain a 10 mA cm−2 current density, Co−Ni3C−F requires only ∼40 mV of extra overpotential as compared to the state-of-the-art catalysts for both HER (20 wt % Pt−C) and OER (RuO2) in an alkaline environment (1 M KOH solution). Moreover, the ηonset (OER−HER) and the η10 mA cm−2(OER−HER) values for the Co−Ni3C−F catalyst are ∼1.46 V (which is only 0.23 V extra as compared to the E0water splitting) and ∼1.62 V, respectively. Further, Co−Ni3C−F was used as an electrode material (both cathode and anode) in Anion Exchange Membrane Water-Electrolyzers (AEMWE), where, by applying 380 mA cm−2 current density, the cell potential reaches 2V. This offers an aspiration for the evolution of electrocatalysts in sustainable energy technologies.