Study of fluorine doped (Nb,Ir)O2 solid solution electro-catalyst powders for proton exchange membrane based oxygen evolution reaction

Abstract

High surface area (∼300m2/g) nanostructured powders of (Nb1−xIrx)O2 and (Nb1−xIrx)O2:10F (∼100m2/g) have been examined as promising oxygen evolution reaction (OER) electro-catalysts for proton exchange membrane (PEM) based water electrolysis. Nb2O5 and 10wt.% F doped Nb2O5 powders were prepared by a low temperature sol-gel process which were then converted to solid solution (Nb,Ir)O2 and 10wt.% F doped (Nb,Ir)O2 [(NbIr)O2:10F] electro-catalysts by soaking in IrCl4 followed by heat treatment in air. Electro-catalyst powders of optimal composition (Nb0.75Ir0.25)O2:10F with ∼75at.% reduction in noble metal content exhibited comparable OER activity to commercial hydrated IrO2 and nanostructured in-house chemically synthesized IrO2. The (Nb,Ir)O2:10F electro-catalyst demonstrated excellent long term structural/corrosion stability comparable to in-house chemically synthesized pure IrO2:10F. First-principles calculations of the total energies, electronic structures and cohesive energies of the model systems have been performed and correlated to the excellent activity, long term stability of (Nb,Ir)O2:F for OER obtained experimentally.