Investigation of Mesoporous Niobium-Doped TiO2 as an Oxygen Evolution Catalyst Support in an SPE Water Electrolyzer

Titania doped by niobium was successfully synthesized via a modified evaporation-induced self-assembly method (EISA) as a support of IrO2 for a solid polymer electrolyte water electrolyzer (SPEWE). The doping amount of niobium (5, 10, 20 at. %) was emphatically investigated to evaluate the effects on nanostructure, morphology, and oxygen evolution reaction (OER) activity of Nb-doped titania supported IrO2. The high-resolution transmission electron microscopy (TEM) results show that IrO2 supported by Nb-doped titania exhibits grain refinement and uniform dispersion. An investigation of the electrocatalytic activity by half-cell electrochemical testing reveals that the Nb-doped titania supported IrO2 catalyst demonstrates significant OER activity. When the Nb content reaches 20 at. % in the support, the Nb-doped titania supported IrO2 possesses the highest OER activity, which is superior to that of pristine titania supported IrO2 and unsupported IrO2. The single-cell tests also prove that 20 at. % is the best Nb doping amount for titania supports of IrO2. It is found that the majority of the OER activity increase is due to the Nb-doping induced enhancement of the specific surface area and surface activity of transferring charge and species. The additional specific surface area and redox couples of Nb(IV)/Nb(V) are also responsible for this performance enhancement. Herein, the as-synthesized Nb-doped titania is considered to be a promising oxygen evolution catalyst support for SPEWE applications.