Fluorine substituted (Mn,Ir)O2:F high performance solid solution oxygen evolution reaction electro-catalysts for PEM water electrolysis

Abstract

Identification and development of high performance with reduced overpotential (i.e. reduced operating electricity cost) oxygen evolution reaction (OER) electrocatalysts for proton exchange membrane (PEM) based water electrolysis with ultra-low noble metal content (i.e. reduced materials cost) is of significant interest for economic hydrogen production, thus increasing the commercialization potential of PEM water electrolysis. Accordingly, a novel electrocatalyst should exhibit low overpotential, excellent electrochemical activity and durability superior to state of the art noble metal based electro-catalysts (e.g. Pt, IrO₂, RuO₂). Herein, for the very first time to the best of our knowledge, exploiting first-principles theoretical calculations of the total energies and electronic structures, we have identified a reduced noble metal content fluorine doped solid solution of MnO₂ and IrO₂, denoted as (Mn_1−xIr_x)O₂:F (x = 0.2, 0.3, 0.4), OER electrocatalyst system exhibiting lower overpotential and higher current density than the state of the art IrO₂ and other previously reported systems for PEM water electrolysis. The doped solid solution displays an excellent electrochemical performance with a lowest reported onset potential to date of ∼1.35 V (vs. RHE), ∼80 mV lower than that of IrO₂ (∼1.43 V vs. RHE) and ∼15 fold (x = 0.3 and 0.4) higher electrochemical activity compared to pure IrO₂. In addition, the system displays excellent long term electrochemical durability, similar to that of IrO₂ in harsh acidic OER operating conditions. Our study therefore demonstrates remarkable, ∼60–80% reduction in noble metal content along with lower overpotential and excellent electrochemical performance clearly demonstrating the potential of the (Mn_1−xIr_x)O₂:F system as an OER electro-catalyst for PEM water electrolysis.